OK Mr. Junkie,
I think we have a misunderstanding. Of course we both can count, I don't really doubt it 😵
In my original post I said there is no "standard drop in replacement" for socket PGA132 which is faster than the SXL2-50. What I really wanted to say is that there is no native CPU above the SXL2-50 in this CPU line. Of course there are socket PGA168 CPUs on a converter for the PGA132 socket, and the nice SXL2-66 you showed in the thread, but I wouldn't call then native PGA132 CPUs. I hope this claifies what I intended to say. I think my term "standard drop in replacement" was a bit misleading.

Cheers,
Fabian

It really just depends on what you want to include in your definition. This doesn't really seem like a point worth debating. If including interposers, there is also the IBM Blue Lightning BL3, which is faster than the SXL2-66. The fastest PGA-132 CPU without an interposer is either the Cyrix DRx2-66 or the TI SXL2-50.

When I read the OP title, I interpret this as why are there no PGA-168 to PGA-132 adapters to allow for use of any PGA-168 CPU on PGA-132 motherboard. For this case, there is the Transcomputer module, which seems to work pretty well.

I think that's really depending on the each person's point of view.
Some chips left the factory with interposers, some got them aftwerwards.
Same with mainboards/chipsets. Some were pure (386 or 486), some were hybrids (386+486)..

386SX wrote:

did a socket adapter ever exist to put a 486 maybe the lower models onto a 386 socket?

It seems now that it did...

I hope to reverse engineer and create a copy from this one... maybe even make a socket version... rather than QFP.

What the heck is this? Why would anyone want to use a 386 CPU on a 486 motherboard? Very fascinating find. Did you try this in a socket 3 motherboard?

That might make sense with respect to the slowest 486 cpus, like 486sx16 and 486sx25.

386_junkie wrote:

I hope to reverse engineer and create a copy from this one... maybe even make a socket version... rather than QFP.

Have you tested this to work? It is very interesting indeed. It seems to be a relatively simple device. But what is the deal with the two extra rows of contacts within the socket 3 pins? Was another chip supposed to be placed there?
Hope you can share the wire routing diagram at some point.

gerwin wrote:

386_junkie wrote:

I hope to reverse engineer and create a copy from this one... maybe even make a socket version... rather than QFP.

Have you tested this to work? It is very interesting indeed. It seems to be a relatively simple device. But what is the deal with the two extra rows of contacts within the socket 3 pins? Was another chip supposed to be placed there?
Hope you can share the wire routing diagram at some point.

Have created a separate thread which will get updated as I go, there you will find progress so far: -

486 to 386 CPU module

Sure, any work I do on it will be freely available to all.

feipoa wrote:

Why would anyone want to use a 386 CPU on a 486 motherboard?

Let me retort... what technology is available to a 486,.. that is not to a 386?

...

I'm thinking along the lines of... PCI bus, 3D cards, chipsets etc... but I guess that would only be the beginning, it opens a door.

As I stated in the other thread, this was likely an adapter for certain hybrid 386/486 boards. I really doubt it would work on a PCI motherboard.