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PCIE freq and BIOS options

Discussion in 'Graphics Cards' started by imperialreign, Oct 28, 2007.

  1. imperialreign

    imperialreign New Member

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    Well, as some might remember, I was testing out various settings for PCIE frequency and the ASUS PEG Link controls . . . well, with my recent system failure, I lost al the accumulated info I had gained for my X1950 PRO. So, I will post up what I remember . . .

    I still haven't gotten to testing out my X1300 512MB and my X700 PRO yet, so I guess they will be up next cause I'm not in the mood to go back through everything with the 1950.

    This is just to try and throw some things out there that might possibly help others, seeing as how there's not much info on PCIE BIOS controls on the i-net. Still, though, for best performance, you'll prob need to do some experimenting by yourself . . .

    i975x chipset system

    PCIE Frequency - through testing I had noticed that the PCIE freq directly changes the PCIE BUS speed (read through SYStool). I had also noticed, that the higher you jack your system BUS, it directly affects the PCIE BUS. It seemed that the higher you take the BUS, the more it would lower the PCIE BUS for a given frequency setting - i.e. at 165 BUS with PCIE freq set at 115, the PCIE BUS would be 86.~, but if I took the BUS to 175, the PCIE BUS would be 45, which would require me to take the freq up higher to have the same PCIE BUS as at 165 BUS. I get the feeling that the seeing as how the PCIE x16 slots on my board are controlled by the NSB, that the 975x chipset is the biggest speed bump here.
    Anyhow, almot all freq settings showed the same performance level, except for a freq of 100, which seemed to drop performance quite a bit.

    ASUS PEG Link Controls:

    PEG Buffer - options are [AUTO][SHORT][LONG]. haveing the buffer set to [SHORT] showed similar performance scores in 3m06 no matter what the freq setting. [LONG] showed that there was quite a performance drop, though, an average of 200 3m06 marks for all freq settings. [AUTO] showed the best performance, though . . . more than likely because it allows the mobo to adjust the slot buffer as needed during operation, instead of locking it in to one specific length. Although, depending on system, locing the buffer into one mode might prove a better idea. Default for my x16 slots is short.

    PEG Latency - options of [AUTO][SLOW][NORMAL]. Again, [AUTO] seems to be the best setting for this card, with similar 3m06 scores. [SLOW] would drop scores a ton, and [NORMAL] provided a near unnoitceable performance hit.

    PEG Link Control - [AUTO][ENABLE][DISABLE] - turns on/off the BIOS PEG controls (i.e. if set to [DISABLE], it seems to turn all the PEG controls to [AUTO] or off, effectively, no matter what you currently have them set at)

    PEG Link Mode - [AUTO][SLOW][NORMAL][FAST][FASTER] - there was no change in performance for any setting. From what info I could find online, this option seems to allow the BIOS to automatically OC the PCIE card itself, but I noticed no change at all for the 1950 - so, either ASUS doesn't have a profile for the 1950 yet, or there's no need for the BIOS to OC the card. I'm interested to see how this effects my other two Radeons.

    Slot Power - [AUTO][LIGHT][NORMAL][HEAVY][HEAVIER] - I'm guessing that this adjusts power to the PCIE slot itself, but I have no way of testing that and I couldn't find any software that can read the slot voltage. I didn't notice any performance difference at all - perhaps this has more of an effect on a higher OC or higher BUS system.


    For what it's worth, at least on my setup, leaving everything to [AUTO], with PEG Link Control set to [ENABLE] and PCIE Slot Frequency at [115] seems to offer the best performance.

    After I get my rig back up and stable again, I'll get around to testing out my other two cards and see how these controls effect them.

    Any comments, thoughts people? Has anyone else gone to the extent of messing around with these controls and testing them out? I'm really curious to see what results others might be getting.
    Kursah says thanks.
  2. pphx459 New Member

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    Nice read..

    The issue I'm having is with this new Diamond 1gig HD2900xt card I have. It can run BF2142 all day and night in Vista but it will crash constantly (freezing + artifacts) while playing COD4. So just last night, I decided to run Orthos and multiple instances of memtest. It has been over 24 hours with no errors detected so I know the system itself is ok.

    Now, I'm lead to believe that it definitely has something to do with the video card. My card by default comes overclocked a bit. I never bothered to check the PEG settings in the bios as I didn't have any problems with the default PEG settings on my 1gig 1950xtx while I was on XP.

    I'm gonna try changing PEG link control to SLOW to see if my situation improves..

    I'm curious what are your PEG settings now, and what bios / drivers are you using? Also, what is wrong with your system?
    Last edited: Nov 8, 2007
  3. imperialreign

    imperialreign New Member

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    oh, nothing has ever been wrong with my system in regards to the GPU or the PEG controls . . . I just wanted to try to investigate the various BIOS settings further because there didn't seem to be that much information on the internet, and ASUS' owner's manual doesn't really offer good explanations of the PEG settings, either. Plus, what info you can find on the internet, seems to be conflicting, and no one has any concrete evidence to back up their claim.


    Anyhow, it was all about trying to push my 1950 PRO as hard as I can with a P4, at least until I can afford a new CPU.

    As of now, all my settings are at [AUTO], except for PCIE Frequency being set at [115].

    If setting PEG Link Control to [SLOW] works with your 2900XT, I'd be very interested to hear about that, and what clock settings the mobo BIOS sets, too.

    Here's some more reading from an earlier thread where I posted some results of testing just the PCIE Slot Frequency without messing with the PEG Controls: http://forums.techpowerup.com/showpost.php?p=492686&postcount=39

    Sometime in the next week or two, I'm going to throw my X700 PRO in this rig and see how the PEG controls affect it, then I'm going to test my X1300 also.
  4. pphx459 New Member

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    Oh I see, I totally agree with you. The info I found on the net regarding these settings are definitely conflicting. Some say set things on AUTO while others say use Normal instead.

    Anyhow, a quick update. I just played cod4 for over an hour and no more freezes!! (I can't claim victory yet but I'm pretty sure it's resolved.) At the moment, I have PGE Control set to SLOW and everything else AUTO. I think what really did it is setting the card back to it's default speeds. I had to use RivaTuner to underclock the factory default of 825/1100. Right now, I'm doing the ghetto way of powering the card, using 2x6pins instead of the 8pin. I think if I plug in the 8pin then I should be able to run the card at those speeds..

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