I'm
trying to track down a 387 math coprocessor IC for an old
386-based
Linux box that's going to be doing a bit of
numbercrunching for me. Has
anyone here got an AMD or Intel (AMD preferred) 387 coprocessor rated at
40MHz (-40 part number suffix) that would work correctly with an AMD
Am386DX-40? No, before you ask, the 386DX does *not* have a built in
mathco - the 486DX was (IIRC) the first DX-series chip with a built-in
coprocessor.
They come up on epay all the time, pick yer flavor. I just got a 40MHz
Cyrix Fasmath chip for $2 (includes $1 shipping) a week ago. Supposedly
clock for clock it's the fastest of the '387 FPUs, but IDK. Popped right in
to to my P70.
It was a tiny bit faster than the AMD and Intel parts depending upon instruction
mix.
I'm still looking for a set of eight 2MB 72 pin
IBM SIMMs with presence
detect, and a Cyrix 486Drx2, which is a 486 with a '386 pinout, if anyone
has a spare.
It's not quite a 486. It actually is a double clocked 386 with a small
internal L1 cache. It doesn't share most of the instructions unique to the 486.
I don't currently have a DRX2, but I do have a DRX, which is essentially the
same thing without the clock doubled core. The L1 cache made it about 20%
faster than an equivalently clocked 386. You had to explicitly turn on the
cache, and set regions as uncachable. (Caching the video card usually made
for problems.)
Eric