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Dual Channel Issues with promising CPU/Mobo combo

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System spec:-

CPU 3GhzE 1Mb cache

Max FSB250Mhz 3.75Ghz

SL7E4 Prescott Stepping 4

Revision D0

water cooled



Abit IS7-E

Model 1.0 Rev A2

Bios 2.4



2x512mb Corsair XMS4000Pro



ATI Radeon X800XT 256mb

GPU watercooled



ALR 7200 Server case

2x120mm fans


Cooling Custom tap feed water cooling system

Cooling CPU and GPU

60mm fan on Mobo Mosfets



Picked this 3Ghz Prescott up a couple of months ago and just got an Abit IS7 with some 2X512Mb Corsair XMS4000Pro 500Mhz RAM ( the ones with the LEDs and huge black heat spreader )

I am quite experienced with PC hardware and overclocking as i have been into the scene as long as its existed ( just so you know am not a clueless Noob )


I chose DDR4000 so i would have good overhead for overclocking and initially things have gone very well. Been able to push the CPU upto FSB250Mhz 3.750Ghz without any CPU issues at all and with voltage at 1.38v.


However everything is super stable at that speed, but when i played any games that are quite demanding, i was getting artifacts displaying similar to what happens when you push a G-card too hard.

Now i know this issue was not my G-card cause its rock solid at its current settings, but i did disable my g-card overclock just to test, the artifacts where still there.

A quick FSB reduction to FSB233Mhz showed that the artifact issue was gone, I then tried my system at FSB250Mhz again but with a 4:5 DRR multiplier which set my RAM at 200Mhz, from doing this i discovered my RAM/Mobo combo do not like FSB/DDR to be non synchronous as it resulted in several crashes.


By the way for those who are by now assuming my RAM is FUBARed, my memory itself is in perfect functional condition as i have Memtest86ed it over night several times with no errors at all. My Ram is also set to its recommended timings.


So i then set out to track the prob exactly, i assumed it was some kind of config issue or maybe bad RAM, so i ran my system with each stick on its own and both sticks went to FSB250Mhz without any artifacts in games.


I then tried running with both sticks in single rather than dual channel DDR configuration, at FSB250Mhz games ran without any artifacts, as soon as i changed back to Dual mode, the artifacts where back.


So as you can see my problem is that running dual mode at FSB233Mhz+ causes artifacts in RAM rated for 250Mhz, yeah i can run at FSB233Mhz or run FSB250Mhz+ in single mode, but the performance hit in single mode is significant, and am a bit pissed that RAM rated for FSB250Mhz will only do it in single channel mode.

Am not enormously experienced with DDR RAM systems as i have only just moved over from RAMBUS.


Has anyone had this prob themselves or know anything about it?

Is this kind of dual channel issue when overclocking hard common?

Does anyone know any workarounds or fixes?

Anyone know if it could be an ATI driver issue?


Am considering buying different RAM but would like to keep the RAM i have if possible.


Having felt out my new system am convinced that my CPU has got quite long legs am confident it will top 4Ghz but with the dual channel issue am not sure am not too motivated to go for it.


Any help or advice on this issue greatly appreciated

Thanks Zeb

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