P4 Underclocking?

I have a 2.53GHz P4 on a P4S5A motherboard with 256MB PC2700, running Windows XP. If I right click "My Computer" and choose properties, I can see my CPU is "Pentium(R)4 CPU 2.53GHz". On the next line, a line I have been told elsewhere is the actual processor speed, it says, without any title or caption, "1.89 GHz".

Also I have noticed that when I reboot the system, the black and white boot screen says Pentium 4 1.9 GHz or similar, (disappears quickly).

I have never overclocked it, (wouldn't know how), searching this board I found a couple of threads that dealt with older type boards where you could set the speed, but my board doesn't seem to have any of these options.

Apart from a real funny where it crashed during a Windows Update session and managed to switch the hard drive off in the BIOS, the system has been and is running fine.


Am I underclocking?

How do I fix it?

How could it have happened?

Med venlig hilsen,
16 answers Last reply
More about underclocking
  1. Yes, you´re only using a 400Mhz FSB. That amounts to 75% of your processor´s capability only. Your processor is capable of 533Mhz FSB, and uses a multiplier of 19, as in 19x133=2533Mhz, but it´s only using a 100Mhz-clocked FSB, QDR, meaning 19x100Mhz=1900Mhz only.

    OK, so usually, it´d be a simple matter of enabling something in your BIOS. Sometimes, you´ll also need a BIOS revision or something, but...

    It <i>might</i> also be possible that your motherboard <i>doesn´t</i> support a 533Mhz FSB. I´m not sure, so I won´t scare you with that... I´ll check. It´s a SiS645 (NOT SiS645E) based mobo, isn´t it? Look at the <A HREF="http://www.msi.com.tw/program/support/cpu_support/cpu/spt_cpu_detail.php?UID=404&NAME=MS-6737" target="_new">compatibility tables</A>... Maybe someone did something about it, tough... I´ll check the net if there´s something you can do... What about your manual, anything on it? Anyone here know about this?<P ID="edit"><FONT SIZE=-1><EM>Edited by Mephistopheles on 03/20/03 09:56 AM.</EM></FONT></P>
  2. The manual that came with the board says "SiS 645/SiS 645DX and SiS 961" chipsets.

    In another place, it says "Note: SiS 645DX Northbridge supports up to 533MHz Frontside bus". Presumably I have to take the thing apart to find out if I have a 645 or 645DX "Northbridge", (assuming I'll even recognise it!), or can I find out via some software route?

    Med venlig hilsen,
  3. Hm, no, I don´t think taking the whole thing apart would help you right now... Have you tried the BIOS setup? There might be something there, even about enabling 533Mhz FSB. Also, that black-and-white startup screen might contain info. Other software routes include SiSoft Sandra, a benchmarking utility that can also tell a lot about your system. Look into XP´s control panel, in Device Manager, there might be some info as well.
  4. I opened the box, but what I think are the "Northbridge" and "Southbridge" chips are covered with elaborate looking heatsinks, so I have not taken it apart any further, (I am using it again now). What I did see is a label on the board which says "P4S5A/DX+" and armed with that little nugget, when I rebooted, (several times before I saw it), there is a note to that effect on the startup screen. I am, therefore guessing it is a 645DX chip and thus should be capable of 533MHz FSB.

    There are some board specs here...


    >>> SiSoft Sandra

    I'll look for that.

    In the manual, there is a BIOS page called "CPU PnP Setup Page". On this page the options are...

    CPU Type: Intel P4 (Intel P4)
    CPU/DRAM speed: 100/100 MHz (100/100 Mhz) ***
    CPU Core voltage: 1.616V (1.504V)
    CPU Ratio: H/W Trap (LOCKED) ***
    CPU Frequency: 100MHz (100MHz)
    DRAM Frequency: 100MHz (100MHz)

    The first value after each item is the value printed in the manual, the value in brackets is what I have. The two values marked *** allow me to tab to them, the others not. I have not changed anything.

    I can't see much else in the BIOS that looks relevent, but to be really honest, I do not understand all of it.

    Med venlig hilsen,
    adrianxw<P ID="edit"><FONT SIZE=-1><EM>Edited by adrianxw on 03/20/03 05:52 PM.</EM></FONT></P>
  5. So it probably does support 533Mhz FSB.

    Check the BIOS setup - if you press delete on startup, or something, you´ll get to it - and try to change the speeds from 100Mhz to 133Mhz. It should be in the "CPU frequency" option from that page you mentioned. Try changing the settings to 133Mhz...
  6. Before I do that, let me run this past you! I found that Sandra software, (and quite a tool it is!). One of the things it has noticed is that although the CPU temperature is low, (30C), the mainboard temperature it is saying is too high, (77C).

    Presumably, if I increase the speed of the processor, it will generate more heat.

    Could this high mb Temp be throttling the CPU?

    If the CPU is running at 30C is it possible it could be heating the mb to 77C? Could the reading in Sandra be wrong? Could one of the "xbridge" chips be heating it, (they have big heatsinks but no fans)?

    What do you think?

    Med venlig hilsen,
  7. Hm, yes, P4s all have rather interesting thermal protection in that they do indeed throttle down...

