I have an old 386 computer with an intel 80386-DX in it. Little did I know, it's not soldered to the board as many are, but plugged into a socket so I can swap it out. I was thinking of putting an AM386DX-40 in instead. My motherboard is a MB1333C/40-CH. It also has a coprocessor socket and says it takes both Weitek and 387 chips.
Here's the thing... several things confuse me about how to combine chips.
Every 387 I've ever seen has only 2 rows of pins (what do they call it, PGA 68 pin?) but the socket has a PGA 132, which is 3 rows of pins... BUT it says 80387 right on the board! Does a 68 pin coprocessor fit in a 132 pin socket?
Can't seem to find a 387 at 40 MHz for sale. Will the coprocessor run asynchronously with the CPU? Can I put an 80387DX-33 in there with the AM386DX-40?
Here's the 1 picture on the internet I could find of my motherboard:
That's not as old as some so it can't be called "antique". They aren't making the original chips anymore so you will have to find the part in a recycling facility. I don't think the AMD and Intel parts were pin-compatible, so you might have to find the datasheets to make sure.
This forum is "bar sport" so here is an approach that might be easier. Get a plug that fits into the socket and mount an Arduino on it. Put in some level shift chips and build a "Frankenstein-duino" computer in the original case. You get extra points if your sketch can use the floppy drive.
Somehow I feel you missed the point of the thread... I'm not trying to rig up some arduino project. I'm trying to understand the pin compatibility of 386 and 387 processors with each other and with their respective sockets. And Intel and AMD 386s are pin compatible, as AMD made direct fit replacements for the 386. It's not a brand issue but a package issue because these chips came in different packages and mated to different sockets.
If my memory's correct there is no problem with cpu and coprocessor at different frequency.
I had my suspicions that that was true as well. That's one good piece of news. Now if only I could figure out the pin and socket problem... way more sockets than pins on any 387 I've seen. Must be overlap between the 2 patterns so both will fit.
Apparently the Weitek coprocessor is in a 121pin PGA. http://www.cpu-world.com/CPUs/3167/index.html
(that's what's shown in the picture you linked (613 + 76 + 1) - you must've miscounted.)
Haha... admittedly I did not count the pins but it's about that yeah. I came across the Weitek but didn't occur to me they'd make the socket able to fit both. I guess both are pin compatible with the socket then. That Weitek seems to be described as having a vastly different architecture but being overall inferior (by virtue of its limited support and application). Still, if my 387 doesn't fit at least I have another option.