Creative Microsystems STPA05 booster

[coonsgm]

Greetings all,

I came into possession of a 520ST with a vintage CMI / Creative Microsystems STPA05 accelerator card installed. It's a nifty card that has a 16mhz 68k, a Blitter socket (populated with a functioning blitter), an FPU, fast ROM sockets, and an "expansion bus".

Running gembench it scores equivalent to a Mega STe @ 16mhz....so it's been fun to play around with.

I've been trying to find documentation on this card and have only found an article https://www.atarimagazines.com/startv4n5/speed.html

I was hoping someone here might know where to find some documentation on what's needed to get the FPU functional / recognized. So far I've been unable to get the FPU recognized by either Sysinfo / Gembench and I'm trying to figure this out....

Thanks!

[rubber_jonnie]

Picture in the motherboards images section please :)

[coonsgm]

Ok ok 😁. I’ll take some photos. I’m posting YT video on it later today as well.

[coonsgm]

IMG_0772.jpg

IMG_0773.jpg

[Steve]

Nice little accelerator, quite full featured! I assume those two empty sockets would be for TOS ROMs.

[tOriman]

Hi!

@coonsgm

Look at U12 chip near FPU - it is 74F74 dual D Flip-Flop. It seems very strange soldered this way...

Nice device, quite big :) Many fixes

tOri

[coonsgm]

Look at U12 chip near FPU - it is 74F74 dual D Flip-Flop. It seems very strange soldered this way...

I know the other logic chips have additional weirdness as well. That said, CMI also made accelerators for Amiga's and they also had similar odd usage of logic chips.

[rubber_jonnie]

I'm guessing for that for U12 they didn't need all of it, or it was replacing another similar chip with slightly different pinouts. Looks like it's trying to climb out and run away :)

Also wondering why there is a snipped black wire on the CPU? As for bodge wires, seems like a few were needed, and I'm wondering how many are factory, and how many are aftermarket?

The 'EXPANSION' header is also quite interesting.

Thanks for the pics.