Subject: MSX2 Compatible Computer Project Posted by Sergey on Tue
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Subject: MSX2 Compatible Computer Project Posted by Sergey on Tue, 23 Jan 2018 21:12:41 GMT View Forum Message <> Reply to Message 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?): 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 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 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 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 Subject: Re: MSX2 Compatible Computer Project Posted by danwerner on Tue, 23 Jan 2018 22:55:21 GMT View Forum Message <> Reply to Message Page 1 of 148 ---- Generated from RetroBrew Computers Forum 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 Subject: Re: MSX2 Compatible Computer Project Posted by mscane on Wed, 24 Jan 2018 00:39:17 GMT View Forum Message <> Reply to Message 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 :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). 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 Page 2 of 148 ---- Generated from RetroBrew Computers Forum Subject: Re: MSX2 Compatible Computer Project Posted by danwerner on Wed, 24 Jan 2018 00:43:06 GMT View Forum Message <> Reply to Message 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 Subject: Re: MSX2 Compatible Computer Project Posted by lynchaj on Wed, 24 Jan 2018 01:16:40 GMT View Forum Message <> Reply to Message 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! Subject: Re: MSX2 Compatible Computer Project Posted by Sergey on Wed, 24 Jan 2018 01:33:08 GMT View Forum Message <> Reply to Message Thank you for your feedback guys! danwerner wrote on Tue, 23 January 2018 14:55You 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 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 16:39Hi 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 Page 3 of 148 ---- Generated from RetroBrew Computers Forum 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 17:16I 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. Subject: Re: MSX2 Compatible Computer Project Posted by lynchaj on Wed, 24 Jan 2018 11:28:29 GMT View Forum Message <> Reply to Message 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. Subject: Re: MSX2 Compatible Computer Project Posted by lynchaj on Sat, 10 Feb 2018 16:43:22 GMT View Forum Message <> Reply to Message Any updates? Page 4 of 148 ---- Generated from RetroBrew Computers Forum Subject: Re: MSX2 Compatible Computer Project Posted by Sergey on Sun, 11 Feb 2018 17:16:31 GMT View Forum Message <> Reply to Message 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 Subject: Re: MSX2 Compatible Computer Project Posted by jordi.solis on Thu, 22 Feb 2018 17:18:38 GMT View Forum Message <> Reply to Message Hi, I would like to help to help on this project.