View Full Version : Pentium 4 CPUs

bk T
27-07-2004, 12:07 PM
1. P4 2.8E Prescott 533 1M L2 Cache
2. P4 2.8C 478 800 FSB Northwood

Which of the above is better in terms of performance and "value for money"?


27-07-2004, 12:35 PM
well that depends......if you have a 533Mhz board then the 800Mhz processor is gonna be wasted in a bottleneck .....if you have a 800Mhz board then the 533 cpu wont be taking full advantage of the rest of the system........

Pete O\'Neil
27-07-2004, 01:07 PM
Do they even make a 533MHZ FSB 2.8GHz Prescott P4? I know they made a 2.4Ghz Prescott with a 533ZMHz FSB, damm good overclocker aswell. If they do make a 2.8Ghz chip with a 533MHz FSB it too could be a good overclocker.

Assuming both those chips are socket 478 then the Northwood would easily out preform the Prescott (assuming you have a modern motherboard capable of running the FSB @ 800MHz and ram capable of 200MHz). There should be much difference in price. Although the Northwood might be a bit hard to find now.

27-07-2004, 02:03 PM
Try this link, it compares all CPUs.


27-07-2004, 02:05 PM
Correction ... If not "all" CPUs then at least most or many.

Pete O\'Neil
27-07-2004, 03:54 PM
that link is kinda irrelevant as it makes no differentiation between the different cores.

Due to the Prescotts longer pipeline its doesnt preform aswell as the Northwood at the clockspeed. (there are some exceptions to this rule e.g Skt775 and the latest ATI chipset for the P4). The aboves chips lack of FSB will also cripple it. It has been shown through benchmarking that the P4 continues to benefit from an increased FSB until around 1066MHz.

27-07-2004, 04:27 PM
>>no differentiation between the different cores.

Pete, could you explain what is meant by 'different cores'? Thanks.

27-07-2004, 04:37 PM
> Assuming both those chips are socket 478 then the
> Northwood would easily out preform the Prescott
> (assuming you have a modern motherboard capable of
> running the FSB @ 800MHz and ram capable of 200MHz).

Is the 200MHz RAM correct? I though you would maximise the potential of the PC (with the 800MHz FSB processor) by using 400MHz RAM (e.g. PC3200 DDR400). Was this a typo Pete or am I mis-interpreting your numbers?

Pete O\'Neil
27-07-2004, 06:03 PM
Over the lifetime of the Pentium 4 it has had several different cores. The first being the Willemette, followed by the Northwood, now we're seeing the Prescott, and there also the core used in the Extreme Edtions (cant remember the cores name but its just a rebadged Xeon). Each core offers differing preformance and in theory the newer cores should out preform the older cores. Now this is where things start to get tricky, as chipset and ram affect preformance.

The original Willemette core, originally used RAMBUS ram, and later SD-RAM, RAMBUS had **** loads of bandwidth and didnt bottleneck the CPU what so ever. SD-RAM was a budget solution and really held the P4 back meaning it didnt preform very well. One of the biggest problems with teh Willemette core was that at the same clock speed it was out preformed by the P3. This mean there was little insentive for P3 users to upgrade, there was little preformance gain and the cost of RAMBUS was crazy. As the P4 began to scale it evenually showed imporements over the stagnent P3.

Intel next released the the Northwood core if i remember correctly the lvl2 cache was increased to 512kb and the FSB was eventually increased to 533MHz. At this point Intel adobted DDR(pioneered by its arch nemsis AMD muhahaha), offer a cheaper alternative to RAMBUS. A northwood @ 2.8Ghz would out preform a willemette @ 2.8Ghz based on the the increased lvl2 cache and FSB(assuming they were using the same ram). The northwood also benefitted from core tweaks (note the pipeline stayed the same). It was at this stage the P4 finally started to show its hand easily scaling past the fastest Athlon. Withen the last 6months the FSB of the Northwood was scaled to 800MHz once again increasing the preformance of the P4 e.g a 2.8Ghz 533mhz FSB was slower than a 2.8Ghz 800MHz FSB.

