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387sx-33 in 386sx-40 system?

stamasd

Member
Joined
Apr 28, 2014
Messages
12
Location
greater NYC area
I have a 386sx-40 board to which I want to add a coprocessor. The chip I have is this exact one:

L_ULSI-MathCoSX-33.jpg


The board is the same as this one, a M396F with Am386sx-40:

m396f.jpg


Will it work?
 
Will it work? Most likely it will work well enough for you to boot and run the system. The coprocessor may have problems with certain functions while running at 40MHz; only using testing software can determine how good the specific processor is. If 9349 translates to the production date, then I expect most 387 and 387sx production would be capable of 40MHz with many chips being labeled as slower to fill the market for cheaper chips.

http://wiretap.area.com/Gopher/Library/Techdoc/Cpu/coproc.txt mentions some issues regarding overclocking and suggests some tests. Also has some interesting commentary about the ULSI brand coprocessor.
 
Will it work? Most likely it will work well enough for you to boot and run the system. The coprocessor may have problems with certain functions while running at 40MHz; only using testing software can determine how good the specific processor is. If 9349 translates to the production date, then I expect most 387 and 387sx production would be capable of 40MHz with many chips being labeled as slower to fill the market for cheaper chips.

http://wiretap.area.com/Gopher/Library/Techdoc/Cpu/coproc.txt mentions some issues regarding overclocking and suggests some tests. Also has some interesting commentary about the ULSI brand coprocessor.

Thank you! This is exactly the type of document I was looking for. The manufacture date of my particulsr chip is 9344, i.e. 5 weeks apart from the one in the picture. If I have no trouble booting the sydtem I will try some of the benchmarks, assuming I can find the programs.

If I were to try this, I'd keep a heatsink on the coprocessor, just to be safe.

Will do.
 
Funny I have this same board. LOL. It doesn't support asynchronus CPU-FPU speed, so you are stuck with either running the FPU at 40 MHz and hope it is stable (maybe even use PRIME95 to find out, if you can), or underclock the CPU at 33 MHz. I don't expect that you will run into any cooling issues with the FPU at 40MHz. It will only draw 20% more power and all the FPUs I've seen barely get any temperature you can feel with your finger.

do something about that leaking battery.

+1
 
I think the FPU is the least of your concerns. For the love of god please do something about that leaking battery.

That is not a picture of my actual board but a stock photo. I have long removed the battery from mine and replaced it with an external alkaline battery box from Radio Shack.

Funny I have this same board. LOL. It doesn't support asynchronus CPU-FPU speed, so you are stuck with either running the FPU at 40 MHz and hope it is stable (maybe even use PRIME95 to find out, if you can), or underclock the CPU at 33 MHz. I don't expect that you will run into any cooling issues with the FPU at 40MHz. It will only draw 20% more power and all the FPUs I've seen barely get any temperature you can feel with your finger.



+1

Correct, the FPU doesn't even get warm during normal operations. I have yet to submit it to some stress testing. But it doesn't seem to impede normal operation of the system at all at 40MHz.
 
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