Perhaps for 386 boards without socket for a 387 math coprosessor.

This has been listed a long time. Asked the seller about a year back to maybe show me the underside of the board by way of picture / written description and they were not very helpful unfortunately. It made me wonder if they actually wanted to make a sale or not.

Anyways, i'm pretty sure it is an older adapter for 386 motherboards that do not have a 387 socket. I'm pretty sure there will be PGA132 male socket on the underside, but until the seller becomes a little more buyer friendly / helpful... We will never know.

Here's to helpful and friendly sellers!

Probably a 387 upgrade board for system without a socket for the 387
Or a laptop cpu.

Also somewhat relevant
http://www.minuszerodegrees.net/images4/HYPER386-SX.jpg
http://www.cpu-world.com/CPUs/80386/Intel-Sna … 80386SX-20.html

There was an adapter on eBay that was a 286 to 386 adapter, and it looked VERY similar to this. The underside of the board revealed that there were pins under the main processor, which was a 386 sx in this case, that plugged into a 286 socket.

You notice the board is raised significantly on the side with the main 386 processor on the board above. I imagine this was a similar idea. Perhaps a dickered 386 sx board which utilized this adapter to become DX?

If I had to take an educated guess it looks like it was meant as an upgrade for a very early 386DX motherboard which had a socket for a 287 coprocessor since the 387 was late. A 386DX16 is the earliest 386 you will find. Micronics was huge in high end motherboards back in the day.

https://en.wikipedia.org/wiki/Intel_80386

"The i387 math coprocessor was not ready in time for the introduction of the 80386, and so many of the early 80386 motherboards instead provided a socket and hardware logic to make use of an 80287. In this configuration the FPU would operate asynchronously to the CPU, usually with a clock rate of 10 MHz. The original Compaq Deskpro 386 is an example of such design. However, this was an annoyance to those who depended on floating point performance, as the performance advantages of the 80387 over the 80287 were significant."

Guys...

We still trying to figure this one out...

It has "387 ADAPTER REV. D" silk-screened on it!