adding 4mb SGRAM to PowerPC 5500/6500 ... and possible ATi Rage Pro upgrade

[sheytan]

@pizzigri, did this ever go anywhere? Sounds like an exciting path for TAMs!

 

[croissantking]

So, Jeff graciously sent me a few KM4132G512Q-10 chips, they're 256 X 32 X 2 (2MB) each, while the chips already soldered on the 6500 are MT41LC256K32D4, 128 X 32 X 2 (1MB). I am adding both Data Sheets below.
While the pin for BA, according to the 6500 schematic, is connected (they are both dual bank chips) the caveat here is that address lines A8 and A9 are, for some unfathomable reason, mapped on different pins on the MT and KM memory chips footprint which are otherwise essentially the same.
I will undoubtedly have to bodge some wires to solve this.

I was just looking at the datasheet for the km4132g512q and it needs 10 address lines (notice that pin 29 is now a10 rather than a9) whereas the Rage Pro only has 9 address lines according to the Gossamer and Columbus schematics.
Piggy-backing chips (not easy with QFP - I tried) is the only way to do this.

 

[Phipli]

It's a real pain that apple didn't do the standard arrangement of two chips with a socket for a module on top. That would have given us the same flexibility as the G3 with up to 6MB.