• 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)

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
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).

• 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?

• 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

You might take a look a the S-100 archives -- there was some work to put together a MSX system on S-100 cards.

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 :n8

• 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 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!

- VDP board: No composite output (RGB is not really useful nowadays)

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

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.

I thought that component video is widespread enough... 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

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.

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
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
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?

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

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?

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 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.