Many people seem to have no idea about the differences between the Northwood and the Prescott. This guide will hopefully give a rough idea about the performance difference (or lack thereof) between the Northwood and the Prescott P4.

Info from this thread is a result of compiling and analyzing data from various webpages and some intel tech documents.
Some of the references:
http://www.aceshardware.com/
http://www.digit-life.com/articles2/rmma/rmma-p4.html
http://www.anandtech.com/cpu/showdoc.html?i=1956

Below is a list of basic differences between the Northwood and Prescott. More details to come soon.

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The big question:
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


ANALYSIS:
1) Although the cache sizes of the Prescott are twice higher, the cache latencies are also greatly increased, which somewhat offsets the increase in cache size. Caches generally work best when they are small and fast, not big and slow.
Also, according to the testing done by the guys at Digit-Life, the Prescott's L2 bandwith is only half of the Northwood. Perhaps intel reduced the Prescott's L2 bus width to 128bit (Northwood is 256bit).

2) The larger cache can barely offset the performance of the 50% longer pipeline (31 vs 21 stages). Longer pipelines means that a pipeline stall (due to branch misprediction) will be much more detrimental to the performance.

CONCLUSIONS:
Due to 1) and 2) above, the Prescott's performance is slightly lower than the Northwood in most situations, but they are roughly on par with each other.

An interesting observation made by the guys at Aceshardware is the power consumed per transistor of the Prescott. It is actually ~46% lower than the Northwood! But the immense number of transistors (more than double the Northwood) add up to make the total heat output higher.


So if you are looking for a P4 at the moment is get a Nortwood and stay away from the Prescott until Intel fixes the heat issue with the Prescotts, because the Prescotts feature a much higher heat output and lower performance than the Northwood.

This high power usage and heat output is due to the transistors leaking a lot of current ( 40% even in the OFF state!) with the new 90nm manufacturing process. The problem is happening with everyone's 90nm process (yes, AMD and IBM included) at speeds roughly above 2.5GHz.

oops sorry, i'll fix it

Guys, hope you don't mind me deleting your posts, nothing wrong with them, i just want to make my follow up post right below my main post ok? Easier for ppl to read that way

You can repost if you want

And of course if you guys notice some errors in my posts or have new info to add, please do so.

Why not just go for AMD. Single channel Athlon64 can easily match Northwood performance in 32-bit. Plus the potential performance gain when you switch to 64-bit.

maybe because of price factor and overclockability

also, may be bcoz this thread is

Northwood vs Prescott GUIDE

not amd vs intel

read the title "dude"

Well i was just making a technical comparison between the two different P4 architectures. I was not comparing against AMD at all here. Rephrased the final sentence.

OK, I'm sorry for mentioning AMD here. It's not my intention to create another "Intel vs AMD" debate here.

Don't you think that Intel's designing strategy has gone wrong ? A newer chips run even slower than the older one. And they have problem to increase the core frequency due to the excessive heat.

HAhahah....
suddenly change to AMD pulak..

I think P4E will sure catch up and perform faster than P4C. Later, will there be presscott with 1000mhz/1200mhz FSB ? I think this will really boost presscott's performance...

haha, yeah... i agree that technically, there might be sum problem.
when they 1st introduce P4, willimate / 1st version of northwood, it's performance was really a crap. But now it has caught up AMD XP and surpass XP range (not AMD64) at high-end range.

Anyway.... it's good to stay away from P4E .... Getting P4C or AMD64 is another discussion.. haha, though I would definitely go for ..64.

is pentium4 2.4A a prescott???

yes..533fsb w/o HT.

oh?
betul ke?
Presscott has got 533FSB?

I thought it's a Northwood?

Nice 1 there ikanayam . So we hope there's no more stupid thread again , and shouldn't u pin it up ?

2.4A is Northwood. Prescott has an 'E' notation.

2.4A IS a PRESCOTT dude

It comes with 1mb of L2 cache and SSE3 instructions. The only thing is without HT and its 533 Mhz FSB

Did a quick search and found out that there is 2.4A Prescott. That's indeed confusing because there is a 2.4A Northwood as well.

i know it have 2.80A
now have 2.4A already ???

This post has been edited by |tanium2: Apr 1 2004, 04:12 PM

Actually there's two version of 2.4A, northwood and prescott. The difference can be notice by looking at the S-code at the side of the box.

Btw, here's a article on 2.4A prescott overclocking.

http://www.hardocp.com/article.html?art=NjAz

This post has been edited by shady86: Apr 1 2004, 05:23 PM

Speaking of this new Precott, I see that it supports SSE3.

What extra does this SSE3 has to offer ? And what kind of application will take more advantage of it ?

Thanks for all the info.