I have been playing with a 955XE for the last couple of weeks and I think there are too many quick conclusions made here.
1. It's perfectly normal for Intel to stock up chips to a launch. I remembered buying a 630 as soon as they were available here (around feb 2005) and it was made 0438 which is quite early for the 2MB version.
What am I saying with this? I believe that Intel have been producing these chips for the last 5-6 month or so and in the beginning of a new series like this, the performance varies a lot, therefor a big difference in how the lowest and the highest CPUs overclock. (because of heavy binning in the beginning)
To be safe to get a good overclocking chip, go for a 955 or a 950 at least, or wait until the big retailers have run out of stock ones or twice so they might have newer chips/later production date.
(To return to my example: A friend of mine bought a 640 two months ago which overclocked like most 670 cpus do)
*EDIT* Sorry batboy, I missed your post, I'm writing about the exact thing that you wrote
2. We are talking about dual core CPUs, twice the things can go wrong. We also have twice the cache and ultimately: twice the heat (compared to cedarmill, not prescott)
There is a reason why these chips are released with a 3.46GHz part as the fastest one. They are really though to cool. Review sites have managed to get it to throttle at default speeds and default vcore and I have been able to do it myself too, inside a closed but ok ventilated chassi. I don't think these are intended to be able to run four instances of prime with stock cooling in a chassi, honestly.
I think it's a good thing to collect stats about how different chips overclock and I think it is a good idea to bring in the FPO/Batch codes in as well, so we might be able to see when the lower graded chips starts to overclock like the higher graded, and also which plants that produce the best chips.
Here's my contribution
955XE - L534 (Malay, week 34, 2005)
P5WD5 Premium
Stock cooler:
1.3v - 4GHz - can complete most benchmarks without trouble, will throttle with 4xPrime
1.3v - 4.32GHz - SuperPi 1M pass
Haven't played that much with the stock cooler, heat is a serious issue.
Watercooling
1.4v - 4.2GHz - 4xPrime stable for more than 1 hour
1.5v - 4.45GHz - 4xPrime stable
1.6v - 4.62GHz - 4xPrime for more than 1 hour.
as a side not here, the Watt-meter before my PSU showed 460W continuosly during this time, and over 500W when I started 3DMark05
Single stage unit (~-40C evap temp)
SuperPi 1M stable frequencies:
1.400 - 5090
1.450 - 5260
1.500 - 5344
1.525 - 5400
1.550 - 5450
1.575 - 5462
3DMark 03 stable @ 5200 with 1.550vcore
Cascade (~-100C evap temp)
SueprPi 1M stable
1.400 5360
1.450 5434
1.500 5544
1.550 5671
1.575 5733
1.600 5823
3DMark 03 stable @ 5400 with 1.500vcore (the cascade can't keep the temps long enough at 1.6v, higher speeds are definitely possible if you can keep the temps)
I don't like to speculate on how well these will overclock but they are definitely too hot for serious overclocking with air coolers if you ask me.