What temp do skt 478 Prescotts start to clock throttle?

[Stumps]

I recently got a P4 3E (3.0ghz SL7E4) Prescott skt 478 cpu to replace an older Northwood 2.66ghz CPU that I had in a rig of mine.

I used to run the 2.66ghz at a reasonable 3.06ghz (20x153) no worries on my GA-8S648FX-L (SIS648FX) but I figured that the board supported Prescott CPU's so I went and purchased a brand new unit of Ebay for a good price.

I have recently started to give it a work out and see what it can do, I gave it a pretty nice overclock to 3.4ghz (15x227) on stock vcore and all seems well. it can run prime95 for more than 10hrs straight with out any real hassles and it rarely gets above 55c, so I'm not complaining about it.

Now I've heard a lot of stories about Prescotts being Heat monsters and clock throttling at certain temps, now what I want to know is what temps and clock speeds should the SKT 478 Prescotts start to throttle back?

 

[Duvie]

It depends on the vcore....you raise the vcore and it appears to throttle sooner. I think at stock vcore it is like 70-75c...You will need to play around with this as there are a few things...

1) inaccuracy of motherboard temperature reporting
2) when I was trying this I didn't have some of these new temp monitor programs. see if TAT or Coretemp will give more accurate temps.
3) some bios options will let you turn some of the features off causing it to happen unpredictably if at all...

 

[Stumps]

Jeez 70+c damn I not even getting close to that....

how much slower should that CPU be compared to a Northwood based P4 running at the same speed...I've noticed that my 3.06ghz Northwood is considerably faster in benchmarks like PCMark and Sisoft Sandra...both P4's are running at 3.4+ghz

 

[Duvie]

I heard once you get above 3.6ghz the prescott and northwood would start performing similarly. the longer pipeline was built for speed so once you get the speed up it will start going...I dont think there are too many apps to this day that even take advanatge of SSE3 so for the prescott it is basically trying to overcome the penalty of the longer stage pipeline versus the northwood.

 

[Stumps]

what are the limits for an aircooled(stock HSF) Prescott as far as overclocking goes....3.4ghz was easy as pie to reach and it was the first speed I tried.

 

[Duvie]

Stock HSF maybe 3.6ghz...aftermarket air maybe 3.8ghz....

As far as I can remember. Its been awhile....LOL

 

[Stumps]

yeah, I haven't mucked around with overclocking P4's in awhile and most of my knowledge on them is based on the the Northwood P4's not the Prescotts.

 

[Duvie]

Originally posted by: Stumps
yeah, I haven't mucked around with overclocking P4's in awhile and most of my knowledge on them is based on the the Northwood P4's not the Prescotts.

same with me......

 

[AstroGuardian]

Northwoods OC better since they have FSB533. I also had better OC experience with northwood. OC'ing Prescott requires far better mobo.

 

[stevty2889]

Originally posted by: AstroGuardian
Northwoods OC better since they have FSB533. I also had better OC experience with northwood. OC'ing Prescott requires far better mobo.

There are 800mhz FSB Northwoods as well..

When I had my 3.06ghz northwood overclocked to 3.43ghz, it was able to keep up with, and sometimes beat my Prescott at 3.8ghz in several applications. The Northwood was still faster when it came to gaming, MP3 encoding, while the prescott was faster at video encoding. I couldn't get my 3.4ghz 5xx series prescott to stop throttling at stock speeds let alone overclocked on aircooling, but it's typicaly around 75c with no vcore increase. My first prescott was a 2.8ghz socket 478 that was overclocked to 3.5ghz, and it ran at similar temps to yours, but my LGA775 5xx series ran way hotter.

 

[Stumps]

Originally posted by: stevty2889

Originally posted by: AstroGuardian
Northwoods OC better since they have FSB533. I also had better OC experience with northwood. OC'ing Prescott requires far better mobo.

There are 800mhz FSB Northwoods as well..

When I had my 3.06ghz northwood overclocked to 3.43ghz, it was able to keep up with, and sometimes beat my Prescott at 3.8ghz in several applications. The Northwood was still faster when it came to gaming, MP3 encoding, while the prescott was faster at video encoding. I couldn't get my 3.4ghz 5xx series prescott to stop throttling at stock speeds let alone overclocked on aircooling, but it's typicaly around 75c with no vcore increase. My first prescott was a 2.8ghz socket 478 that was overclocked to 3.5ghz, and it ran at similar temps to yours, but my LGA775 5xx series ran way hotter.

thats pretty much how the benchmarks of my 3.06@3.45ghz look, it generally performs around 3.6/3.8ghz Prescott level...very impressive for an older P4.

I did manage to get my "new" Prescott upto 3.6ghz (240x15 1.47v) without any problems, it does run pretty hot generally around 62-65C at full load.

I'm just suprised at the big difference in the performance of both P4's, i would have figured that a prescott would be closer to Northwood performance than it really is.

 

[SuperNaruto]

Found this on a website.. basically I sold the prescott processor and bought northwood

--
Why doesn't the Prescott with its twice larger L1 and L2 caches and architectural enhancements outperform the Northwood with ease? (refer to table above for numbers)

Prescott Advantages over the Northwood:
1. Twice larger L1 cache.
2. Twice larger L2 cache.
3. Integer Shift/rotate functions can run much faster due to improved ALU
4. Integer Multiply functions are much faster due to new dedicated integer multiplier (Northwood integer multiplies are done by the FPU unit)
5. New improved branch predictor to reduce pipeline stalls

Prescott Cache Disadvantages compared to Northwood:
1. Double the L1 cache latency
2. ~50% higher L2 cache latency
3. Half the L2 cache bandwith
4. 50% longer pipeline