If you OC your unmodified A7M266, please help!

[thetinkerer]

My A7M266 will OC using the FSB alone to about 143 completely stable, but becomes unstable around 144-145 (strange errors and benchmarks like 3DMark 2001 will lock up during the merry go round scene, but SiSoft Sandra tests run flawlessly) and won't load windows at 147-148. I am using Corsair PC2400, and have excellent cooling (CPU temps 45 idle and 50 load when OCd). I read many posts of folks who have increased the core voltage of the CPU to OC better, but if I move the VID (core voltage)jumpers from default (shown below), the machine won't boot or even post. My bios is 1003, 4-in-1 drivers are 4.24, and I have my mobo jumpers in the following positions:

JEN 2-3 (jumper free)

DSCKF all off (frequency selection dip switches) for jumper free

VID1-4 all in the 3-4 position as required by the manual for jumper free

VIO 3-4 (3.45 volts)

VIO1 1-2 (2.7 volts) I have also read on Mushkin's website
(I think) that they recommend removal of VIO1 jumper to make the voltage be 2.5, as they recommen, but others claim removing the jumper gets you 2.8?? In the 2.8 position, I get errors and program lockups.

Without changing any other jumpers, I tried moving the VID1-4 jumpers to 1.8/1.775 settings, from top to bottom:
VID4 1-2 VID3 1-2 VID2 1-2 VID1 2-3 (VID1 should be the one nearest to the lower edge of the board?)
but the machine will not even post. Moving them back to the default sets things back to normal. How are you OC folks changing voltage without disabling the jumper free options in bios? Is my bios 1003 restricted in some way? Has anyone been able to increase core voltage using bios 1003 like mine? Am I doing something else wrong?

If I move JEN to jumper mode, then all bios adjustments are disabled, and while I could theoretically (I haven't tried it) increase vcore voltage, my FSB would be limited to 133, the max allowed by the dip switches in jumper mode.

In the default mode, Sandra Reports the CPU voltage as 1.75.

The Athlon is an AXIA Y 1333
My power supply is a 400 watt sparkle
Running Win98
At 142FSB and the VisionTek GEForce 2 Ultra OCd to 275/500, my 3DMark2001 score is 4690, so everything seems OK.

The mobo is fast and stable, I just love to OC and tinker. As I have to leave town for a few days, I hope I supplied enough info for your appreciated replies (which I will read in about a week). Thanks

PS, I could, but don't want to, modify the board, so please limit advice to apply to an unmodified board

 

[Courtland]

The reason you cant get beyond that bus speed is most likely because one of your pci cards or components does not like running that far above spec speed. Try taking out all of your pci cards and see if you get better results, if you do then you can pinpoint the problematic component(s) via trial and error, and try to replace it with a better one. Might I add that the bus speed you can get it to isnt that bad, the 150ish area is pretty common. The best way for you to overclock more is to get a motherboard that supports multiplier adjustments or mod your a7m to do that.

 

[thetinkerer]

Thanks for the fast reply. Yeah I know, but when I read early reviews of the A7M before I ordered, the issue of the missing mult dips was not well known (and I am pretty sure I actually saw a picture of the board with the multiplier dips showing on the board-- I think I saw it on Tom's site). The only PCI cards I have are SoundBlaster Live Value (basic drivers only, no frills in PCI slot 3 with IRQ 5 assigned in bios) and a 3Com USR PCI Hardware voice modem. I tried removing the modem a while back, but no difference. I am reluctant to remove the SB card because they are such a pain in the @ss to set up and get stable.

 

[Courtland]

The live should be fine as far as runnign at a higher clock speed, its hard to say what it is. If the board ddr or agp voltage settings you could try those, or make your ram timing settins less agressive, although I doubt the memory is your problem. However, I don't know much about the corsair memory.

 

[Yozza]

It is probably the VCore that is limiting you in this case. You cannot change the multiplier on the A7M266, so your CPU could well be reaching its limit at the default voltage (1.75V)

You can possibly try increasing the VMem to 2.7V or even 2.9V to see if it helps.

Corsair XMS2400 uses Micron chips, so they should overclock better with more voltage, as Crucial's do.

I don't know why you are unable to set the VCore while in Jumper Free mode. I am currently running at 1.85V (actually 1.88V) with an FSB of 152MHz.

Make sure you are manipulating the jumpers correctly though.

Yoz