I think that Socket 4 motherboards are quite rare these days. Try searching for "Pentium 60" or "Pentium 66" (with or without "motherboard" at the end).
I found one result with a Pentium 60 MHz included but, the seller wants EUR 199...

Yeah when I do find one prices are crazy! I’d love to get a hold of one someday but it’s tuff to justify the prices.

Sometimes you get lucky. Just keep on searching (locally and abroad)

Maybe its worth trying to find an OEM system form Compaq, Dell, HP, Digital etc? Some of them used separate CPU cards such as the Compaq Deskpro XL series. I just buyed an Deskpro XL 575 that has a Pentium75 CPU card, but i will put an Pentium Pro 200 card in that.
I see one seller has a Pentium 66 CPU card for sale to a Deskpro XL. Its temting to buy that but im covered with my four Pentium 66 CPU cards for my Compaq Proliant 4000 server.

Your best bet is going to be to find somebody with a complete setup, working or broken IMO. Socket 4 was never really ubiquitous, especially for home builder/consumer boards, but you can find one if you just keep looking... Even socket 5 is tough to find for a reasonable price 😢

One has to be lucky and on the lookout like a little squirrel.
Came across my first, and yet best board, by pure luck but still dished out a €100(+CPU)... and to be honest, it was worth every penny - well kept and a sight to behold.

Scraphoarders OEM tip seems like a good option to shelve some proper hardware as all the user boards seem to be entering stratospheric prices due to perceived rarity.
From where are you fsmith - in Germany there's one to be had for €149 which has cpu, ram and an onboard CirrusLogic card.

Forgot... found mine by search criteria "Pentium SX", albeit this may not be the best one on ebay.

amadeus777999 wrote:

One has to be lucky and on the lookout like a little squirrel. Came across my first, and yet best board, by pure luck but still […]
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One has to be lucky and on the lookout like a little squirrel.
Came across my first, and yet best board, by pure luck but still dished out a €100(+CPU)... and to be honest, it was worth every penny - well kept and a sight to behold.

Scraphoarders OEM tip seems like a good option to shelve some proper hardware as all the user boards seem to be entering stratospheric prices due to perceived rarity.
From where are you fsmith - in Germany there's one to be had for €149 which has cpu, ram and an onboard CirrusLogic card.

Forgot... found mine by search criteria "Pentium SX", albeit this may not be the best one on ebay.

I am from Illinois, USA. I will check that out, thanks!

Also, is there a good source to see which OEM's came out with a socket 4 machine? I know of Packard Bell and Compaq for sure but not sure who else?

And one more thing, I am not familiar with those CPU add-on boards like the Compaq Deskpro XL's How exactly do those work?

Is it allowed to post a link here - the P60/Cirrus board is on ebay/kleinanzeigen...

fsmith2003 wrote:

And one more thing, I am not familiar with those CPU add-on boards like the Compaq Deskpro XL's How exactly do those work?

CPU cards come in many types, but for the Deskpro XL its a card with the CPU socket and also onboard ram + extra ram sockets. Its plugged in a prorietary slot on the motherboard. This design allowed upgrade options, but with every vedor taking their own route you was locked in.

The Deskpro M 5/60 seems to use the same CPU card as the XL, but with a different bracket. Another model was the Deskpro XE with the CPU socket and ram on the motherboard, but that had a riser card for the ISA or EISA slots. Partnumber for Deskpro XE 560 MB is 142838-001.
The problem is you have to get a riser card and a case. It has a standard AT PSU connector so you could probably use it without a Compaq case.

Scraphoarder wrote:

CPU cards come in many types, but for the Deskpro XL its a card with the CPU socket and also onboard ram + extra ram sockets. It […]
Show full quote

fsmith2003 wrote:

And one more thing, I am not familiar with those CPU add-on boards like the Compaq Deskpro XL's How exactly do those work?

CPU cards come in many types, but for the Deskpro XL its a card with the CPU socket and also onboard ram + extra ram sockets. Its plugged in a prorietary slot on the motherboard. This design allowed upgrade options, but with every vedor taking their own route you was locked in.

The Deskpro M 5/60 seems to use the same CPU card as the XL, but with a different bracket. Another model was the Deskpro XE with the CPU socket and ram on the motherboard, but that had a riser card for the ISA or EISA slots. Partnumber for Deskpro XE 560 MB is 142838-001.
The problem is you have to get a riser card and a case. It has a standard AT PSU connector so you could probably use it without a Compaq case.

So these are unique to the motherboard they were designed to work with then it sounds like? They wouldn't work on another motherboard type or brand?

I may have jumped the gun but I put a bid in on a Compaq Deskpro XE 560 motherboard but it did not have the riser card. Where would I find which type of riser card I should be looking for at this point?

Just search for Pentium and weed them out by speed. Packard bell sold a ton of P60 machines so you can look for that brand, same with Gateway. Not that many 3rd party Socket 4 boards out there since they kind of came and went to fast (and were expensive).

fsmith2003 wrote:

I may have jumped the gun but I put a bid in on a Compaq Deskpro XE 560 motherboard but it did not have the riser card. Where would I find which type of riser card I should be looking for at this point?

If you find some pictures of the internals of the XE you may be able to find the part number on the riser. I have an XE 486 somewhere so i can try find it.
A complete 486 XE may be more common and i think the motherboard will fit in that. Heres how the XE looks.
Edit: I think the riser partnumber is 194374-001 and Solent Spares on eBay have them aswell as the motherboard. The downside is you only get ISA.