Intel's Pentium 4 E: Prescott Arrives with Luggage
by Anand Lal Shimpi & Derek Wilson on February 1, 2004 3:06 PM EST- Posted in
- CPUs
Execution Core Improvements
Intel lengthened the pipeline on Prescott but they did not give the CPU any new execution units; so basically the chip can run faster to crunch more data, but at the same speeds there are no enhancements to work any faster.
Despite the lack of any new execution units (this is nothing to complain about, remember the Athlon 64 has the same number of execution units as the Athlon XP), Intel did make two very important changes to the Prescott core that were made possible because of the move to 90nm.
Both of these changes can positively impact integer multiply operations; with one being a bit more positive than the other. Let us explain:
The Pentium 4 has three Arithmetic and Logic Units (ALUs) that handle integer code (code that operates on integer values - the vast majority of code you run on your PC). Two of these ALUs can crank out operations twice every clock cycle, and thus Intel marketing calls them "double pumped" and says that they operate at twice the CPU's clock speed. These ALUs are used for simple instructions that are easily executed within 1/2 of a clock cycle, this helps the Pentium 4 reach very high clock speeds (the doing less work per cycle principle).
More complicated instructions are sent to a separate ALU that runs at the core frequency, so that instead of complex instructions slowing down the entire CPU, the Pentium 4 can run at its high clock speeds without being bogged down by these complex instructions.
Before Prescott, one type of operation that would run on the slow ALU was a shift/rotate. One place where shifts are used is when multiplying by 2; if you want to multiply a number in binary by 2 you can simply shift the bits of the number to the left by 1 bit - the resulting value is the original number multiplied by 2.
In Prescott, a shift/rotate block has been added to one of the fast ALUs so that simple shifts/rotates may execute quickly.
The next improvement comes with actual integer multiplies; before Prescott, all integer multiplies were actually done on the floating point multiply unit and then sent back to the ALUs. Intel finally included a dedicated integer multiplier in Prescott, thanks to the ability to cram more 90nm transistors into a die size smaller than before. The inclusion of a dedicated integer multiplier is the cause of Prescott's "reduced integer multiply" claim.
Integer multiplies are quite common in all types of code, especially where array traversal is involved.
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mattsaccount - Sunday, February 1, 2004 - link
From the HardOCP review: "Certainly moving to watercooling helped us out a great deal. In fact it is hard for us to recommend buying a Prescott and cooling it any other way."eBauer - Sunday, February 1, 2004 - link
I am curious as to why the UT2k3 botmatch scores dropped on all CPU's... Different map?Pumpkinierre - Sunday, February 1, 2004 - link
Sorry errata on #20 that was 3.0 Northood result is out of kilter with other cpus in dtata analysis sysmark 2004.Pumpkinierre - Sunday, February 1, 2004 - link
JFK,Vietnam,Nixon,Monica,Bush/Gore,Iraq and now this! - what is going on with the leader of the free world.I hope it overclocks well- that's all that's going for it. Maybe Intel should rethink their multiplier locked policy. AMD must get in there and profit. I still dont understand why the caches are running at half the latency as Northood if they are the same speed and structure? Is it as a result of a doubling in size for the same associativity?Good article- needs re-rereading after digestion. Last chart in Sysmark2004 (data analysis) has 3.0 Prescott totally outperformed by 2.8 Prescott and all other cpus. Look like a benchmark/typing glitch.
yak8998 - Sunday, February 1, 2004 - link
first the error:pg 9 -
The LDDQU instruction is one Intel is particularly proud of as it helps accelerate video encoding and it is implemented in the DivX 5.1.1 codec. More information on how it is used can be found in Intel’s developer documentation here.
No link?
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"What's the power consumption like on these new bad boys?
Is anything less than a quality 450watt PSU gonna be generally *NOT* recommended?? "
I'm going to guess a clean running ~350W or so should suffice for a regular system, but I'm not positive with these monster gfx cards out rite now...
"Any of you know what the cache size on the EE's will be?"
If your talking about the Northwood (the p4c's are still considered northwoods, no?), its 1mb I believe.
(still finishing the article. man i love these in-depth technical articles)
Tiorapatea - Sunday, February 1, 2004 - link
I agree, some info on power consumption please.Thanks for the article, by the way.
I guess we'll have to wait and see how Prescott ramps in speed versus 90nm A64.
AgaBooga - Sunday, February 1, 2004 - link
Much better than the P4's origional launch...All I want to know now is what AMD is going to do soon... They'll probably counteract Prescott with high clock speeds but when and by how much is what matters.
Any of you know what the cache size on the EE's will be?
Also, the final CPU's based on Northwood are kind of like a car with the ratio curves or whatever they're called, but basically after a point of revving, going any higher doesn't give you as much of an increase in speed as it would at a lower rpm increasing the same amount.
Cygni - Sunday, February 1, 2004 - link
AMD's roadmap shows a 4000+ Athlon64 by the end of the year... which is the same as Intel's. They are aware, im sure.Stlr22 - Sunday, February 1, 2004 - link
What's the power consumption like on these new bad boys?Is anything less than a quality 450watt PSU gonna be generally *NOT* recommended??
HammerFan - Sunday, February 1, 2004 - link
Things are gonna get hairy in '04 and '05!!! My take is that AMD nees to get their marketing up-to-spec or the high-clocked prescotts are gonna run the show.I have a question for Derek and Anand: What kind of temps does the prescott run at? what type of cooler does it have? (there's nothing there to support or refute claims that the prescott is one hot potato)