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Re: MSX2 Compatible Computer Project [message #6750 is a reply to message #6749] Mon, 11 November 2019 08:28 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Sergey,

I've been looking over the schematic on your GitHub page. But I'm having a problem in understanding where you're generating the 3.58mhz clock. Looks like you have an optional PAL clock. And that you generate the frequency for the VDP as well as the RTC. But I'm not seeing where on the schematic you are generating this signal from. I'm guessing that you're probably dividing the 21.477270mhz clock by 6. But I'm not actually seeing it on the schematic. What am I missing here?

jordi.solis wrote on Mon, 11 November 2019 04:53
Hi people.
there's another MSX project witch you can buy to Eugeny Brychkov who includes MSX official license.
maybe you can ask him.
here you are the project: http://www.gr8bit.ru/what-is-gr8bit.htm
I'm familiar with that project. But not sure how it's really relevant to this thread...other than they are both duplicating the MSX standard. I agree that it would be nice to have a sanctioned bios. But considering Sergey doesn't seem interested in jumping through the hoops required to try and obtain the licensing from ASCII or Microsoft, and there is another option (C-Bios), as well as two known compatible bios (Sanyo PHC-23J and Philips NMS 8250) according to the documentation, this is a moot point in my opinion. And while the gr8bit might be neat in that it can be shoved into a ATX computer case, whereas this currently doesn't have a case. But even this point is not a huge issue, as I am planning on designing a 3D-printable case for this computer and releasing the design files for any who wish to build it. Of course any number of others could also submit their own designs...it's nice to have options. Then there is the issue that with the amount of PCBs required to build the gr8bit, I hazard a guess that it would ultimately be a little more expensive to get up and running. (Just checked, $499 for the kit... Quite a bit more expensive) Not to mention it is at least partially emulating hardware with FPGAs. It just seems like that project has completely different goals to this one. What Sergey has done here is a clone that is faithful to the original in spirit and design.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard

[Updated on: Mon, 11 November 2019 08:33]

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Re: MSX2 Compatible Computer Project [message #6751 is a reply to message #6750] Mon, 11 November 2019 08:56 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
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jdgabbard wrote on Mon, 11 November 2019 17:28
Sergey,

I've been looking over the schematic on your GitHub page. But I'm having a problem in understanding where you're generating the 3.58mhz clock. Looks like you have an optional PAL clock. And that you generate the frequency for the VDP as well as the RTC. But I'm not seeing where on the schematic you are generating this signal from. I'm guessing that you're probably dividing the 21.477270mhz clock by 6. But I'm not actually seeing it on the schematic. What am I missing here?
The (CPU) clock signal is generated by the VDP from the 21.x MHz crystal.
Re: MSX2 Compatible Computer Project [message #6752 is a reply to message #6751] Mon, 11 November 2019 10:01 Go to previous messageGo to next message
bifo is currently offline  bifo
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gr8bit isn't too relevant to this project, but the fact that the man who is control of the MSX licensing and the BIOS for it is open minded to hobbyist projects is definitely relevant. If you get in touch with him I'm sure he'll give the green light to using the MSX BIOS. He's given the green light to far more expensive FPGA systems in the past.
Re: MSX2 Compatible Computer Project [message #6753 is a reply to message #6751] Mon, 11 November 2019 10:59 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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lintweaker wrote on Mon, 11 November 2019 08:56
jdgabbard wrote on Mon, 11 November 2019 17:28
Sergey,

