RetroBrew Computers Forum
Discussion forum for the RetroBrew Computers community.

Home » RBC Forums » General Discussion » MSX2 Compatible Computer Project
MSX2 Compatible Computer Project [message #4137] Tue, 23 January 2018 13:12 Go to next message
Sergey is currently offline  Sergey
Messages: 213
Registered: October 2015
Location: Portland, OR
Senior Member
Hi,

I'd like to build an MSX2 compatible computer. I'd like to share some of my ideas, and to get opinion of the forum members.

My goals/wishes for this project:
  • Follow MSX/MSX2 standards as close as possible
  • 128 KiB (or more) RAM
  • Yamaha V9938 VDP, 128 KiB Video RAM, composite and component outputs, with optional RGB output (header)
  • The main purpose would be running MSX/MSX2 games. With CP/M, FUZIX, possibly MSX-DOS support being the secondary goal
  • Two cartridge slots for game cartridges and hardware add-ons (e.g. MSX music, disk controller)
  • Use CBIOS
  • Implement a real keyboard. Likely using Cherry MX keys, and standard keycaps (a microcontroller based PS/2 adapter would be a backup option)

Design modularity and form factor options (which one would you prefer?):
  1. A single board with the entire computer implemented on it. Should be about 200 mm x 160 mm in size. Pros: most compact way, Cons: no modularity at all
  2. ECB based system. We already have an MSX (not MSX2) video board, that might somewhat help with developing this project, although a new V9938 based board would have to be implemented. Pros: individual boards can be used for other (non MSX) ECB systems. Cons: more expensive: DIN 41612 connectors, additional bus buffers, etc. Also not as compact
  3. Non-ECB backplane based system. Potentially built using 100 mm x 100 mm boards. Pros: cheaper than ECB, no need to adhere to ECB standard, can use some pins for MSX-specific signals (slot select, chip selects). Cons: well, not an ECB Smile
  4. Hybrid approach: Main board with CPU, 8255 (slot select, keyboard), I/O decode, sound/joystick, etc. Memory daughter board with SRAM and Flash and memory mapping/paging logic. And a video daughter board. Pros: modular enough, easier debug, a possibility of an upgrade path. For example it include TMS9918, V9938, and perhaps V9958 VDP; or MSX (no paging memory) and MSX2 (paging in slot 3).

Storage devices:
  • Floppy disk controller: include on board, or implement as a separate cartridge?
  • Storage: Flash disk (e.g. built using 39SF040), CF, or SD?
  • Perhaps it is possible to implement some kind of flexible cartridge emulation?

Thanks,
Sergey


[Updated on: Tue, 23 January 2018 13:15]

Report message to a moderator

Re: MSX2 Compatible Computer Project [message #4138 is a reply to message #4137] Tue, 23 January 2018 14:55 Go to previous messageGo to next message
danwerner is currently offline  danwerner
Messages: 23
Registered: October 2015
Junior Member
You might take a look a the S-100 archives -- there was some work to put together a MSX system on S-100 cards. S-100 has a pretty high entry point (with the power and card cage requirements), so I am not suggesting that is the way to go, but there is some work there that might be inspirational . . . . .

For me, I prefer a modular design -- it is easier to debug and the modules can be used for other projects which can lead to very interesting possibilities.

Dan
Re: MSX2 Compatible Computer Project [message #4139 is a reply to message #4137] Tue, 23 January 2018 16:39 Go to previous messageGo to next message
mscane is currently offline  mscane
Messages: 105
Registered: October 2015
Senior Member
Hi Sergey,

That sounds like a really interesting project.

Maybe an alternative could be to refresh the N8 design with some updates
( https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:n8 :n8Wink
  • Replace the existing TMS9918 video with a V9938 chip (that would give 80x25 video I believe)
  • Replace the 8255 keyboard interface with an 8242 PS/2 controller (like in the VGA3)
  • Change the compact flash interface to a bus connected IDE (in 8 bit mode)
  • Use an ATX style power connector
The N8 also included a floppy interface, SD card and sound chip.

Perhaps you could also consider changing the form factor to match one of the PC standards such as a Mini ITX (17 x 17 mm) or Micro ATX (224 x 224 mm).
That would allow you to use a wide range of ready made cases and power supply options.

I'm not sure how much use the ECB interface would be. As you have most peripherals on-board a bus connection become less important and the connector takes up a lot of space. Also, a lot of board space was taken up with the interfacing chips.

There was an S100 implementation of the V9938 video chip done a while ago:

http://s100computers.com/My%20System%20Pages/VDP%20Video%20B oard/VDP%20Board.htm

Cheers!

