Memory won't run at rated timings.

[viivo]

I have 3x2GB of Corsair XMS, rated at 1333, 7-7-7-20, 1.5v. Set by SPD and default voltage, it shows in CPUZ as 668MHz, 9-9-9-24. If I set the timings manually with default voltage, my PC doesn't boot, nor does it if I set the voltage to anything from 1.5 to 1.65 or use the "Extreme Memory Profile." Other hardware: i7 920, MSI X58M.

Memtest showed no errors, I'm not overclocking, and it's definitely not the PSU.

I get the feeling I'm missing something really simple here. I freely admit I haven't messed around with overclocking since the s478 Celeron, so I'm still trying to learn the purpose of all the X58/I7 BIOS options. Any suggestions?

 

[n7]

I found the 10x RAM ratio was rather hard to get stable when i had my i7 930x, & had to use the 8x one to OC.

In your case: 133 BCLK x8 = DDR3-1066 (10x =DDR3-1333)

Theoretically you should be able to do it @ stock, but it's not an Intel officially supported speed @ stock. (1066 is).

This post explains some of the complexities of X58 OCing.
http://www.xtremesystems.org/forums/showpost.php?p=3495431&postcount=877

Basically QPI/uncore have a huge effect, but for example in my case, even when i lowered the QPI & uncore speeds, i still couldn't get my system to POST using 10x RAM ratio when OCed even slightly; i had to use 8x.

In short, you may need to play around with some settings & voltages a bit, or run a lower speed.

DDR3-1333 is generally meant for use on an OCed X58, FWIW, not stock, regardless of what the memory manufacturers like to market.

Yellowbeard here is a Corsair rep; he might know some tricks for getting your RAM stable on that 10x ratio.

 

[viivo]

So it's to do with the 2:10 ratio? I guess that brings up the eternal question of which would be better: 1066 and tighter timings, or 1333 and whatever is stable.

Thanks, I'll play around with some settings.

 

[bryanl]

It's not unusual for manufacturers to change the specs in the SPD but not in their published literature, and I've seen such discrepancies with OCZ, PNY, and Corsair products. I have never gotten reliable operation at faster than the published timings, and most recently it took 10 hours of testing before the first errors were reported. This was no fluke but was repeatable. When the SPD timings were restored, the memory passed over 100 hours of testing.

 

[Scotteq]

So it's to do with the 2:10 ratio? I guess that brings up the eternal question of which would be better: 1066 and tighter timings, or 1333 and whatever is stable.

Thanks, I'll play around with some settings.

Unless you have some specialized app that thrives on getting the most bandwidth possible, I would recommend 1066 and tighter timings.

 

[viivo]

Unless you have some specialized app that thrives on getting the most bandwidth possible, I would recommend 1066 and tighter timings.

Well, I do a lot of video encoding and animations with 2+GB of image frames open at a time, though the former is mostly CPU, the latter I'm not sure if it's speed or timings.

At any rate it seems to run fine at 1066 7-7-7-20, and benches better than 1333 C9.

I did have one question. In my search to learn more about overclocking on the X58 I've read many guides, and the one thing that's never made clear is balancing the voltages between VTT, Vcore, QPI and VDRAM. One place says to keep VTT and DRAM within 0.3 of each other or you'll kill the memory controller on the CPU, others say 0.5, and yet others say it doesn't matter at all. Since my motherboard overvolts like a son of a bitch (set CPU to 1.1, shows in CPUZ as over 1.3, though it does stick at 0.998 when idle) I want to make sure I'm within the correct range.