I've been looking over the schematic on your GitHub page. But I'm having a problem in understanding where you're generating the 3.58mhz clock. Looks like you have an optional PAL clock. And that you generate the frequency for the VDP as well as the RTC. But I'm not seeing where on the schematic you are generating this signal from. I'm guessing that you're probably dividing the 21.477270mhz clock by 6. But I'm not actually seeing it on the schematic. What am I missing here?
The (CPU) clock signal is generated by the VDP from the 21.x MHz crystal.
Ok, that makes a little more sense now.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6754 is a reply to message #6752] Mon, 11 November 2019 11:00 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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And that begs the question of whether part of the cost is due to the licensing... While I doubt it, with all the "Mini" retro consoles coming out in the last few years, I can't help but think there may be a similar effort on the MSX front.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6755 is a reply to message #6754] Mon, 11 November 2019 11:55 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Well, I shot an email over to opensource@microsoft.com to see if I could persuade them to release the MSX-BASIC source like they did with the DOS 1 & 2 last year. If they will release the MSX-BASIC code, that is one hurdle. Not to mention how important it is for computer history in general. Maybe someone could track down the current contact information for the MSX Licensing Corp. and we could send a request to them as well. Last I heard, all efforts to recommercialize the MSX have been halted due to the failure of the One-Chip-MSX. So they may be willing to just release it into the wild.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6758 is a reply to message #6725] Tue, 12 November 2019 00:27 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
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hello lintkeaker!
How was your virtual floppy project?
Did you get it to work?
In your post you told "it can be used as a (virtual) disk drive", does it mean we could have more uses just by programming that Raspberry? something like a wifi network interface?
J. S.
Re: MSX2 Compatible Computer Project [message #6762 is a reply to message #6758] Wed, 13 November 2019 08:36 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
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jordi.solis wrote on Tue, 12 November 2019 09:27
hello lintkeaker!
How was your virtual floppy project?
Did you get it to work?
In your post you told "it can be used as a (virtual) disk drive", does it mean we could have more uses just by programming that Raspberry? something like a wifi network interface?
J. S.
I am busy writing the BIOS code for the MSX side so I will appear as (a) normal (large)floppy drive(s). Luckily on the Pi side the existing code is very usable and is already working.
With the hardware there are lots more possibilities as long the required software will be created. A wireless network interface is an example.
Re: MSX2 Compatible Computer Project [message #6763 is a reply to message #4137] Wed, 13 November 2019 12:49 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Sergey,

Forgive me, as I'm not very acquainted with the MSX architecture. Concerning compatibility with the PHC-23J and the NMS-8250, are any features lost when using one or the other? Specifically concerning the memory. My understanding of the MSX bios is that it automatically looks for memory in each slot/sub. However I see the the PCH doesn't have a mapper, while the NMS does have a 128k mapper. Any issue with reading the full range of memory with these BIOS's? I doubt it would, but you never can tell what companies do when changing the bios for their own purpose. The reason I ask, is that while C-Bios is open source, it currently lacks 100% compatibility, and doesn't have cassette routines from what I read. So that would make the preferred BIOS of choice the NMS in my opinion.

Second question, as I understand it, most mappers allow you to control each 16k page in a Slot. But from what I'm reading in your documentation it would appear that you mapped this to a single 64k page in slot 3-2. Is that correct?


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6765 is a reply to message #6763] Wed, 13 November 2019 15:53 Go to previous messageGo to next message
etchedpixels is currently offline  etchedpixels
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MSX has three layers of memory management. It's the most broken, catastrophic fail of a design in that respect and that's why even many games don't work on every MSX.

In the beginning (pre MSX) each 16K bank could be one of four slots. Two GPIO bits select which. Almost nice and simple.

MSX1 extended this with a crazy hack that uses memory address 0xFFFF in each bank to further change which of four subslot chunks appear in each 16K slot. That's a nightmare because you then have to get 0xFFFF in the relevant slot mapped to change the subslot and do it without unmapping something you need. The ROM can do it for some banks only. To add to the excitement MSX1 didn't do the sane thing and decide where the RAM goes, so your RAM might be slot, subslot or smeared around several. That was apparently not painful enough so the disks and other I/O devices also use slots and subslots so that trying to copy data from 0x4000 in subslot 2 of slot 3 to an SD card with MMIO at 0x4000 in subslot 1 of slot 1 is a barrel of laughs.

MSX2 then puts a third layer (an actual vaguely sane banking system) for the RAM only on top of it all. It has to be back compatible so couldn't presumably replace the original misdesign. Thus you map the RAM (once you find it) into the right places and the mapper then determines vaguely sanely what you see through that window.

In practice that usually means that except for I/O (which is still terminally broken) you map the RAM over most of your address space, leave it as is and use the mapper.

Alan
Re: MSX2 Compatible Computer Project [message #6766 is a reply to message #6763] Wed, 13 November 2019 15:56 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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jdgabbard wrote on Wed, 13 November 2019 12:49

Concerning compatibility with the PHC-23J and the NMS-8250, are any features lost when using one or the other?
The only reason I picked these machines, is that they seem to be good enough generic MSX2 systems with the slot configuration similar to Omega. PHC-23J BIOS configures VDP for NTSC video output (60 Hz refresh rate) and NMS-8250 BIOS configures VDP for PAL video output (50 Hz refresh). That's pretty much all the differences that I know of.