Just recently Intel released the Prescott core, and this is where things get interesting. Intel increased the lvl2 cache and kept the FSB the same so in theory the Prescott should out preform a Northwood. But there was one funemental change that meant this wasnt the case, Intel increase teh P4's pipeline from 20 stages to 31. The shorter the pipeline the quicker the CPU is at a given Clock speed. Only problem is a shorter pipeline affects scalabilty e.g clock speed. This is the primary reason why AMD isnt able to match Intel clock for clock. (AMD choose to have a lower overall clock speed to be more effective at the given clock speed). When Intel released the prescott it was widely accepted amongest conspiracy theorists that it was released early due to the success of the AMD64. Just before this point Dual Channel DDR was introduced and Intel finally had a cost effective answer to RAMBUS that didnt lack in preformance. This meant that the chipsets on the market (865 & 875)at the time were never designed to run a Prescott. This meant that when it was released the Prescott was slower than a northwood at a given clockspeed even though on paper it looked more appealing. E.g a 2.8Ghz Northwood outpreformed a 2.8Ghz Prescott.

Once again things have now changed and with the arrival on Intels new chipsets and socket the Prescott is now faster than the Northwood, but only if your buying a Socket 775 chip, which isnt the case.

Now i seem to have gone overboard but hopefully ive shown that there are difference between the different cores. Thus the above website that doesnt differenciant between core is a waste of time as the above CPU are both of the same clock speed.

This repsonce probably has heaps of grammer errors, but since its 5pm and i want to go home it'll have to do. The likes of Whetu and Melta will probably find a few errors but on a whole it should be pretty accurate. Not bad for a AMD fanboy aye?

27-07-2004, 06:23 PM
very informative - thanks Pete

Pete O\'Neil
27-07-2004, 07:04 PM
> Is the 200MHz RAM correct? I though you would
> maximise the potential of the PC (with the 800MHz FSB
> processor) by using 400MHz RAM (e.g. PC3200 DDR400).
> Was this a typo Pete or am I mis-interpreting your
> numbers?

Ok now to answer your question, sorry i didnt answer it early but like most people i try to get out of work as early as possiable.

DDR400 (PC3200) is exactly the same ass 200MHz ram, its all to do with the way DDR handles data. Now once again can i please warn you that my terminology when it comes to RAM is flawed so dont take my reasoning as gospel. In basic english DDR is able to compute 2 peices of data in the time older SD-RAM took to do one peice of data. That is why DDR running at 200MHz is refered to as DDR400 or 400MHz. The rating of PC3200 come from the about of bandwidth DDR400 is able to provide, which just happends to be 3.2Gb/s. (8x200, the 8 is all to do with bits and byte etc).

Both the Athlon XP and Pentium 4 have a FSB of 200MHz, its just that both companies use some creative marketing. The Pentium 4 is able to quad pump the FSB, meaning it effectifly has a FSB of 800MHz. Where as the Athlon double pumps the FSB, meaning it effectifly has a FSB of 400MHz. You average n00b will imediatly jump out and say the Pentium 4 is better because it has a higher FSB, but one must remember that we are dealing with two completely differnet CPU architectures. The Athlon doesnt need a FSB anywhere near as high as the P4, when AMD increased the Athlons FSB from 333 to 400 it showed only a marginal increase in preformance. Where as the Pentium 4 has shown improved preformance each time Intel has increased the FSB. Through overclocking it has been shown that the P4 continues to gain from the increase in FSB up unitl around the 1066MHz mark. Intel is expected to release a Extreme Edtion relatively soon with a 1066MHz FSB, thus confirm what the overclocking community has know for a long time.

All this infomation is soon to become irrelevant as Intel has recently released its new chipset supporting DDR2 which works in a different way to DDR1. To make thing easy im going to ingore the existance of skt775 as it makes things to complicated. To get the best preformance from a P4 one must remember that the P4 now support Dual Channel Memory. This is where two memory controllers are used to effectivly double the avaliable memory bandwidth e.g with DDR400 from 3.2GB/s to 6.4Gb/s. These means that you need to matching sticks of RAM, you can use a single stick of ram in boards supporting dual channel with out a problem it just means dual channel wont be enabled. Currently there are only a handful of chipset on the market supporting dual channel. The intel 865 and 875 aswell as a VIA chipset the PT880 (dont quote me on that). Dual channel memory can offer up to a %20 increase in preformance for the P4(the Athlon doesnt really benefit from dual channel). There are motherboards floating around using the Intel 848P chipset that support 800MHz FSB chip but only use single channel ram, these really should be avoided if at all possiable. There fine for your average home computer but when it only cost a few dollars more a board based on the 865 is a superior choice.

