I don't think you can use that FPU.
The CPU runs at 33 MHz, and Cyrix 387 FPUs don't support asynchronous.
And those Reveal parts seem to be rated up to 25 MHz:

The above seems to jive with what I am reading at How to run your FPU asynchronously on 386 motherboards

Only Intel branded co-processors support that Async jumper. It is possible I believe that the co-processor may run overclocked to match the CPU speed?

I believe there are diagnostic disks that will determine if the math co-processor is functioning for example: https://downloads.avaya.com/elmodocs2/intuity … udia3.htm#16787

Well, that’s not good. Anyone know where I can find a 40mhz math co-processor for this motherboard ?

I can't really help you other than telling you to "just try", however I have added your photo here http://www.win3x.org/uh19/motherboard/show/3845

Also, I have run a 20Mhz cyrix FPU in a 25Mhz system and even a 33Mhz one iirc and it worked.

If you figure it out I can add that info as well (And there are some more things that you can do if you want to help us with that one like bios upload, chipset id ...)

Intel486dx33 wrote on 2020-08-31, 17:53:

Well, that’s not good. Anyone know where I can find a 40mhz math co-processor for this motherboard ?

Your CPU seems to be a 40 MHz one, but your OSC1 is 66 MHz - so the CPU runs at 33 MHz, and a 33 MHz FPU would be enough.
Also, you can get an Intel FPU, and run it asynchronously - of course, you would also need an appropriate crystal for OSC2.

Currently the CPU runs at 33mhz. I have not switched the jumpers to see it it will run at 40mhz.

Will this one work ?

Intel486dx33 wrote on 2020-08-31, 17:53:

Well, that’s not good. Anyone know where I can find a 40mhz math co-processor for this motherboard ?

If you register at http://www.cpu-world.com/forum/ various different 387 turn up frequently in the For Sale forum. You could also post in the Wanted section. Prices are usually among the best you will find.

The Intel 387 you posted above would do the job.

That Reveal FPU has a datecode of 35th week of 1993. Cyrix had already perfected their FPUs by that time. In 1993 they were moving tonnes of 40MHz FPUs paired with the DLC chips. Their 83S87 used the same core as their 83D87, so I would guess you have a good shot at 33MHz and even 40.

BTW, that Reveal kit probably sold for a couple of years, and they likely would have updated the packaging and the contents along the way. That box didn't come with your FPU, so it doesn't exactly tell the whole story.

But not so much on-topic, I would get that battery of the way very soon ..