gonX

QDR means Quad Data Rate, so like DDR (Double Data Rate), it sends quadruple (as opposed to DDR's twice) as much data per MHz.

So basically, a FSB of 400, will result in a QDR of 1600.

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GigaByte

Most likely the NB causing it, stay at those volts as they are low and safe then try 3.60GHz. As gonX said FSB in it's quad pumped state (QDR) is the bus speed 4x, 400 x 4 = 1600 QDR, 500 x 4 = 2000 QDR and so on.

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ned99

I can't get anything stable lower than vcore 1.256v and vtt 1.30v. I've got both the nForce SPP and the NF200 voltage levels set at "auto" would changing them make any difference? I've also got my memory clock mode running as "unlinked" if that makes a difference as well. Thank you for your help as from reading other threads about q9550s it seems like a vtt of 1.30v for a 3.4 ghz overclock is high.

Thanks for explaining about the QDR, so simple but I could find the answer anywhere.

Sorry one more question, which controls the voltage for the northbridge: the NF200 or the nForce SPP?

GigaByte

SPP is your northbridge, it is also the memory controller and is what generates the FSB speeds. Increasing the voltage to that will probably help in stability especially with a quad core and/or 4x1GB RAM. Add at least 0.10v to the SPP then try lowering the volts for 3.40GHz or try for 3.70GHz again.

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ned99

Adding the 0.10v to the NB seems to have helped (it's now at 1.50v) Prime95 is running stable at vcore 1.25v and vtt of 1.20v at 3.4 ghz. Should I pay any attention to the BIOS labeling of temps grey/green/red? I checked the intel site for the voltage limit of the q9550 (1.3625) but what is the top limit of the vtt and the SPP? Thanks again for all the help, obviously this is my first shot at overclocking and I'm scared and confused