Quote:

Specifically concerning the memory. My understanding of the MSX bios is that it automatically looks for memory in each slot/sub. However I see the the PCH doesn't have a mapper, while the NMS does have a 128k mapper. Any issue with reading the full range of memory with these BIOS's?
While it is possible that MSX2 BIOS automatically checks slots for memory/ROM extensions, it appears that it still expects to find RAM at the standard location. At least if I move RAM mapper to a different slot, MSX2 BIOS will no longer boot... C-BIOS actually auto-detects RAM location, and will boot as long as the RAM is available.
As far as I know all MSX2 machines had a memory mapper. I actually haven't checked if these MSX2 ROMs detect the whole 512 KiB of memory... I should check that.

Quote:

The reason I ask, is that while C-Bios is open source, it currently lacks 100% compatibility, and doesn't have cassette routines from what I read. So that would make the preferred BIOS of choice the NMS in my opinion.
C-BIOS functionality is pretty much limited to running software (games?!Wink from ROM cartridges. NMS is not the best option, since your TV is probably NTSC, also being originally a Japanese platform, most games expect 60 Hz refresh (and retrace interrupt), and will run somewhat slower on PAL system.

Quote:

Second question, as I understand it, most mappers allow you to control each 16k page in a Slot. But from what I'm reading in your documentation it would appear that you mapped this to a single 64k page in slot 3-2. Is that correct?
In MSX slots and memory pager are two different things ;-)
It is a bit confusing, but basically, it works in three layers:
Layer 1 & 2 - Primary and Expanded slots. There are 4 primary slots, each one can have an extended slot behind it. In case of Omega, only slot 3 is expanded. Although it is possible to install slot expanders in the external cartridge slots.
Each slot can have 4 x 16 KiB memory blocks, starting at 0x0000, 0x4000, 0x8000, and 0xC000. The slot mechanism allows choosing which one of these memory blocks gets mapped to the CPU memory space. But it does not allow mapping these blocks at different addresses. For example, you can map slot 0 0x0000-0x3FFF to the CPU memory space 0x0000-0x3FFF.
Now, the memory pager occupies an entire slot (3-2 in case of Omega), and it allows mapping any one of 16 KiB RAM pages to any one of these 4 memory blocks.
RAM mapping looks something like this:
[CPU]->[Slot 3]->[Sub-Slot 2]->[Memory Pager]->[SRAM]
Other than RAM memory pagers, there are also so called MegaROM cartridges. These are normally used for MSX2 games, that use 128 KiB (1 megabit) or bigger ROMs. In this case the mapper is usually somewhat simpler, and maps only two 16 KiB pages of ROM to the slot.

Hope this helps ;-)
Sergey

[Updated on: Wed, 13 November 2019 18:14]

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Re: MSX2 Compatible Computer Project [message #6767 is a reply to message #6766] Wed, 13 November 2019 18:10 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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Hehe... Alan beat me to it, and probably explained the MSX2 memory architecture a bit better ;-)
But now you can compile both replies together, and get even more complete picture...
Re: MSX2 Compatible Computer Project [message #6770 is a reply to message #6767] Thu, 14 November 2019 06:36 Go to previous messageGo to next message
etchedpixels is currently offline  etchedpixels
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The only other bits worth noting is that there are also MegaRAM boards that sort of work like the MegaROM and were used particularly in Brazil on MSX1 to get usable banked memory (and primarily to pirate cartridges...Wink. It's also possible to add a mapper to an MSX1 machine, or a VDP9938 to an MSX1 machine or both, just to maximise confusion Cool

Re: MSX2 Compatible Computer Project [message #6772 is a reply to message #6766] Thu, 14 November 2019 07:27 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Sergey wrote on Wed, 13 November 2019 15:56

C-BIOS functionality is pretty much limited to running software (games?!Wink from ROM cartridges. NMS is not the best option, since your TV is probably NTSC, also being originally a Japanese platform, most games expect 60 Hz refresh (and retrace interrupt), and will run somewhat slower on PAL system.
I'm somewhat familiar with mappers and the IO/Addresses that they use. I do have an MSX1, along with a mega ram cart (SD-512). So I understand the gist of how they generally work. My question was more towards the specific hardware of the Omega, and the BIOS. Mostly whether it was capable of banking in the ram in 16k chunks, in the random order. Thanks for addressing that part. Now it seems that the question of whether those BIOS's recognize the entire memory area. Since one only has 64k of memory that it would normally see in that Sub, and the other has a Mapper capable of addressing the 128k. That is something I can't answer at the moment.

