Thursday, 13 November 2014

Back in a flash!

Copping a lot of heat to get the Neo Geo flash cartridge finished off. To be honest, I'm feeling burnt out at work and the knock-on effect is that I don't feel motivated to do any computer-related activities in my own time either - even fun stuff like Neo Geo. So I find myself riding my bike and surfing the net...

However I'm making a concerted effort to get the grey matter ticking over and move things along now, particularly in light of the fact that come Jan 27th 2015 - or thereabouts - I'll have a lot less time for leisurely pursuits with the arrival of a little boy.

To this end, I decided to look at cartridge capacities and try to work out what size flash devices I'd need on a programmable flash cartridge. Keeping in mind that the prototype need only be large enough for a single game, I'd like the option for that to be ideally any game currently available for the Neo Geo! For the purposes of this exercise, I chose to use The King Of Fighters 2003 as a benchmark.

The numbers I ended up with (KOF2003 bracketed) are:
  • P-ROM (9MB) = 16MB/128Mb (x16)
  • C-ROM (64MB) = 64MB/512Mb (x32)
  • V-ROM (16MB) = 16MB/128Mb (TBA)
  • S-ROM (none) = 512KB/4Mb (x8)
  • M-ROM (512KB) = 512KB/4Mb (x8)
These are reasonable numbers for single/dual device solutions per bus, and flash is surprisingly cheap, so no big deal here. I could probably even double it if I felt the need. As it stands though, the proposed flash cartridge will therefore have a capacity of 776 MBits.

I want to get a preliminary design of the flash cartridge drafted before I commit the programmer/analyzer PCB to manufacture. However I need to do some more research on the bank switching and protection on the various carts before this task is complete. Either that or throw a large CPLD into the mix, and pass most of the address lines through it...

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