YAY! I am glad that it will be brought to the Replay board but what I am interested in is making separate Data, Address and I/O chips sets that would plug directly in the actual mother boards. I would imagine myself and other Astrocade home system and arcade system owners would be more than happy to be able to resurrect some dead boards( due to failed custom chips) Is it feasible to to use something smaller like a CPLD and program it to act like the original pin for pin? These customs are 40 pins btw. I do realize that these chips are usually 3 volts and probably would require some voltage regulation from the 5 volts on the Astrocade boards but I am sure they already exist. Keep in mind, there are plenty of us 'purists' out here ( whatever the heck that actually means 
) who would like to keep our old hardware up and running.
I was actually looking at how you did some of the Address chip code and that you kludge( or what little I know about HDL code) this by moving the four RAS line down to one. That would probably need to be expanded out to use the actual 4 lines if replacement chips were to be made plugin ready for the existing boards.
If you were not already aware of how the address chip accesses memory for its 3 gfx modes, I was told by Bob Ogdon who was on the Nutting design team, that the way the Astrocade works in lo res mode, 160x102, is it requires only one bank of 4k by 8 bits using RAS0 as it's row address scan, but in the medium( yes this is a mode if you did not already know this which I do not believe any game ever used) res mode(160x204), it requires 2 banks and they have to be set up as 2 banks of 4k x 8 bits, which looks like 16 bits or 2 totally separate 8 bit paths to the address chip, RAS0 for bank 0 and RAS1 for bank 1. Then in the final mode, the hires 320 x 204 mode, you need all four RAS lines which are 4k banks of 8 bits each and according to Bob, these look like 32 bits or 4 totally separate paths of 8 bits each to the address and data chip.
I only tell you this as the 'kludge' you used in your code( not that I fully understand what you did there btw) tells me you may not have been fully aware of how this operates. I was blown away when I ran that on my Xilinx Spartan 3E, BTW...AWSOME!.
Could you give me a link to these 42 pin boards? I'd like to take a look at those. How expensive could they be?
Thanks for any help you can supply. It is well appreciated as I know you are very busy.