As for the above quote, it seems that NMS would still be the best option, though it would just require a patch. Again, I'm not completely familiar with the MSX Bios, but my understanding is that it should come down to correcting a couple of values in ROM that are written to the registers. One would need to disassemble the bios into a listing and compare it with the available documentation to figure out which bytes to patch. But that may still be an option. My only other fear is that PHC-23J bios will not see the additional memory. Not all MSX2 computers had a mapper. And the PHC-23J is specifically one that DOES NOT, it only has a total of 64k of memory, according to the MSX.org page. So the question is, does the PHC-23J recognize the extra available memory. And if not, it may be useful to have a patched BIOS for the NMS, or potentially find another MSX2 bios that is comparable.

I'll take a look and see if I can track down another machine that may work.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6773 is a reply to message #6772] Thu, 14 November 2019 07:38 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
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Regarding the PHC-23J, the one with the Yamaha S1985 as engine has a memory mapper. Not sure if the PHC-23J without memory mapper still has a BIOS with memory mapper code (I think it has).
Re: MSX2 Compatible Computer Project [message #6774 is a reply to message #6773] Thu, 14 November 2019 08:38 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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lintweaker wrote on Thu, 14 November 2019 07:38
Regarding the PHC-23J, the one with the Yamaha S1985 as engine has a memory mapper. Not sure if the PHC-23J without memory mapper still has a BIOS with memory mapper code (I think it has).
I stand corrected. It looks like the PHC-23J uses either the S1985 or the S3527, both of which have mappers according the the datasheets. So this is a non-issue. And looks like the PHC-23J BIOS should be a good fit.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6775 is a reply to message #6774] Thu, 14 November 2019 17:29 Go to previous messageGo to next message
bifo is currently offline  bifo
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jdgabbard wrote on Thu, 14 November 2019 08:38
lintweaker wrote on Thu, 14 November 2019 07:38
Regarding the PHC-23J, the one with the Yamaha S1985 as engine has a memory mapper. Not sure if the PHC-23J without memory mapper still has a BIOS with memory mapper code (I think it has).
I stand corrected. It looks like the PHC-23J uses either the S1985 or the S3527, both of which have mappers according the the datasheets. So this is a non-issue. And looks like the PHC-23J BIOS should be a good fit.
Glad this was resolved, but curiously when I was looking at the NMS-8250 page on the MSX wiki, I saw that it was a badge-engineered Sanyo Wavy25, which was an MSX2 with only 64k as well. The NMS (and a few other badge engineered models) got 128k.
Re: MSX2 Compatible Computer Project [message #6776 is a reply to message #6775] Thu, 14 November 2019 23:04 Go to previous messageGo to next message
lintweaker is currently offline  lintweaker
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Only for completeness: the S3527 does not have a mapper function (see datasheet, IO ports for the mapper are missing). It was more of a engine for MSX1.
Re: MSX2 Compatible Computer Project [message #6777 is a reply to message #6776] Fri, 15 November 2019 08:10 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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lintweaker wrote on Thu, 14 November 2019 23:04
Only for completeness: the S3527 does not have a mapper function (see datasheet, IO ports for the mapper are missing). It was more of a engine for MSX1.

Yeah, looks like you're right. The S3527 does have an expanded SLOT 3 (as well as SLOT 0), but it doesn't have a mapper to bank in the memory. I imagine the BIOS is still the same unless there was a revision. So it probably is still capable of detecting the memory on the Omega.

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Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6799 is a reply to message #4137] Mon, 18 November 2019 08:29 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Sergey,

Any idea what type of power consumption this uses? I'm guessing it would be sub-2A. But that is just a guess.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6801 is a reply to message #6799] Mon, 18 November 2019 11:48 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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Hi Doug,

If I recall correctly, I've measured about 750mA. So 5V / 2A power supply should be plenty.
Note, that if you connect cartridges, they will consume some power too.
Also note that with 5V power supply the board will not supply +12V / -12V voltages to cartridge slots. If you're planning to use cartridges that use 12V/-12V, you'll have to use a power supply that can provide all three voltages, and connect it to the connector J10.

