Yah!

This morning I managed to get the OCM booting on my hardware. It was a useful exercise because a learnt a few things about Quartus and serial configuration devices which I didn't know a few days ago.

I've got some experimenting and some cleaning up to do, but I'll post some more detailed information and a "how to" on my website in a few days. In a nutshell, unless you're porting to a platform with a Cyclone(/II), an EPCS4(/8/16??) and some SDRAM, then you're SOL...

Some eye-candy...
<members.iinet.net.au/~msmcdoug/pace/platforms/pace-p2/ocm.jpg>

(The picture's a little dark... didn't look that dark on my PC at home...)

Regards,
Mark

Very cool Mark Will be interesting to read the how to when you have it ready

Quote:

(The picture's a little dark... didn't look that dark on my PC at home...)

I artificially enhanced the picture contrast. Here it is:

http://eggerland.googlepages.com/ocmalt.jpg

Feel free to take a copy.

Hahaha, pretty cool

Very very interesting.
Are you using a standard Altera or Xilinx developmentboard?

No, not a standard board. It's proprietary hardware, for which I designed an add-on board with video and PS/2 input.
But basically any (Altera) platform with the features I mentioned in my OP will do.

What is the lowest price of the simplest board with SD,PS/2,sound and any modern video connector on it, on which the clone can be implemented ?

I've put together a few quick notes on how the OCM works and what is required to port it to another platform.
<members.iinet.net.au/~msmcdoug/pace/platforms/ocm_howto.txt>, or
<members.iinet.net.au/~msmcdoug/pace/platforms/ocm_howto.htm>

Note that it's not a comprehensive tutorial for VHDL newbies. You will need some experience with Altera devices to get it working. Having said that, I'm happy to answer any OCM-specific questions if you're attempting a port.

Would like to hear from anyone that manages to get it going on another platform!

Regards,
Mark

Amazing !!!

Do you have any sound output on your board ?

I just found the following dev board that can be bought for 99$ (not including shipping). They say it has headers to which you can connect various extentions, available from 3rd parties. I think this means SD-drive can be connected as well.

Is it possible to port OCM to it ?

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I just found the following dev board that can be bought for 99$ (not including shipping). They say it has headers to which you can connect various extentions, available from 3rd parties. I think this means SD-drive can be connected as well. Is it possible to port OCM to it ?

Theoretically it seems possible, but there are some essential components missing, like SD-RAM. It has 1MB SRAM however, so with a smaller mapper and a lot of effort it can work. Also I can't find a flash component.

A better choice would be:

http://www.altera.com/products/devkits/altera/kit-cyc2-2C20N.html


It has everything required, including VGA, SD/MMC card slot, SD-RAM (only 8MB, but should be okay), EPCS4, bigger CycloneII FPGA, USB-Blaster download cable on-board.... And it only costs $150.-

The only thing missing compared to the real OCM is the MSX card slot and the beautifull casing.

For those who have no cartridges and do not mind a missing casing, it seems even a better solution as it has more gates...

Yeah, I'm not sure how much SDRAM the design requires in all.

Note that the EPCS4 might be too small to store both the ROMs and the Cyclone-II image (haven't tried compressing a 2C20 .SOF).

Cax - my current board does have a simple (audio) RC filter designed for an on-chip sigma-delta DAC, but I'm yet to load the parts. The next incarnation of my adapter board (you can see the adapter board in the photo) will have a proper audio DAC and amplification. Incidentally it will also have a JAMMA connector so in theory I could play MSX games in my cabinet with 26" display and arcade joystick controls!

I'll also have to attempt to load a cartridge image into the SRAM of my board and see if I can get it running...

I think with a bit of time it should be possible to completely understand the IPL ROM and provide alternate versions for loading the ROMs from elsewhere other than the EPCS configuration device. Parallel flash (or even SRAM) would be a good start.

From what I can tell, the same module (megasd.vhd) controls both the EPCS device and the MMC/SD device. This would make sense because AFAIK the EPCS device is a SPI device, and MMC/SD also has a SPI mode. Perhaps it is already possible to boot the MSX ROMs from a properly-formatted SD/MMC card??? I have absolutely no experience with these devices so I'm only guessing atm...

As for using SRAM vs SDRAM - it should be possible without too much effort to modify the design to use SRAM. As I said earlier, I have no idea how much RAM is required to make this thing run. Obviously the SDRAM refresh logic can be ignored/eliminated. The only other complication I can think of is that the logical address is time-multiplexed on the SDRAM physical address bus. But that shouldn't be too difficult to handle. I haven't looked at the memory bus state logic so I'm not sure what speed SRAM you can get away with.

Food for thought....

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As for using SRAM vs SDRAM - it should be possible without too much effort to modify the design to use SRAM. As I said earlier, I have no idea how much RAM is required to make this thing run. Obviously the SDRAM refresh logic can be ignored/eliminated. The only other complication I can think of is that the logical address is time-multiplexed on the SDRAM physical address bus. But that shouldn't be too difficult to handle. I haven't looked at the memory bus state logic so I'm not sure what speed SRAM you can get away with. Food for thought....

This should indeed not be too complex. The first prototype of OCM actually did have SRAM and not SDRAM. In a next prototype it got replaced with SDRAM to save costs. However, as far as I know, the changes in the VHDL code where kept to a minimum for this switch. So it should be relatively easy to switch back again.