Oliver Costich said:
Why not the S478 3.0E or 3.2E with i1MB cache?
I'm trying to give you the best thermal performance I
know of. Page 23 lists the current drawn by the processor:
The LGA775 5xx family datasheet is here:
http://www.intel.com/design/pentium4/datashts/302351.htm
On page 23, the enhanced_auto_halt current is 31 amps for
the 3.2GHz processor, and 40 amps for the 3.0GHz processor.
That current, times whatever is the Vcore voltage, gives the
idle power for your system. The system spends more time at
idle than computing, and P4 systems tend to be space
heaters (even my 2.8GHz Northwood is annoying that way,
partially because of the ATI 9800Pro video card).
The Prescott 3.0E on socket 478 datasheet is here:
http://www.intel.com/design/pentium4/datashts/300561.htm
On page 22, the operating current of a PRB=0 processor, is
the same as the 5XX series above. Except that, the enhanced
auto halt feature is missing. The Prescott S478 will be
drawing 40 amps at idle.
You also have to watch the PRB bit, when buying processors.
On the S478, PRB=1 means the processor is in a different
"class" than a PRB=0 processor. The PRB=1 draws more
electrical power, and the PRB bit in the CPU, is an indicator
to the BIOS that more power will be drawn by the processor.
The BIOS can then decide whether it is safe to run the
processor or not, based on that flag bit. You can see in the
table, that the PRB=1 processors can draw up to 91 amps, while
the PRB=0 processors can draw 78 amps. The current is obviously
proportional to core frequency, so as you would expect, the
fastest processors are PRB=1 models. But there are a couple
of cases, where two processors run at the same speed,
yet one product is PRB=0 and the other is PRB=1.
So, if you were buying a S478 Prescott, these would be the
ones to find. (The 3.0E and slower, should all be PRB=0,
so no special searching is required for them.)
3.2E GHz (PRB=0)
3.4E GHz (PRB=0)
From processorfinder.intel.com, if you bring up the Pentium 4
processor list:
http://processorfinder.intel.com/scripts/default.asp?CHRID=483
and click Go, there are various steppings of 3.2 and 3.4GHz
processors. Now, the bad part, is there appears to be errors
in the individual entries, that is making it impossible for
me to verify which of the 3.2/3.4 ones are the good ones.
At the bottom of an individual entry, like this one:
http://processorfinder.intel.com/scripts/details.asp?sSpec=SL7KD
it says "support loadline A". I think that is supposed to be
the lower power processor, and yet the thermal rating is
listed as 103W, and not 89W.
I guess if I was buying a S478 Prescott, I would be doing it at
my local computer store, and finding a processor box with
"89 watts" written on it.
If you are shopping by price, and are not worried about heat
output, then by all means just find the cheapest one and
use it. If your room is air conditioned, it won't matter in
summertime.
One thermal limit with Prescotts, is they reduce their computing
rate automatically, when the CPU core reaches 70C. When you
install your new processor, run a copy of Asus Probe or maybe
Speedfan, and monitor the core temperature. Run a heavy computing
load, such as a burn-in application, or a copy of Prime95
(mersenne.org). With a 100% computing load running in Windows,
check the temps and see if they are getting to 70C. Sometimes
a third party heatsink/fan is required to get the temps
comfortably below 70C.
HTH,
Paul