I followed up a lead today. I don't think this is quite a haul, I didn't really buy it, it wasn't a dumpster...
I got some 12V PSUs for free POS terminals (maybe more later, not sure if *anything* is working and they are perhaps retro-ish but not vintage - probably an Atom Celeron rather than a classic Celeron). The problem is some maroon cut off the system-end cables, out of spite or whatever.
So, that was annoying. BUT I discovered the PSU bricks were screwed together instead of glued, AND the cases are keyed so you can't assemble the wrong way, AND the 4-pin connector which is missing only has the two wires from the PSU board, so it's basically 12V and ground, which is cake. I can do wiring but I will need to buy a connector (maybe I can bodge something to test - again not sure if any of these work). Unfortunately the shielding on the PSU board is soldered on, so removing those wires will be slightly tricky (and installing new ones trickier). But basically two leads should not be that hard to do even with a 4-pin connector. The only reason I can think of to use a 4-pin connector with two ground and two 12V from one pair of wires from the PSU is to make the system non-standard to sell replacement parts.
I will have to take down the POS system (which is very compact) to see if there are even four wires out of the connector on the other side, if it's just two, then I could just replace both connectors with something I have in stock or is less than $5 for one end of the connector. But I have a few PSUs I can mod in either case. The 4-pin appears to be a keyed Kycon KPPX-4P.
Unfortunately, search engines are incapable of distinguishing between electronic parts stores, electronics stores, electrical supply stores, and electronics repairs stores, so I guess I will have to mail order if I can't find that 4-pin PSU my brain says I have somewhere.
I did get a socket 775 system but I haven't even taken it out of the car yet. HP but for some inane reason I lurv HP slimlines. Has a GT210 - so I'm thinking, that's about as fast as an X11950, right? Socket 775? 2006-2007 early Win7 build? I think like this sometimes.