Thanks,
Sergey
Re: MSX2 Compatible Computer Project [message #6802 is a reply to message #6801] Mon, 18 November 2019 13:01 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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The reason I ask is, mentioned before, I plan on designing a case for this. And integrating a PSU is something I have in mind. I'm throwing together a small 12-5-/12 PSU design to connect through an IEC connector for testing. And just need to have an idea as the the current draw.

Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6804 is a reply to message #6802] Mon, 18 November 2019 13:34 Go to previous messageGo to next message
bifo is currently offline  bifo
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A 5v 2a psu is USB level power, that seems wrong. It's definitely easy to find a suitable supply but I don't know about anyone else, I can't solder a USB plug. Please don't make it more difficult than it needs to be, I can do the 5v power plug from the easyz80 i built, but frankly a 9 volt center negative would be ideal.
Re: MSX2 Compatible Computer Project [message #6805 is a reply to message #6802] Mon, 18 November 2019 13:39 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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There are two options for 5V/12V/-12V power supplies:

1. Power supply module that goes inside the case, for example Mean Well RT-50B (https://www.mouser.com/ProductDetail/709-RT50B) or Mean Well RT-65B (https://www.mouser.com/ProductDetail/709-RT65B).
2. Power brick and a cable to connect that power brick to the on-board 8-pin power connector. For example Mean Well GP25B13D-R1B (https://www.mouser.com/ProductDetail/709-GP25B13D-R1B) with 5 pin DIN panel mount connector (https://www.mouser.com/ProductDetail/161-0005-E). The DIN power connector can be soldered directly to the main board using short pieces of wire, or it is possible to make a short cable with 8-pin connector on the other end for more modular construction.

If you go with the second option, it might be possible to use the same case design for both 5V and 5V/12V/-12V options, with just a little modification for the power jack hole.

Re: MSX2 Compatible Computer Project [message #6806 is a reply to message #6804] Mon, 18 November 2019 13:43 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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bifo wrote on Mon, 18 November 2019 13:34
A 5v 2a psu is USB level power, that seems wrong. It's definitely easy to find a suitable supply but I don't know about anyone else, I can't solder a USB plug. Please don't make it more difficult than it needs to be, I can do the 5v power plug from the easyz80 i built, but frankly a 9 volt center negative would be ideal.
Omega uses the same 5V DC jack used in Easy Z80. 9V won't work, as the main board does not include voltage regulator (you must supply regulated 5V).
USB chargers that supply 5V/2V should work just fine, given that a suitable USB Type A to DC barrel cable is used (e.g. https://www.amazon.com/Onite-5-5x2-1mm-Positive-Electronic-O rganorgan/dp/B01MZ0FWSK)
Re: MSX2 Compatible Computer Project [message #6807 is a reply to message #6802] Mon, 18 November 2019 14:02 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
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About this.
I personally would prefer a box prepared to house a 3.5 "floppy disk drive before integrating the power supply.

Although I have no idea of the consumption in + 12v and -12v that MSX cartridges may need, you can take advantage of the circuit attached.
This was among the old retrobrew files. It is an interface for MSX cartridges that is part of the N8VEM computer, which is powered only by 5v.
This circuit contains some ICs that provide the required voltages.

To power the disk drive that I mention would require more power in that PSU.
It would be necessary to review how the old MSX2 solved it.
Well, I hope my find helps.

Jordi Solis
Re: MSX2 Compatible Computer Project [message #6808 is a reply to message #6807] Mon, 18 November 2019 14:24 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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jordi.solis wrote on Mon, 18 November 2019 14:02

To power the disk drive that I mention would require more power in that PSU.
It would be necessary to review how the old MSX2 solved it.
3.5" drives only use 5V power supply. So unless you really need +12V/-12V, a powerful enough 5V supply will do. Thankfully the technology had advanced since mid-80's and fairly compact and inexpensive 5V/4A (and even 5V/6A) switching power supplies are now available.