Max

Re: MSX2 Compatible Computer Project [message #4140 is a reply to message #4139] Tue, 23 January 2018 16:43 Go to previous messageGo to next message
danwerner is currently offline  danwerner
Messages: 23
Registered: October 2015
Junior Member
In order to get really good compatibility with MSX game roms, it would be good to avoid keyboard controllers and stick with an 8255 driven switch matrix keyboard. Converting the matrix to a PS/2 was one of the biggest issues with the N8 CBIOS and it is why many (most?) of the games need joystick and do not work with the keyboard.

Dan

[Updated on: Tue, 23 January 2018 16:44]

Report message to a moderator

Re: MSX2 Compatible Computer Project [message #4141 is a reply to message #4140] Tue, 23 January 2018 17:16 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
I think its a great idea. I always liked MSX and there are bits and pieces of MSX scattered in the N8, various ECB boards, and 3 S-100 boards (Z80 CPU, VDP, and Utility). However it never really matured into full blown MSX computer. My advice would be to start from a clean slate and target a full blown MSX computer. You could possibly reuse bits and pieces from the various MSX like board projects but it would probably be just as easy to just do a complete reboot of the idea. Best of luck!
Re: MSX2 Compatible Computer Project [message #4142 is a reply to message #4141] Tue, 23 January 2018 17:33 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 213
Registered: October 2015
Location: Portland, OR
Senior Member
Thank you for your feedback guys!

danwerner wrote on Tue, 23 January 2018 14:55
You might take a look a the S-100 archives -- there was some work to put together a MSX system on S-100 cards.


I've looked at them and got inspired Smile
But they have a few issues:
- Utility board: No MSX2 sub-slots, no memory paging
- VDP board: No composite output (RGB is not really useful nowadays)
- And as you've mentioned building an S-100 system to play MSX2 games is a bit of an overkill

mscane wrote on Tue, 23 January 2018 16:39
Hi Sergey,

Maybe an alternative could be to refresh the N8 design with some updates
( https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:n8 :n8Wink

  • Replace the existing TMS9918 video with a V9938 chip (that would give 80x25 video I believe)
  • Replace the 8255 keyboard interface with an 8242 PS/2 controller (like in the VGA3)
  • Change the compact flash interface to a bus connected IDE (in 8 bit mode)
  • Use an ATX style power connector

The N8 also included a floppy interface, SD card and sound chip.

Perhaps you could also consider changing the form factor to match one of the PC standards such as a Mini ITX (17 x 17 mm) or Micro ATX (224 x 224 mm).


I don't feel that N8 approach was a MSX compatible enough. Particularly where it comes to the memory/slots/sub-slots.

What is the reason to use 8242 keyboard controller (other than that PS/2 keyboards are widely available)? It seems that it would make the computer less MSX compatible. I suspect some programs, and especially games, would bypass BIOS and talk to the hardware directly.

Mini ITX / Micro ATX - no real benefit. How to fit MSX cartridge slots, or a bunch of I/O connectors an MSX would have? I can use an ATX power supply connector though...

The the floppy interface and 8-bit CF part makes sense

lynchaj wrote on Tue, 23 January 2018 17:16
I think its a great idea. I always liked MSX and there are bits and pieces of MSX scattered in the N8, various ECB boards, and 3 S-100 boards (Z80 CPU, VDP, and Utility). However it never really matured into full blown MSX computer. My advice would be to start from a clean slate and target a full blown MSX computer. You could possibly reuse bits and pieces from the various MSX like board projects but it would probably be just as easy to just do a complete reboot of the idea. Best of luck!


That is pretty much my idea.
Re: MSX2 Compatible Computer Project [message #4143 is a reply to message #4142] Wed, 24 January 2018 03:28 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
If you can us an integrated Z180 type chip and/or CPLD you probably could reduce the chip count and possibly the PCB space required. Depends on if Z180 type CPUs are MSX compatible though. Don't know if that's the case.
Re: MSX2 Compatible Computer Project [message #4322 is a reply to message #4137] Sat, 10 February 2018 08:43 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Any updates?
Re: MSX2 Compatible Computer Project [message #4326 is a reply to message #4322] Sun, 11 February 2018 09:16 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 213
Registered: October 2015
Location: Portland, OR
Senior Member
Not much... I have a preliminary schematic and I've started on keyboard PCB layout.
Pretty busy at work, so it will take time.

Thanks,
Sergey
Re: MSX2 Compatible Computer Project [message #4385 is a reply to message #4137] Thu, 22 February 2018 09:18 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Hi,
I would like to help to help on this project.
I had an msx when I was child and I remember few things, I learned them MSX-BASIC and Z-80 Assembler, even I cannot consider myself a software developer.