    But I don´t think that´s what is happening. The CPU would only throttle down if <i>its</i> temperature were too high! And its 30C is extremely cool for a CPU, and is of no concern. Howevever, 77C is high indeed for the mobo. An increase to a 133Mhz-clocked bus should increase overall temperature... So maybe - and I haven´t heard about this ever happening! - your chipset is throttling the FSB... :tongue: I wouldn´t bet on it, though... Anyone out there with an idea?

    It sounds strange, still... the x-bridges aren´t supposed to generate that much heat, hence only heatsinks... If you leave your case open, the temperature should drop. See if that makes any difference, and check for good airflow inside the case or something... And check the BIOS setup anyway, it should contain a Hardware monitor that´ll tell you the temperatures as well... Look for the CPU frequency in there too.
  8. I don't know if you noticed, I edited in the CPU frequency in an earlier message, and yes, it says 100MHz, so that looks like a good spot. The BIOS temperature monitor says 37C CPU and 31C System Temperature.

    Do you know where/how the mb temperature is measured?

    Med venlig hilsen,
    adrianxw<P ID="edit"><FONT SIZE=-1><EM>Edited by adrianxw on 03/20/03 09:31 PM.</EM></FONT></P>
  9. Oh, I hadn´t noticed that you edited your earlier post... Sorry :smile:

    Hm, so there is no 77C on the Hardware monitor on the BIOS setup? That´s strange... Might be that Sandra is reading incorrectly...

    Have you tried looking at the options of the two fields you can tab to on the BIOS setup? The CPU ratio is 19 and should be locked, I think, and is not important for the FSB problem. See if you can change CPU/DRAM speed... look at the options...

    As to how temperatures are measured, I think there are temperature sensors (electrical ones) on specific spots on the mobo. The "system" one is probably on a main location on the mobo, and CPU should be referring to a sensor next to - guess what! - the processor. These sensors have electrical properties that are sensitive to their environment´s temperature. Because of that, measuring their electrical properties, which is easy and is done automatically in real-time, is a good way of getting an idea of the temperature they´re in. (just in case you wanted to know...)
  10. >>> I hadn´t noticed that you edited your earlier post

    Looking at the times, I may have edited it just after you posted and it is I that had not noticed your post!

    Anyway, I shut the thing down again and in the BIOS the CPU Ratio will let me tab to it, but won't let me change it.

    The other, CPU/DRAM Speed allows the following options...

    100/100 <- as now

    "Sandra" is still complaining about the heat!

    Med venlig hilsen,
  11. yours should be at:

    133/133 or
    133/166 (because yougot 2700 ram)

    133/133 woudl proababy be faster tho, keeping your fsb and memory in sync
  12. Are you unconcerned about "Sandra's" worries?

    The machine is working fine, so I don't want to fry anything, but at the same time, I paid extra to get the fastest they had available so I'd like to use that if I can.

    Med venlig hilsen,
  13. Well, that´s exactly what you need to go to 533Mhz: change to 133Mhz/166Mhz. That´s what it should be. You might try 133/133 or 133/100 just for testing, though...

    As for Sandra´s worries, well, it´s somewhat unusual that you mobo´s hardware monitor doesn´t complain at all. I have to say, I´d trust the BIOS setup more than I´d trust SiSoft Sandra. If you don´t cold boot - just reset your computer without turning it off - then are the temperature readings still 30-35C on the hardware monitor?...

    I think it might just be the case Sandra´s is reading incorrectly, if the Hardware monitor doesn´t see any problem. They factor in some "corrections" to the temps the BIOS reads. If I were you, I´d try changing to 133/100, see the (awesome) boost in performance, and check temperatures again - in Sandra and in the BIOS setup. I really don´t think that should fry anything. And you could get an idea of temperature increase...

    As for what phial said, keeping fsb and memory clocks synchronous, that should offer good performance. I don´t know, honestly, if sync 133 is better than 133/166... But you can try that out later on...
  14. Okay guys, I'm going to try setting to 133/133, (I can't have 133/100), run it fr a while then check the BIOS Temperature, if okay, I'll try 133/166 and do the same. If both look safe, I'll run some of the benchmark software in Sandra and see which seems to be best.

    I'll post a little follow up later, if I don't You'll know I fried!

    Med venlig hilsen,
  15. Well, still here. The old performance test I used, http://download.com.com/3000-2086-10160270.html?tag=lst-0-9 gave me a score of 173/404.7 MFlops at 100/100. At 133/133 it gives 217/534.4 MFlops, and at 133/166 221/545.8 MFlops.

    The BIOS temperatures seem unchanged. Sandra still shows the mb Temp as 77C - unchanged, BUT, she sees the PSU temperature has risen from 38C to 47C, reporting the CPU still at 30C. I'm guessing the value she is seeing for "PSU" is actually the CPU, and the "CPU" is actually the system temp.

    Whatever, I'm running at 133/166 right now and will leave it like this for a soak.

    Thanks for the input, I've learnt a good deal, (of course, I now have more questions than before!).

    Med venlig hilsen,
  16. Glad to hear you made it through! :smile:

    I told you SiSoft Sandra wasn´t that reliable! And your guess seems quite reasonable, if you ask me. It only makes me wonder where the hell Sandra got the 77C from... I wouldn´t worry if I were you.

    If you do still have questions, ask them, someone around is bound to have an answer. It´s the right place to ask. And have fun with your <i>truly</i> 2.53Ghz P4!
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