You might see when shopping at computer store Dual Channel RAM kits, these are nothing special they are mearly two sticks of ram guaranteed to run in dual channel mode, they have been tested by the manufactuer. It is possiable to buy two different sticks of RAM and make them run it dual channel but its best to buy a dual channel kit or two identical sticks.

bk T
27-07-2004, 07:23 PM
Thanks, Pete. Excellent input and information.

27-07-2004, 09:09 PM
thanks again Pete - it is all crystal clear (and so obvious now, DDR = double data rate and I was wondering why the big jump from 133Mhz to 400) so please accept my apologies for questioning your numbers - one thing I do know is that the more I know the more I realise I don't know

regarding fsb ratings (and the marketing hype), this (http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?query=fsb) site helps explain it too

28-07-2004, 10:30 AM
Pete, thanks very much for an informative explanation of 'cores'. Now I have completed yet another chapter of my geek-tech training. :)

The cpuscorecard web site does list the cores, or at least for the couple of CPUs that I clicked on. Although the specs of each core are listed, a comparison is not given. Also, the information is somewhat dated in that the latest data is missing. For $9.95 a year extra info is given.

A few weeks ago I read a couple of articles on Prescott's longer pipeline. I seem to recall that other features of Prescott made up for the increase in stages. Thought I saved the articles to the HD but cannot find them now.

One basic point - perhaps you or others could clarify: Marketing hype can feature a fast new CPU, AMD or P4, but usually will not mention the motherboard. Putting a fast expensive CPU on a cheap MB with an inferiour chipset will cause the CPU to underperform - is this correct?

Pete O\'Neil
28-07-2004, 11:55 AM
Yes chipset do make a big difference when it come to the preformance of a CPU. Quite often a chipset will be designed to work with a particular core, this doesnt mean it wont work with others cores it just wont offer the best preformance possiable. This is the main reason why in Bk T other post i reckonmended changing the motherboard.

For example to get the best preformance from a Northwood based Pentium 4 processor its best to use a motherboard that uses Intel's 865 or 875 chipsets. The main benefit these chipsets have over the 848 is that the both support Dual Channel RAM. At 800MHz the P4 requires 6.4Gb/s exactly the same amount of bandwidth dual channel DDR provides, using single channel only 3.2GB/s is avaliable causing a bottleneck and limiting the CPU's preformance. With the Pentium 4 the use of Dual channel can offer around a 10-20% preformance increase depending on application.

As i said in an earlier post it is rumored that Intel brought foward the release date of Prescott due to the success of AMD64. Intel initially planned to only release prescott on socket 775 with its new 9XX chipsets and DDR2. It has been shown that the socket 775 variant of Prescott preforms aswell if not better than socket 478 varient of Northwood.

But as well all know Prescott was originally released in a socket 478 format, this meant that Prescott was forced used with 8XX chipset that were originally designed for use with Northwood. So when comparing a Prescott and Northwood both using the socket 478 format at the same clock speed the Northwood is the winner purely because of its shorter pipeline. Intel did make enhancements in other areas of Prescotts design to compensate for the longer pipeline but these were unable to make up for the fact that prescott was forced to run on a platform it wasnt designed for. Intel increased the Lvl2 cache and improved hyperthreading preformance but neither of these were able to compensate for a longer pipeline and a chipset designed for an older core. If your a regular reading of news on the internet you may remember there was a lot of problems with motherboards not being Prescott compatiable, this just further reinforces the case for Prescott being released early.

Now there is actually one way to get a prescott to run faster than a Northwood with socket 478. ATi recently got into the motherboard chipset market, offering chipset for Intel very similar to the way nvidia offers chipsets for AMD. Now ATi's first chipset was utter cr@p lacking features and preformance, much like the original nForce :). But about 1 month ago they released RS350 which is tweaked to offer best preformance with a Prescott based P4. Using this chipset a socket 478 Prescott outpreforms a Northwood socket 478(using the 875 chipset) at the same speed.

At the end of the day if your building a system based on socket 478 then use a Northwood P4 with a 865/875 chipset. This is one of the reasons alot of PC enthusiast reckonmend choosing your motherboard and ram before you choose your CPU. That doesnt mean you dont choose P4 it just means you choose your clockspeed and core after youve found you motherboard and ram.