Old MSX/MSX2 systems used linear power supplies with multiple secondary windings to produce the required voltages. Bulky, expensive, noisy, and inefficient...
Re: MSX2 Compatible Computer Project [message #6809 is a reply to message #6808] Mon, 18 November 2019 14:25 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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Sergey wrote on Mon, 18 November 2019 14:24
jordi.solis wrote on Mon, 18 November 2019 14:02

To power the disk drive that I mention would require more power in that PSU.
It would be necessary to review how the old MSX2 solved it.
3.5" drives only use 5V power supply. So unless you really need +12V/-12V, a powerful enough 5V supply will do. Thankfully the technology had advanced since mid-80's and fairly compact and inexpensive 5V/4A (and even 5V/6A) switching power supplies are now available.

Old MSX/MSX2 systems used linear power supplies utilizing transformers with multiple secondary windings to produce the required voltages. Bulky, expensive, noisy, and inefficient...
Re: MSX2 Compatible Computer Project [message #6810 is a reply to message #6807] Mon, 18 November 2019 14:30 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
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ups! my answer was too late.
I bet for the power brick.
Re: MSX2 Compatible Computer Project [message #6815 is a reply to message #6805] Tue, 19 November 2019 07:28 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
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Sergey wrote on Mon, 18 November 2019 13:39
There are two options for 5V/12V/-12V power supplies:

1. Power supply module that goes inside the case, for example Mean Well RT-50B (https://www.mouser.com/ProductDetail/709-RT50BWink or Mean Well RT-65B (https://www.mouser.com/ProductDetail/709-RT65BWink.
2. Power brick and a cable to connect that power brick to the on-board 8-pin power connector. For example Mean Well GP25B13D-R1B (https://www.mouser.com/ProductDetail/709-GP25B13D-R1BWink with 5 pin DIN panel mount connector (https://www.mouser.com/ProductDetail/161-0005-EWink. The DIN power connector can be soldered directly to the main board using short pieces of wire, or it is possible to make a short cable with 8-pin connector on the other end for more modular construction.

If you go with the second option, it might be possible to use the same case design for both 5V and 5V/12V/-12V options, with just a little modification for the power jack hole.

Both of those options are rather large to fit into a case and still have it aesthetically pleasing. I was thinking about something much smaller. Even the Pico-ATX PSUs that you can buy cheap on ebay for $10-20 are only 53x37mm, and provide 12v @ 8A, -12v @ 0.1A, 5v @ 8A (+1.5A Standby). Now granted you'd need a 12v Power Brick rated high enough to supply the Pico PSU. But realistically, that would likely only need to be in the area of 4 Amps. But this might also be a better solution to those who do not want to mess around with mains power.

I might go ahead and order one of these Pico PSUs to test with. I'm mostly concerned with how hot the PSU may get, as it doesn't have any mounting holes. Meaning I'd need to figure out how to secure it in the case. But being a switch mode supply I doubt it would be getting too hot. Either way, it seems like a valid solution, and I'm guessing has an integrated PS_On signal (I just looked at the manual, and verified this signal is present). Meaning that it may be as simple as using a Molex cable adapter and running the PS_On and a GND to the back of the case for a power switch.

Mind you, I'm still playing with this in my head, and it might be easy to just use a 12v Brick, with a small board to regulate a 5v supply, and a charge pump circuit to get the -12v reference. I'm just not sure how much current a cartridge that needs -12v would use.

Edited for update.

-Doug.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard

[Updated on: Tue, 19 November 2019 07:38]

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Re: MSX2 Compatible Computer Project [message #6816 is a reply to message #6815] Tue, 19 November 2019 07:49 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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Registered: October 2015
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Doug,

Maybe I wasn't clear on the second option. You don't need to fit the power supply in this case. Just a DIN connector and a few wires.

Although, your idea with using a small board and 12V input voltage should work too. To get 5V from 12V it is possible to use a high efficiency DC-DC converter, e.g. https://www.mouser.com/ProductDetail/580-OKI78SR5-1.5W36C. For -12V, it might be possible to use LT1054 based charge pump converter. See the schematic Jordi shared above.

- SK
Re: MSX2 Compatible Computer Project [message #6835 is a reply to message #6816] Sun, 24 November 2019 05:21 Go to previous messageGo to next message
andrii_kutepov is currently offline  andrii_kutepov
Messages: 25
Registered: November 2015
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Sergey,

As you know i collect part for Omega build.
On githab i can read:

"V9958 VDP Support
The Omega Main Baord can be configured to support either V9958 VDP (recommended) or V9938 VDP. To support V9958 VDP the board should be configured as follows:

Do not install the following components:
Transistor: Q2
Capacitor: C43.."