I was recently working by my part with the same goal.
Then I asked some people I fount through internet to share their designs with me (with us), but only one answered to me.
This guy developed some hardware, but I had not yet enough time to deep review it.
Perhaps he based his design on CPLD more than we would like but for sure we can take advantage from his work.
He also mentioned a ps2 keyboard converter.
He answered me with this link:
http://optotech.net.br/msx/ma_20_neos_kit2+/
Here is his main project page:
http://www.optotech.net.br/fzanoto/msx.htm

In addition I was looking for documentation and I think the best book to understand the msx hardware standard is this:
(joined text red book). I am still on the second chapter.
I don't know if any of you have it. I found that it is actually good to understand the circuit or bios code needed.

unfortunately it talks about the first standard (msx1) for the MSX2 standard I have this one, but I don't know if it's so good. (msx2 technical book).
One handicap with the schematics after msx1 is their pcb designs use a chip called msx engine (like yamaha S-1985, SMD and actually hard to found)
Perhaps we can replace them by a CPLD.
As I don't know how easy this could be, I also considered to initiate from the SVI 738 diagram who is almost an MSX2 but doesnt have that special chips (there are many places with upgrading to MSX2 instructions)


About the keyboard designer web is http://caro.su/msx/kbd4msx/y_yis503.htm (I dont know how good it could work)

I have some more documentation like MSX-DOS documentation (a CPM adapted version for MSX computers).

There is a Spanish guy who got the original source code and upgraded to an S.O. improved version called NEXTOR I don't know if open source or similar.
here is his software repository and his blog:
http://www.konamiman.com/msx/msx-e.html

I hope this helps.
J. Solis
Re: MSX2 Compatible Computer Project [message #4391 is a reply to message #4142] Sat, 24 February 2018 23:13 Go to previous messageGo to next message
traal is currently offline  traal
Messages: 2
Registered: February 2018
Junior Member
skiselev wrote on Tue, 23 January 2018 17:33
- VDP board: No composite output (RGB is not really useful nowadays)

RGBS alone is not so useful, but RGBHV (VGA) monitors are easy to find, even some that support 15kHz signals: 15khz.wikidot.com

I think component video wasn't popular outside the USA, even SCART doesn't support it AFAIK. (Edit: there's a standard pinout for it (green pin=Y, red pin=Pr, blue pin=Pb) but it isn't common.Wink

My vote is for composite (ugh) + RGBS/RGsB/RGBHV/YPrPb over HD15 like what the OSSC supports. Passive cables would then support composite, component, BNC (for professional Sony monitors), SCART, the VGA monitors listed in the link above, and the OSSC for DVI and HDMI. Not S-Video without a converter box but I think that's o.k. with all the other options.

[Updated on: Sun, 25 February 2018 10:11]

Report message to a moderator

Re: MSX2 Compatible Computer Project [message #4392 is a reply to message #4391] Sun, 25 February 2018 01:14 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 213
Registered: October 2015
Location: Portland, OR
Senior Member
Hi guys,

Thank you for your feedback!

jordi.solis wrote on Thu, 22 February 2018 09:18
Hi,
I would like to help to help on this project.
I had an msx when I was child and I remember few things, I learned them MSX-BASIC and Z-80 Assembler, even I cannot consider myself a software developer.

I was recently working by my part with the same goal.
Then I asked some people I fount through internet to share their designs with me (with us), but only one answered to me.
This guy developed some hardware, but I had not yet enough time to deep review it.
Perhaps he based his design on CPLD more than we would like but for sure we can take advantage from his work.
He also mentioned a ps2 keyboard converter.
He answered me with this link:
http://optotech.net.br/msx/ma_20_neos_kit2+/
Here is his main project page:
http://www.optotech.net.br/fzanoto/msx.htm

In addition I was looking for documentation and I think the best book to understand the msx hardware standard is this:
(joined text red book). I am still on the second chapter.
I don't know if any of you have it. I found that it is actually good to understand the circuit or bios code needed.

unfortunately it talks about the first standard (msx1) for the MSX2 standard I have this one, but I don't know if it's so good. (msx2 technical book).
One handicap with the schematics after msx1 is their pcb designs use a chip called msx engine (like yamaha S-1985, SMD and actually hard to found)
Perhaps we can replace them by a CPLD.
As I don't know how easy this could be, I also considered to initiate from the SVI 738 diagram who is almost an MSX2 but doesnt have that special chips (there are many places with upgrading to MSX2 instructions)


About the keyboard designer web is http://caro.su/msx/kbd4msx/y_yis503.htm (I dont know how good it could work)

I have some more documentation like MSX-DOS documentation (a CPM adapted version for MSX computers).

