I've been following this thread for two months or so-- incredible resource.
Now that I swapped in an L5639 for my i7-950, I might as well add a datapoint-- particularly because I'm using this in a dual-boot Mavericks Hackintosh/Win7 system.
This is on a Gigabyte X58A-UD3R v. 2 with FH BIOS, 12GB (6 x 2GB XMS3 Corsair RAM), and an old XFX 5770 single-slot GPU (driving an Apple Cinema Display 27 LED), 1x SSD, 3X HDD, DVD-RW.
Previous system was a 3.93ghz i7-950 (171 x 23), same components, higher voltages, much higher temps. In Mavericks: Cinebench 11.5 multi CPU of 6.90, Geekbench2 64 bit ~12,500.
Current is 3.60ghz l5639 (200 x 18),
VCore ~1.110 w/ dynamic vcore +.123,
QPI/VTT 1.3.
Top temp I've ever seen in IBT is 59C, top I've ever seen in actual use (multithreaded video work, Mavericks) is 55C, usually <50C in hard tasks and <40 for normal stuff, and right around 30 at idle. This is on my hottest core, the rest of the cores are about 5-8c cooler... bad thermal paste job?)-- so it's common to have a few cores <30c.
In Mavericks: Cinebench 11.5 multi cpu of 9.30, Geekbench2 64 bit of 16,500.
I haven't tried to either optimize voltages or go for a max overclock. I'd expect to get to BCLK of 210 without much work, or be able to lower my voltages, particularly QPI/VTT (though I am running w/ all DIMM slots populated).
I also have my RAM running very slow. It's rated for 1.65 volts and 1600mhz, but I've got it at 1.66 volts (board's first stop over 1.65, though it shows as 1.63 in Mavericks) and 1200mhz (6x multi). QPI is 36X (7.2Ghz) and Uncore is 13x (2.6ghz). There's obviously room for me to move on RAM/Uncore, BCLK, and/or voltages. I think the low DIMM/UNCORE multis are the reason for my relatively low (9.30) Cinebench score given the current overclock on CPU.
All C-States, EIST, Level 1 LLC, HT, Turbo and all advanced CPU features turned on.
One peculiar thing is that in Windows I see the 20X multi getting hit on 1-2 cores at a time for 4.0 Ghz, and my single-core Cinebench score in Windows demonstrates this.
In Mavericks I only see all 6 cores move together, from 12x (2.40ghz) to 18x (3.60ghz)-- and never get any multis higher even on one core at a time--and in Cinebench single-core my score is lower than in Windows (though the multi cpu scores are identical). Mavericks is also reporting itself as "3.4 Ghz 6-Core Intel Xeon" though it's clearly hitting 3.6 across all cores under load. Idle voltages in Mavericks showing 1.008 volts.
Anyway, that might not be very helpful to you folks. But maybe someone can glean some information from this. Particularly that it works in Mavericks in a Hackintosh system almost perfectly (minus the 20x Turbo on one or two cores that I haven't figured out yet; I had turbo turned off on my 950, and I mostly do heavily multithreaded stuff on Mavericks so I don't care about 1-2 core scores).
Oh, and this is my first post here. Cheers.