Pentium-3 vs Pentium-4

I recently was giving away some old P3 and P4 machines and was surprised by the level of interest in P4 machines. As you can see from my page on computer power use [1] the power use from a P4 system is significantly greater than that of a P3. The conventional wisdom is that the P4 takes 1.5 times as many clock cycles to perform an instruction as a P3, the old SPEC CPU2000 results [2] seem to indicate that a 1.5GHz P4 will be about 20% faster than a 1GHz P3, but as the P4 has significantly higher memory bandwidth the benefit may be significantly greater for memory intensive applications.

But generally as a rule of thumb I would not expect a low-end P4 desktop system (EG 1.5GHz) to give much benefit over a high-end P3 desktop system (1GHz for a desktop), and a 2GHz P4 server system probably won’t give any real benefit over a 1.4GHz P3 server system. So in terms of CPU use a P4 doesn’t really offer much.

One significant limitation of many P3 systems (and most name-brand P3 desktop systems) is the fact that the Intel chipsets limited the system to 512M of RAM. This really causes problems when you want to run Xen or similar technologies. I have a few P4 1.5GHz systems that have three PC-133 DIMM sockets allowing up to 768M of RAM (it seems that PC-133 DIMMs only go up to 256M in size – at least the ones that cost less than the value of the machine). Another issue is USB 2.0 which seems to be supported on most of the early P4 systems but none of the P3 systems.

512M of RAM is plenty for light desktop use and small servers, my Thinkpad (my main machine) had only 768M of RAM until very recently and it was only Xen that compelled me to upgrade. The extra power use of a P4 is significant, my 1.5GHz P4 desktop systems use significantly more power than a Celeron 2.4GHz (which is a much faster machine and supports more RAM etc). Low-end P4 systems have little going for them except for 50% more RAM (maybe – depends on how many sockets are on the motherboard) and USB 2.0.

So it seems strange that people want to upgrade from a P3 system to a P4.

8 comments to Pentium-3 vs Pentium-4

  • Hi,

    Well people might not know that P4’s pipelining was poorly designed leading to a crappy instruction prediction (which gave birth to the P4 HT) (I’m no CPU scientist and can be wrong)

    Where the P3’s microarchitecture is still pretty awesome and is reused in today’s systems (centrino and so on)…

    This is where people who know shall tell people who don’t that’s it’s not because “4” > “3” that it’s better :-)


    (Remembers his dual 366@450MHz celeron on an Abit BP6… beated everyone at the time !)

  • Hrw

    Any P3 system with free PCI slot can get USB 2.0 support for less then 10 EUR so it is not a problem. Limit of memory size is more important.

  • Anonymous

    In general, I would agree. In certain specific cases, however, a P4 processor will indeed work significantly better than a P3 processor, even ignoring the rest of the system. For instance, video encoding fits the P4 architecture well; it keeps the pipelines full, keeps the caches full, and thus benefits from the fast clock speed and deep pipeline.

  • etbe

    Hrw: Good point. However I can buy Celeron 2.4GHz systems with 512M of RAM for $AU190 (including shipping) and a year ago I could buy P3 systems with 256M of RAM for $AU120 (now I can’t find anyone selling them) so a E10 ($AU17) upgrade for a P3 system makes a significant impact on the value for money equation. If I could still purchase P3 systems from a reliable source (not ebay) then after upgrading one to 512M of RAM and USB 2.0 the price would be approaching that of a Celeron 2.4GHz system (which incidentally supports SATA and sometimes includes a DVD drive as part of the package).

    For a machine of P3 vintage it seems that upgrading a deployed system can make economic sense (if only because of reliability issues when replacing a machine) but for a new machine it doesn’t.

    Anon: Good point about video encoding. Last time I tried such things I found the quality of live encoded video on a P3 class machine was reduced due to lack of CPU power. Of course what you REALLY want is a 64bit CPU for that sort of thing (more registers and some 64bit math really helps).

  • thanks….but how can i upgrade my pentium 3 to pentium 4…?

  • etbe

    carlo: If it’s a white-box machine you buy a new CPU and motherboard. If it’s name-brand then you buy a new machine.

  • TropiKo

    For this:
    Pentium 4 1.5 ghz gives its least on memory, and has an overall clock advantage of 10% (NOT 20% thats too much).
    Also if you overclock a pentium 3, like i do from 1ghz to 1.1 or 1.2 , the performance boost is 15 to 20%, and if you have sufficient SD-RAM, not ddr, cause ddr slows it more than improoving games and apps, you can get like 40% in games, and just a little in office applications, from what i tested, mpowerpoint.
    Also, 2 pentium 3s can easily take 2004 games and up :D , with just a small oc, 2 comermines can get over 30 or even 40 fps in games with my current Inno3D Ti4200. I’m going to upgrade to Ati radeon 9800 pro 256 mb 256-bit, its twice better as speed, memory , cycle rate, and driver support, so now nVidia is a shame for its old cards up to geforce 8000 series, even so thoose 200 gt series are expensive and not efficient.
    So my recomandation, if you still have p3s, get a dual mb like abit vp6( other amd or pentium 4 cards ARE WORTHLESS, they are old, BAD gfx card support, BAD cpus, BAD memory) and just wait for something better then the p4 and athlon 64 era( i shouldn’t include clone cpus) .
    Pentium 4 i think is the worst in intel history, not as performance, but as its existence.

    Pentium 3 lives

  • david

    Up until the start of 2009, I had a tualatin celeron 1300 running at 1.5GHz, I later pumped up the Vcore, and got 1.82GHz out of it, while changing the Vcore back down, I shorted the wrong pin (VCC–>VSS) and fried the CPU and the motherboard. The point is, before this while running at 1.5GHz my friend had a P4 1.7 and overclocked it to 1.8-1.9 GHz, my computer had a GeForce FX 5200 and he had a GeForce 7300GT, my computer still showed up that crappy P4 and when we swapped the graphics card, my computer kicked it, although he wouldn’t admit it!