There is a Spanish guy who got the original source code and upgraded to an S.O. improved version called NEXTOR I don't know if open source or similar.
here is his software repository and his blog:
http://www.konamiman.com/msx/msx-e.html

I hope this helps.
J. Solis


Thanks for this information. MSX (not MSX 2) is fairly straight forward to implement using standard logic. You're right that MSX 2 implementation would be a bit more challenging, since most MSX 2 used an MSX engine IC, and that part I'll need to implement using either standard logic, or maybe using SPLDs. I found the MSX 2 databook with reference schematic, it is in Japanese, but I can read the schematic, and somehow translate the text using an online translator.
I'd like to have a native keyboard built using mechanical switches. It will be a header on the motherboard/CPU board connected to the PPI pins used for keyboard interface. And then it will be possible to either connect the mechanical keyboard (with a 4-to-10 decoder and open collector driver ICs on it), or a microcontroller based PS/2 interface.

traal wrote on Sat, 24 February 2018 23:13
skiselev wrote on Tue, 23 January 2018 17:33
- VDP board: No composite output (RGB is not really useful nowadays)

RGBS alone is not so useful, but RGBHV (VGA) monitors are easy to find, even some that support 15kHz signals: 15khz.wikidot.com

I think component video wasn't popular outside the USA, even SCART doesn't support it AFAIK.

My vote is for composite (ugh) + RGBS/RGsB/RGBHV/YPrPb over HD15 like what the OSSC supports. Passive cables would then support composite, component, BNC (for professional Sony monitors), SCART, the VGA monitors listed in the link above, and the OSSC for DVI and HDMI. Not S-Video without a converter box but I think that's o.k. with all the other options.


That is an interesting perspective. I thought that component video is widespread enough. I have it on all my TVs, and I think I've seen component to SCART converters... but I might be mistaken.
So what interfaces are available on the TVs outside of US nowadays? S-Video, SCART?

I can pin out RGBHV and composite... or S-Video and composite... But I really don't want to have 6 different connectors on the rear side of the board, and I also don't particularly like the idea of having headers + breakout cables Smile
As an option - I can connect the VDP outputs to a header, and then design one or more daughter boards that would connect to that header and convert VDP output to a usable format.
Re: MSX2 Compatible Computer Project [message #4394 is a reply to message #4392] Sun, 25 February 2018 10:26 Go to previous messageGo to next message
traal is currently offline  traal
Messages: 2
Registered: February 2018
Junior Member
skiselev wrote on Sun, 25 February 2018 01:14
I thought that component video is widespread enough... So what interfaces are available on the TVs outside of US nowadays? S-Video, SCART?

That's a good question. I've just asked it here. So far it seems composite and SCART were the most common in Europe.

skiselev wrote on Sun, 25 February 2018 01:14
I can pin out RGBHV and composite... or S-Video and composite... But I really don't want to have 6 different connectors on the rear side of the board, and I also don't particularly like the idea of having headers + breakout cables Smile

If you had some way to switch between RGBS/RGsB/RGBHV/YPrPb over the HD-15 connector in software or a DIP switch, then you would need only the 1 connector (+composite RCA). But yes, anyone who wants something better than composite would need a compatible VGA monitor or the right cable or converter box.

skiselev wrote on Sun, 25 February 2018 01:14
As an option - I can connect the VDP outputs to a header, and then design one or more daughter boards that would connect to that header and convert VDP output to a usable format.

That works too! You would just need to figure out how to make one case that can fit all the various connector types.
Re: MSX2 Compatible Computer Project [message #4395 is a reply to message #4394] Sun, 25 February 2018 12:16 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
we have to realize some details that were not listed by the MSX standard.
For example, the standard msx1 and msx2 do not mention anything about disk drives, however, while no one msx1 had a floppy disk drive integrated in the case, even no msx2 lacked of it.
These details may caused most manufacturers included a chip to integrate a big amount of resources in a new chip the MSX (2) engine.
Why they need to reduce the computer board size?
they use to sale those computers as keyboard, computer and floppy inside the case, like the apple II or the comodore Amiga 500.
J. Solis
Re: MSX2 Compatible Computer Project [message #4509 is a reply to message #4395] Sun, 25 March 2018 16:55 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Hi, As I live in europe I have my own opinion about composite output.
First, I think VPD s-100 board has RGB and also composite video output.
I used the composite video output on the SCGS card and it's full compatible with SCART with just a BNC to SCART converter. (about 4,00 €).
They are few RGB displays here but almost every 21" TV has SCART, VGA and HDMI, what's perfect to connect a pc, a raspberry and soon our msx2.