Where C43 are Worth ?
Re: MSX2 Compatible Computer Project [message #6836 is a reply to message #6835] Sun, 24 November 2019 10:21 Go to previous messageGo to next message
Sergey is currently offline  Sergey
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Registered: October 2015
Location: Portland, OR
Senior Member
C43 is a bypass capacitor for U43. If you'd like to have PAL support, you'll want to have U43 and C43.
It doesn't hurt to have it installed anyway, even if you don't want to have PAL or V9938 support.


Re: MSX2 Compatible Computer Project [message #6843 is a reply to message #6836] Tue, 26 November 2019 20:56 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
Messages: 62
Registered: March 2016
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Sergey,

I was going over the BOM, and noticed an error. For R27-33 you have listed 6 - 1k resistors. And at first, it didn't appear there was a R29, which would make the BOM correct. However, on v1.1 you do have an R29, which connects to pin 8 of U42 and VCC. That said, I'm assuming this is also a 1k value. But I didn't notice it mentioned on the BOM, or in any of the optional instructions. I'm thinking this just needs the BOM updated to note 7 - 1k resistors instead of the 6.

-Doug.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6844 is a reply to message #6843] Tue, 26 November 2019 21:35 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 212
Registered: October 2015
Location: Portland, OR
Senior Member
jdgabbard wrote on Tue, 26 November 2019 20:56

I'm thinking this just needs the BOM updated to note 7 - 1k resistors instead of the 6.
Yes it should be 7 x 1k resistors. I've updated the Bill of Materials.
Thank you for your feedback!
Re: MSX2 Compatible Computer Project [message #6845 is a reply to message #6844] Thu, 28 November 2019 07:58 Go to previous messageGo to next message
jdgabbard is currently offline  jdgabbard
Messages: 62
Registered: March 2016
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Sergey,

Another correction for you. Under the Mainboard Building Instructions document, in the Optional Components Section, you state "8087 math co-processor U1 is completely optional". I'm assuming this is a remnant from using the Xi-8088 version as a template.

-Doug.


Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
Re: MSX2 Compatible Computer Project [message #6846 is a reply to message #6845] Thu, 28 November 2019 08:59 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 212
Registered: October 2015
Location: Portland, OR
Senior Member
Doug,

Thanks again.
That document is kind of work in progress. It is very likely it will contain a lot of errors. I removed that reference to 8087 and some other non-relevant stuff. I need to find time to edit in the actually relevant content.

- SK
Re: MSX2 Compatible Computer Project [message #6849 is a reply to message #6846] Mon, 02 December 2019 02:41 Go to previous messageGo to next message
jordi.solis is currently offline  jordi.solis
Messages: 88
Registered: March 2017
Member
Hi guys,
I have some Obsonet 1.0 bare boards available, this will let you build an MSX network card with developed drivers for MSX-DOS and NEXTOR.
you can see all the projetct details here:
http://obsonet.blogspot.com/
If you like I can send you one board at 5$ + shipment.
Let me know
Jordi Solis
Re: MSX2 Compatible Computer Project [message #6856 is a reply to message #6849] Wed, 04 December 2019 11:08 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 212
Registered: October 2015
Location: Portland, OR
Senior Member
Speaking about MSX hardware expansion, Xavirompe was kind enough to send me his Rookie Drive NX. I've tested it with Omega and it works perfectly Smile
I guess that resolves "we need an FDC interface" issue ;-)

- SK

/forum/index.php?t=getfile&id=1582&private=0
Re: MSX2 Compatible Computer Project [message #6857 is a reply to message #6856] Wed, 04 December 2019 14:12 Go to previous messageGo to previous message
jordi.solis is currently offline  jordi.solis
Messages: 88
Registered: March 2017
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hi Sergey, all
I saw that U15-18 are 74HC on the bom but 74HCT on the silkscreen. So I looked for its differences on the internet.
It seems like they are equivalents, but even better 74HCT are level compatible with 74LS.
I'm getting hard to find some of them specially AHCT, so... Could I just mix hct with LS or replace the AHCT by 74F or 74ALS?
I don't think you were specified most of them as HCT but some as 74F if that wasn't a matter.

Just consider include this (HC vs HCT) as an issue.
J. S.
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