HI, sounds like you're about to try using the Xeon CPU in a 1366 board. I did the same thing - in fact, I've done two now, with another CPU being shipped...FWIW, a few comments:
The prior generation boards (socket 775 boards) have a similar 'mod', that is, using a socket 771 Xeon CPU (X5460) though in that case it requires a small 'band-aid' kind of patch to swap two pins around, and you have to either notch the chip or remove the keys in the socket, because - for whatever reason - the 771 Xeons are 90 degrees rotated and those two pins inverted, but otherwise the same as the 775s It's actually quite clever, and you just have to wonder not only who thought the original layout up, but also who realized the mod was that simple (especially since they turned around on the 1366 boards and made it so none of that was needed...)
Anyway, I did one of those 775-771 mods, and it actually helped me squeak out a little bit extra from that aging 775 board (an Asus P5N-E SLI), beyond what I could get with a QX6850. So I've got another one coming to use on a second 775 board, in the hopes it will allow the same result. It varies though, because as I'm sure you know, each CPU is different, and those older boards can sometimes be very fussy about overclocking, which limits the gain you actually get. I'm actually hoping the second board will allow better overclocking, since I can't get even an inch outta that 650i chipset Asus board (and they are known for this, apparently).
Now, of course, the 775 mod has nothing to do with what you asked about, I know - just a preface to illustrate that I've done more than one of these. As you're aware, the 1366 boards can take the X56xx Xeons, only with the 1366 boards, none of the physical mods are needed. I decided to chime in here because, basically, if you were to ask me, I'd say the 1366 mod using an X5650 just failed to impress me whatsoever. It made almost no difference in the measurable performance far as I can see, and perhaps even less in the perceived performance.
Now, granted, you're talking about using either of two faster Xeons - and maybe you have a board that you don't have a CPU for already, so it's not an "upgrade" so much as an 'initial outfitting', maybe. Taking these two things into account, maybe you're better off using the Xeon as you've inquired about.
But for me, the X5650 didn't work out well, compared to the i7-930 I had started with, the difference was pretty much non existent.
To be accurate, though, I haven't tried any overclocking yet - and maybe that's where the Xeon will shine. But, I can say this - I was far more impressed when I decided to try a 980x than with the Xeon. Of course, there's a fairly big price gap, too - but by that time, I was honestly just trying to see what I could get out of the board, price of the CPU aside within reason, and the 980x didn't disappoint. The 980x by itself wound up costing almost 3/4s of what I got the X5650 and the motherboard for...so the Xeon is definitely a more economical choice. And you do just have to love the way those old 1366 setups run; even the Xeon holds its own against some 2nd-gen i5's (and even a few 3rd-gen's, too). Alas, with X58 chipset boards, you're not getting SATA III, PCIe 3.0, nor USB 3.0, I think...so then it's off to the Z68s, Z77s, Z87s...
I look forward to hearing about your project and your results. Maybe I can help with some of the parts, too. Did you consider eBay? I've had very good luck there, trolling around looking for older stuff like this.
edit: I realized while writing about the X58 chipset features that my first 1366 board was, in fact, a Gigabyte GA-X58-USB3...so I was wrong about USB 3.0, though I still think SATA III and PCIe 3.0 are out.
Last edited by kksnowbear; 09/13/17 03:59 AM.