I hope this helps.
J Solis.
Re: MSX2 Compatible Computer Project [message #4516 is a reply to message #4509] Tue, 27 March 2018 09:03 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Hi all,
Are those schematics for an msx2+ useful for our project?
I don't know if you saw them before on the internet:
https://1drv.ms/f/s!AqjvpN-_7lyIgQjrDhz8OzK0krG8
folders:
TPC-310 is a MSX2 and it uses an msx2 engine.
Expert2p is an MSX2+ the good news is they don't need any msx2 engine chip, all of them I fount at utsource.

let me know
Jordi Solís.
Re: MSX2 Compatible Computer Project [message #4566 is a reply to message #4516] Thu, 12 April 2018 18:26 Go to previous messageGo to next message
ajacocks is currently offline  ajacocks
Messages: 15
Registered: November 2015
Junior Member
I think that this sounds like a fascinating project. I'd be very interested to see it move forward.
Re: MSX2 Compatible Computer Project [message #4602 is a reply to message #4566] Wed, 18 April 2018 07:53 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
I'm interested!
I am currently working on a Z80/Z180 based project with a modular setup. I have modules for CPU (Z80 and Z180), serial, V9958, PS2 keyboard/mouse,IDE module and an ROM/RAM module.
The idea is to make it MSX compatible. Next step is to change the ROM/RAM module for one which uses a MSX memory mapper and slot mechanism to select slots + ROMs.

Thanks for the Expert2 suggestion! The schematics are better readable than the Sony schematic a was trying to use.
Re: MSX2 Compatible Computer Project [message #4670 is a reply to message #4137] Tue, 01 May 2018 10:18 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Hi,
Here you are a link to download some good msx2 software, including an improved version of MSX-DOS 2 called NEXTOR or NBASIC some networking software, and also the whole MSX2 technical handbook in text files.

https://github.com/konamiman/msx

Konamiman and Daniel Berdugo also designed software and hardware of an MSX ethernet interface witch we can use later ;-)
http://obsonet.blogspot.com.es/

I hope this helps.

Jordi Solis
Re: MSX2 Compatible Computer Project [message #4685 is a reply to message #4137] Wed, 09 May 2018 04:52 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
skiselev wrote on Tue, 23 January 2018 16:12
Hi,

I'd like to build an MSX2 compatible computer. I'd like to share some of my ideas, and to get opinion of the forum members.

My goals/wishes for this project:


  • Follow MSX/MSX2 standards as close as possible
  • 128 KiB (or more) RAM
  • Yamaha V9938 VDP, 128 KiB Video RAM, composite and component outputs, with optional RGB output (header)
  • The main purpose would be running MSX/MSX2 games. With CP/M, FUZIX, possibly MSX-DOS support being the secondary goal
  • Two cartridge slots for game cartridges and hardware add-ons (e.g. MSX music, disk controller)
  • Use CBIOS
  • Implement a real keyboard. Likely using Cherry MX keys, and standard keycaps (a microcontroller based PS/2 adapter would be a backup option)



Design modularity and form factor options (which one would you prefer?):


  1. A single board with the entire computer implemented on it. Should be about 200 mm x 160 mm in size. Pros: most compact way, Cons: no modularity at all
  2. ECB based system. We already have an MSX (not MSX2) video board, that might somewhat help with developing this project, although a new V9938 based board would have to be implemented. Pros: individual boards can be used for other (non MSX) ECB systems. Cons: more expensive: DIN 41612 connectors, additional bus buffers, etc. Also not as compact
  3. Non-ECB backplane based system. Potentially built using 100 mm x 100 mm boards. Pros: cheaper than ECB, no need to adhere to ECB standard, can use some pins for MSX-specific signals (slot select, chip selects). Cons: well, not an ECB Smile
  4. Hybrid approach: Main board with CPU, 8255 (slot select, keyboard), I/O decode, sound/joystick, etc. Memory daughter board with SRAM and Flash and memory mapping/paging logic. And a video daughter board. Pros: modular enough, easier debug, a possibility of an upgrade path. For example it include TMS9918, V9938, and perhaps V9958 VDP; or MSX (no paging memory) and MSX2 (paging in slot 3).



Storage devices:


  • Floppy disk controller: include on board, or implement as a separate cartridge?
  • Storage: Flash disk (e.g. built using 39SF040), CF, or SD?
  • Perhaps it is possible to implement some kind of flexible cartridge emulation?



Thanks,
Sergey




Hi
Thinking more about this project. Any updates? I agree with the project goals and it should target 100% MSX2 compliance. Past projects always fell short and doomed them.

Regarding modularity, I like the hybrid approach. How to implement? ECB & S-100 is overkill. Making stackable PCBs (PC104) is difficult and parts expensive. Also the boards need to be big enough to provide enough room for components without extreme routing. I suggest a double wide euro board 160mmx200mm with holes in corners to mount. Then use right angle dip dual row headers and modified IDE cables as a bus. Maybe 2 or 3 bus connectors per board.

segregate the design into boards like (CPU + memory + 8255 + IO decode), (video, keyboard & mouse (MCU PS/2), sound), (IDE, SD, floppy drive)

keyboard should be switched matrix just like MSX design with header to separate keyboard PCB. I suggest cpu is Z180 class to reduce part count.

