Have been making my own bootlegs for fun and (no) profit and realised that the lack of a pin-compatible 64mbit (8 meg) EPROM for C ROMS is a limiting factor for some of the larger games. Also the lack of a 8-bit addressing 32mbit (4 meg) EPROM for V ROMS is a bit of a pain, requiring them to be split onto 2 x 160's.
A lot of the Chinese bootlegs just bodge 3.3v chips straight onto the board with 5v signalling which works great until it stops working.
Luckily the awesome Tdaede considered this problem a long time ago and solved it with this adapter. Takes super-cheap 3.3v flash, adjusts the voltage, translates the addresses, its a technical work of genius.
https://github.com/tdaede/toshiba-64mbit-adapter
Before starting; the smart thing to do is waste several days drawing custom graphics (and redrawing existing graphics) so that we can make the boards look cool. Initially I was going to use Inkscape for this to test out the new Vector Graphics import functions in Kicad 8. but then I didn't. Importing custom Bitmap graphics into Kicad 8 is also less painful than it was in 6/7 (Image converter -> Save to file -> Footprint editor -> import -> save to library -> board editor -> place -> footprint). I'm guessing things like fully automatic trace routing are higher on the feature list that easy custom graphics, so time spent learning the current workflow is not going to be wasted.
The PCB editor of Kicad8 has some cool new features - one that I particularly like is "snap to" in the edge cuts layer even when holding control, makes it much easier to cut a notch out of the top of the board like the one here.
The 3D board viewer in Kicad 8 has had some great enhancements too - change the colour of the board or the silkscreen or the mask or whatever just by clicking on the coloured box in the appearance manager. Previously this functionality was buried deep in "preferences". Here they are in NeoGeo Red and White
So now that they look cooler, which is half the battle.
A lot of the Chinese bootlegs just bodge 3.3v chips straight onto the board with 5v signalling which works great until it stops working.
Luckily the awesome Tdaede considered this problem a long time ago and solved it with this adapter. Takes super-cheap 3.3v flash, adjusts the voltage, translates the addresses, its a technical work of genius.
https://github.com/tdaede/toshiba-64mbit-adapter
Before starting; the smart thing to do is waste several days drawing custom graphics (and redrawing existing graphics) so that we can make the boards look cool. Initially I was going to use Inkscape for this to test out the new Vector Graphics import functions in Kicad 8. but then I didn't. Importing custom Bitmap graphics into Kicad 8 is also less painful than it was in 6/7 (Image converter -> Save to file -> Footprint editor -> import -> save to library -> board editor -> place -> footprint). I'm guessing things like fully automatic trace routing are higher on the feature list that easy custom graphics, so time spent learning the current workflow is not going to be wasted.
The PCB editor of Kicad8 has some cool new features - one that I particularly like is "snap to" in the edge cuts layer even when holding control, makes it much easier to cut a notch out of the top of the board like the one here.
The 3D board viewer in Kicad 8 has had some great enhancements too - change the colour of the board or the silkscreen or the mask or whatever just by clicking on the coloured box in the appearance manager. Previously this functionality was buried deep in "preferences". Here they are in NeoGeo Red and White
So now that they look cooler, which is half the battle.
