386SX math processor \ VOGONS

386SX math processor

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First post, by doublebuffer

Posted on 2023-06-23, 12:06

doublebuffer Offline

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Hello all,

I am a bit confused about 386SX and corresponding math processor compatibility. Do they need to be same frequency or does 387SX work with all 386SX processors? Since these are somewhat rare, I have one offer for A80387-25 SX106* but I am not sure whether it works with my 386SX which is only 16 mhz. If anyone knows, I'd appreciate any tips before buying one.

* https://www.cpu-world.com/sspec/SX/SX106.html

Reply 1 of 2, by Disruptor

Posted on 2023-06-23, 12:20

Disruptor Offline

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CPU and FPU don't need to have the same frequency rating.
You just have to ensure that nothing is overclocked.
As in your example, when your CPU is clocked lower than the FPU is rated, you won't face any problems except than the FPU won't show the performance it was built for.

But: You have linked a FPU with Intel S-Spec number SX106. This FPU is a 387 DX with a 32 bit interface. It won't run with a 386 SX CPU which has a 16 bit interface.

Last edited by Disruptor on 2023-06-24, 15:36. Edited 1 time in total.

Reply 2 of 2, by doublebuffer

Posted on 2023-06-23, 12:30

doublebuffer Offline

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Disruptor wrote on 2023-06-23, 12:20:

But: You have linked a FPU with Intel S-Spec number SX106. This CPU is a 387 DX with a 32 bit interface. It won't run with a 386 SX which has a 16 bit interface.

Thanks, you saved me. The part number had SX in it so I assumed it would be SX not DX, I need to try to find an another one then. Really helpful, thank you again!

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