The idea is to separate CPU from IO functions so boards could be upgraded without scrapping whole stack but not be constrained like ECB and/or S-100. In theory a common IO stack could be used for non-MSX compatible CPU boards like 65xx, 68xx, 68030, etc. Something like C-128 switching between 6510 and Z80 processors.

[Updated on: Wed, 09 May 2018 12:04]

Report message to a moderator

Re: MSX2 Compatible Computer Project [message #4686 is a reply to message #4685] Wed, 09 May 2018 06:49 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Hi
another thing a modern MSX computer should have is Ethernet. There are some 8 bit Ethernet chips which I think would be compatible with Z80/Z180 type computer. Also 8 bit USB. I realize MSX standard did not include Ethernet or USB but are vital to modern computer connectivity.
Re: MSX2 Compatible Computer Project [message #4687 is a reply to message #4137] Wed, 09 May 2018 07:16 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Dear,
I think the Standard is on expansion.
they have some Ethernet in the market and others.
I attach you a link for a Spanish manufacturer web page.
He has Ethernet, PS/2 keyboard, four slot backplanes and more.
Look at this:
http://msx.deneb.nl/index.html

This is a expanded MSX (he say 100% ANSI compatible), perhaps you like this modular schema.

In my past posts I included a link to Nextor.
Nextor is an Operative System based on source code of ANSI MSX-DOS. So is an upgrade, if we go to a 100% standard we must think on use its software, rom bios, etc) I think remember one of it's upgrades is ethernet driver support.

What if we start copying an MSX2 design that we know is working and then we add modularity on the design.
J. Solis.
Re: MSX2 Compatible Computer Project [message #4688 is a reply to message #4687] Thu, 10 May 2018 05:12 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Hi
Of the MSX schematics I've looked at the SpectraVideo 738 (SVI 738) seemed to be the best. It is MSX (not MSX2) but I think it would make a good starting point. Even as a clone initially and once shown to work add more capability, full MSX2 compliance, etc.

another thing is the cartridge port should be on a dual row pin header not an edge connector directly connected to the main planar. The cartridge port needs to be securely mounted and insertion/removal of cartridges put a lot of strain on the PCB planar leading to failures. Along those lines, I suggest all the IO connectors should be dual row pin headers and connected by ribbon cables to the physical connector. It saves a lot of PCB space and decouples the PCB from the connecting cable. I think it is much more robust and reliable design.

One thing I'd like to see but have never gotten it work myself is a "community project site" with open access, configuration controlled schematics, software, etc. allowing multiple people to work on it at once.

Sergey: are you still interested in this project or has it gone dormant?
Re: MSX2 Compatible Computer Project [message #4689 is a reply to message #4688] Thu, 10 May 2018 11:03 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
lynchaj wrote on Thu, 10 May 2018 05:12
Hi
Of the MSX schematics I've looked at the SpectraVideo 738 (SVI 738) seemed to be the best. It is MSX (not MSX2) but I think it would make a good starting point. Even as a clone initially and once shown to work add more capability, full MSX2 compliance, etc.

another thing is the cartridge port should be on a dual row pin header not an edge connector directly connected to the main planar. The cartridge port needs to be securely mounted and insertion/removal of cartridges put a lot of strain on the PCB planar leading to failures. Along those lines, I suggest all the IO connectors should be dual row pin headers and connected by ribbon cables to the physical connector. It saves a lot of PCB space and decouples the PCB from the connecting cable. I think it is much more robust and reliable design.

One thing I'd like to see but have never gotten it work myself is a "community project site" with open access, configuration controlled schematics, software, etc. allowing multiple people to work on it at once.

Sergey: are you still interested in this project or has it gone dormant?


It seems the SVI 738 contains 2 ULA's, so not so usable as an example to build on.
Or did you mean SVI 728?
Re: MSX2 Compatible Computer Project [message #4690 is a reply to message #4689] Thu, 10 May 2018 11:42 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 213
Registered: October 2015
Location: Portland, OR
Senior Member
Andrew,

I am still interested in the project. But I am currently very busy with work and life (almost summer! so camping/hiking/climbing SmileWink. So probably the actual work will have to wait until later this year (September and on).

I do like some of the ideas above. I am not comfortable with using CPLDs/FPGAs. Using SPLDs might be OK.

I assume that various extensions, like Ethernet, USB and Flash/disk can be implemented as slots?

What are the advantages of using Z180? I don't think that Z80 design is too complicated. There is some I/O and memory decode logic, but other than that Z80 is very simple to interface with. Probably no advantage of higher CPU speed/clock either. Most of MSX/MSX2 software is designed to work with 3.58 MHz frequency anyway.

