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Abit AN7 mainboard is unstable when CPU multiplier is set to 11.5x

By Nic
Feb 7, 2004
  1. I recently puchased an Abit AN7 mainboard, then after finding a problem, I had it replaced, and found the same problem again. Here is what I found ...

    The Problem
    ===========
    The Abit AN7 mainboard is unstable when CPU multiplier is set to 11.5x (and *possibly* when set higher also) and overclocking features are enabled in the bios. This instability exists even when you do not overclock, but simply enable overclocking in the bios. The instability is worse when you do overclock, but either way, you can expect random lockups and freezing within minutes of power-on. Clock multiplier settings of 11.0x and lower do not appear to suffer from this issue.

    This is problem is obviously a very real issue when running an Athlon XP Barton 2600+, as these chips are factory locked at 11.5x multiplier setting. Enabling the overclocking features is therefore not advisable on these chips, though it may be possible on chips with higher multiplier settings (I have not verified this as I only have 2500+ and 2600+ chips with which I can test).

    Testing
    =======
    1. My previous Abit AN7 mainboard, which I returned suffered from this issue, as the CPU I installed was a *locked* Athlon XP Barton 2600+. I later returned this mainboard for replacement believing it to be faulty.

    2. On receipt of my replacement Abit AN7 mainboard, I installed an *unlocked* Athlon XP Barton 2500+, which I borrowed from my Abit NF7-S v2.0 computer. This chip I had been running successfully on my NF7-S v2.0 with any multiplier up to 12x on this mainboard. However, on the AN7 I found that the chip was only stable up to 11.0x multiplier setting, and when I went up to 11.5x setting I encountered random lock-ups and freezes, much as when I had the *locked* 2600+ cpu installed on the previous mainboard (that I returned).

    3. I decided to fit my original *locked* Athlon XP Barton 2600+ back on this mainboard. It can only be run with a multiplier setting of 11.5x as it is factory locked by AMD. I now found that I am getting random lock-ups much as before, simply by enabling the overclocking features in the bios, and even when no overclocking is taking place.

    Summary
    =======
    The Abit AN7 mainboard seems to have a bug that is apparent only when running CPU's with 11.5x multiplier setting (possibly for higher settings also - I cannot verify higher settings). When using an Athlon XP Barton 2600+ (which has factory locked multiplier of 11.5x) and when enabling overclocking features in the bios (even with no overclocking taking place) the system will become highly unstable and will lock-up randomly within a short time from booting. The mainboard appears to be of defective design, or there may be a bad batch of these mainboards in circulation. This I am unable to determine, as only Abit will be able to investigate fully.


    If anyone else here at TechSpot has come across this issue, then please post your findings here so that some idea of the extent of the problem can be reached. Thanks.

    Asides from this issue, I can say that I really like this mainboard a lot. Firstly you do not have the PCI slots covered by the usb/firewire bracket that the NF7-S v2.0 mainboard has, and there are a lot of nice features in the bios. I would happily buy another, but only if I could count on it working properly.

    A couple of other things that I am not impressed with are that the mounting point for the bottom right corner is too close to the IDE connector and so a very narrow screw has to be used if it is to fit this mounting point.

    Also, the fan monitoring utility does not allow for fan speeds lower than 2000 rpm, so my 1500 rpm 12 cm fans will trip the alarm when I run the Guru utility, and I then need to reload safe defaults in the bios before the alarm will stop. Then I have to go back and set my bios back to the way I like it, and remember not to run the Guru utility again. A few niggles, but still a nice board, if only it worked.
     
  2. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

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