I was shopping around on Ebay for cheap crappy Pentium 4s to test out a bunch of old mobos (guinea pig job... risky)
The seller with the right stuff for me also had a socket 775 mobo bundled with a socket 771 Xeon, guaranteed to be working and with their usual money-back guarantees. That's a reputable seller I know already, not a random idiot trying to sell crap, so I got hyped up a bit and started investigating.
What I find is LGA 771 to 775 Adapter - Run Cheap Xeon CPUs in an LGA 775 Motherboard That is a tutorial to mod old socket 771 xeons to work in normal socket 775 mobos that support only the commercial version (non-xeon) of that processor AND have the right chipset. He sells a small strip to remap a couple pins easily http://www.ebay.it/usr/speedss5
The logic behind this is that Xeons for socket 771 are rather cheap nowadays, while the socket 775 processors beyond the midrange are horribly overpriced.
Case in point: Xeon E5450 is basically the same as Intel Core 2 quad Q9650. I can find the former for 60 euros, while the latter sells for a whopping 150+ euros or even more if new.
Also xeons overclock more easily (with a board that can do it).
High end socket 775 processors are pretty beefy in benchmarks, around 2/3rds of what a modern i5 scores, so it's a great way to keep alive older rigs in an affordable way.
There is also a thread in Overclock.net [MOD] LGA775 Support For LGA771 Xeon CPUs
and in xtremesystems.org Overclocking Thread about LGA 771 CPU on LGA 775 Mobo
Spreading the info to all cheapo guys and modding enthusiasts. :geek:
I'm probably going to try out myself as some of the boards I need to test should be theoretically capable of this, if they aren't dead anyway.