Thanks,
Sergey
Re: MSX2 Compatible Computer Project [message #4691 is a reply to message #4690] Fri, 11 May 2018 01:44 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
I am busy completing an add in cart for my current modular Z80/Z180 retro build. It should provide a MSX memory mapper (1MB), MSX slot/subslot mechanism, pageable FlashROM and 1 MSX catridge slot.
If it works I'll extend the design to include the CPU and make it into a SBC with slots for video and regular MSX slots.
Re: MSX2 Compatible Computer Project [message #4692 is a reply to message #4690] Fri, 11 May 2018 05:36 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
skiselev wrote on Thu, 10 May 2018 14:42
Andrew,

I am still interested in the project. But I am currently very busy with work and life (almost summer! so camping/hiking/climbing :)). So probably the actual work will have to wait until later this year (September and on).

I do like some of the ideas above. I am not comfortable with using CPLDs/FPGAs. Using SPLDs might be OK.

I assume that various extensions, like Ethernet, USB and Flash/disk can be implemented as slots?

What are the advantages of using Z180? I don't think that Z80 design is too complicated. There is some I/O and memory decode logic, but other than that Z80 is very simple to interface with. Probably no advantage of higher CPU speed/clock either. Most of MSX/MSX2 software is designed to work with 3.58 MHz frequency anyway.

Thanks,
Sergey

Hi Sergey,
OK. Enjoy your summer
Agree on the CPLD/FPGAs. On the Gryphon project we tried to consolidate some of the glue logic into a CPLD with mixed results. Based on that experience I would stick to 74xx type logic and maybe some common DIP GALs where they really work well. Trying to stuff too much into CPLDs and FPGAs just changes the problems without actually making things better. Also Gryphon (and N8) attempted to consolidate all the IO on one board and it just didn't work too well. I think it needs a better balance between consolidation and modularity.

I think the main advantage of the Z180 CPU is it has higher integration and can lead to lower chip count. Also it is capable of higher clock speed but would need to be clock selectable for compatibility sake. The N8 board used a Z180 and it worked well. I am not stuck on this point but it is an opportunity to simplify the design.

What I'd really like to see is a hybrid modular design which separates common IO into a couple of boards. One board for common storage functions (IDE, SD, Ethernet, USB, floppy, etc.) and another for user interface (video, audio, keyboard & mouse, joysticks, switches, etc.). Keep the processor & memory specific functions on a separate board with a standardized interface to the IO boards. S-100 has enough room but too complicated. ECB has a good interface but the PCBs are too small. A common IO stack could be reused across multiple projects not just Z80 MSX although that is a good starting point.

I think a cartridge slot is good but is mostly useful for EPROM cards and unusual/specialized devices. I would keep the common IO on the two IO boards and reserve the cartridges for games, applications, user customization, etc.

I think we can make something which increases PCB size and has a simpler less expensive expansion bus. For consideration, I think the 40 conductor ribbon cable (IDE) would work well. One 40 pin dual row header replicates the Z80 bus (as is) and another to carry the MSX unique chip selects & other miscellaneous signals. Power & ground may need a separate low impedance connection. Plus no need for a separate backplane PCB.

Glad to see the project is still alive.

[Updated on: Fri, 11 May 2018 05:51]

Report message to a moderator

Re: MSX2 Compatible Computer Project [message #4693 is a reply to message #4689] Fri, 11 May 2018 05:42 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
lintweaker wrote on Thu, 10 May 2018 14:03

It seems the SVI 738 contains 2 ULA's, so not so usable as an example to build on.
Or did you mean SVI 728?


Hi
Probably so. I recall the one used 74xx type logic not custom logic chips. It has been a while so my memory has faded. I recall studying it while working on the S-100 Z80 CPU board, S-100 VDP, and S-100 Utility board. The theory was to make an MSX like system for S-100 which had mixed success. However for this project those boards would serve as rich sources for component libraries and part footprints in KiCAD
Re: MSX2 Compatible Computer Project [message #4694 is a reply to message #4691] Fri, 11 May 2018 05:54 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
lintweaker wrote on Fri, 11 May 2018 04:44
I am busy completing an add in cart for my current modular Z80/Z180 retro build. It should provide a MSX memory mapper (1MB), MSX slot/subslot mechanism, pageable FlashROM and 1 MSX catridge slot.
If it works I'll extend the design to include the CPU and make it into a SBC with slots for video and regular MSX slots.


Hi
Is your design posted anywhere so I can see it? How far along is it?
Re: MSX2 Compatible Computer Project [message #4698 is a reply to message #4694] Sat, 12 May 2018 09:27 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Hi
My memory of the schematic was wrong. I think I used the Goldstar FC-200 as inspiration on the S-100 Utility.

Looking over the design it might make more sense to just implement the whole thing on a single planar PCB and use the cartridge port for expansion.
Re: MSX2 Compatible Computer Project [message #4699 is a reply to message #4698] Sat, 12 May 2018 11:37 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 108
Registered: March 2017
Senior Member
Hi Andrew,
Do you think is a wrong idea to use those schematics from another hobbyist?
they are MSX2 and MSX2+, I think.
https://1drv.ms/f/s!AqjvpN-_7lyIgQjrDhz8OzK0krG8

I think I have the eagle design too.

let me know.
Re: MSX2 Compatible Computer Project [message #4703 is a reply to message #4699] Sat, 12 May 2018 23:59 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
The Goldstar FC-200 service manual has nice detailed descriptions. Some parts are certainly usable as the form the basics of an MSX computer. Odd thing about the Goldstar, it mentions having Video Out on pin 16 of the catridge slot. That is non-standard. Normally pin 16 is a No Connect.

The Expert2 and 3 are very clear schematics to base an MSX2(+) on. Does anyone know if these schematics have ever been build?
I used the Expert2 schematic to base my memory mapper / slot /subslot mechanism on, hopefully there are no bugs in the schematic.
Re: MSX2 Compatible Computer Project [message #4705 is a reply to message #4699] Mon, 14 May 2018 04:59 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
jordi.solis wrote on Sat, 12 May 2018 14:37
Hi Andrew,
Do you think is a wrong idea to use those schematics from another hobbyist?
they are MSX2 and MSX2+, I think.
https://1drv.ms/f/s!AqjvpN-_7lyIgQjrDhz8OzK0krG8

I think I have the eagle design too.

let me know.


Hi
Can't access your files. Would you repost as a ZIP file attached to a message on forum?
Re: MSX2 Compatible Computer Project [message #4706 is a reply to message #4705] Mon, 14 May 2018 05:33 Go to previous messageGo to next message
pbirkel is currently offline  pbirkel
Messages: 61
Registered: October 2015
Member
All three folders in a single ZIP, attached.
Re: MSX2 Compatible Computer Project [message #4707 is a reply to message #4706] Tue, 15 May 2018 05:42 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Thanks for posting the ZIP file.

I think I am going to wait until Sergey gets back and then follow his lead on this. It will be interesting where this project goes.
Re: MSX2 Compatible Computer Project [message #4708 is a reply to message #4707] Tue, 15 May 2018 08:35 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
My "MSX mapper / slot mechnism / BIOS ROM / MSX cartridge slot" PCB is now being made in China. I used SMD for all 74-series chips, never done that before. Let's see how it turns out.
Re: MSX2 Compatible Computer Project [message #4709 is a reply to message #4708] Wed, 16 May 2018 06:47 Go to previous messageGo to next message
lynchaj is currently offline  lynchaj
Messages: 454
Registered: June 2016
Senior Member
Hi
Would you post your design here in the forum. It would help see what you are developing.
Re: MSX2 Compatible Computer Project [message #4710 is a reply to message #4709] Thu, 17 May 2018 02:57 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
Hi,

As soon as my setup has enough of the MSX hw and can run C-BIOS I can start thinking about creating on github and sharing it. So hopefully in the coming months.
Re: MSX2 Compatible Computer Project [message #4757 is a reply to message #4710] Wed, 13 June 2018 09:18 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
So I got my MSX mapper / slot mechnism / BIOS ROM / MSX cartridge slot" PCB and soldered all the components. Unfortunately there are some issues I tried to debug but so far could not fix.
What works:
- slot/subslot mechanism through the PPI
- booting from Flash ROM
- 1Mbit Flash ROM mapped in 32k blocks to slot 0-0, 0-1, 0-2 and 0-3
- Memory mapper (not fully tested), see below

What does not work / has issues:
- Memory, seemingly due to timing issue.
- Somehow IO port reads has issues while write IO ports works just fine (V9958 video works)

I am now preparing a new revision of the PCB with much more test points and mostly DIP chips only. If there is interested I can post the current schematic for some feedback.
Re: MSX2 Compatible Computer Project [message #4830 is a reply to message #4757] Sat, 30 June 2018 12:29 Go to previous messageGo to previous message
lintweaker is currently offline  lintweaker
Messages: 64
Registered: April 2018
Member
New SBC style boards are in, managed to get MSX1 working! Even starts a game from a slot 0 subslot in the same flash. The board has some issues so a respin is needed.
First build a PS/2 to parallel keyboard converter.
Previous Topic: Registering for wiki and resetting passwords not working?
Next Topic: New eZ80 Small Encased System


Current Time: Fri Sep 25 22:11:32 PDT 2020

Total time taken to generate the page: 0.01618 seconds