Core i7 920 and DDR-1333 memory

No, without OC the i7 runs at 1066. See here: http://www.intel.com/support/proce [...] 029913.htm

Most mobos let you independently adjust the memory multiplier. The base clock frequency is 133MHz. 1066MHz / 133MHz = 8.
1333/133 = 10. So to effectively use your memory, you need to go into the BIOS and change the memory multiplier from 8 to 10.

Or you could try increasing the base clock until the memory multiplier becomes 10 but you didn't want to over clock .....

Take a look here:

http://www.computerpoweruser.com/e [...] F24c03.asp

Mike

Siminlal,
Please read the two links that I provided. From the first,
"What is the maximum frequency for DDR3 memory when used with Intel® Core™ i7 desktop processors?

These processors support DDR3 memory with a maximum frequency of 1066 MHz. If faster DDR3 memory is used (such as 1333 MHz or 1600 MHz), it will be down-clocked to operate at 1066 MHz."

The SPD is used to make sure that memory slower than 1066 is read at the correct number of cycles. But the adjustment upwards stops at 1066. So by default, if your memory supports it, the speed is 1066.

Summing up, the CPU will down clock your memory but will not up clock it past 1066. For that, you need to tinker with the BIOS.

Hence the 2nd link.

Really, read the links.

Mike

Thanks again, Mike. I did have a look at the links - unfortunately the ComputerPowerUser site tells me I need to be paid subscriber to see the article you linked to. Not to worry, though - you've told me what I needed to hear.

Thanks, geofelt! Sounds like I don't have anything to worry about.

Depending on how the memory is programmed...

Depending on how the MEMORY is programmed...

Depending on how the MEMORY, not the processor, is programmed...

It could fire up and operate at DDR3-1333. That's because Asus BIOS is smart enough to know this stuff. Intel "rates" some processors at 1066 and others at 1333 max, but Asus knows they can all run 1333.

Thanks Crashman! So I take this to mean that even though Intel says that the processor caps the speed at 1066, that may only apply to the initialization of the processor by itself - once the processor has completed it's own powerup sequence the motherboard can come along and apply it's own values. All of which makes perfect sense, otherwise overclocking wouldn't be possible.

I've looked in the Asus motherboard manuals, and the closest I can find to information on this subject is in the "Tweaker Menu" section under "DRAM Frequency". Here it lists some of the options, including "Auto" - but unfortunately it doesn't say what "Auto" actually does - whether it sets the memory's SPD-defined speed or just leaves the speed set by the CPU (which for the Core i7 920 would be 1066) without changing it.

That's interesting - I learn something more with each post. It looks like XMP is just another level of SPD information on the DIMMs, which still begs the question of what the motherboard will do with it. The Asus motherboard manual says that it "supports XMP", but then it doesn't actually refer to "XMP" anywhere in the manual aside from listing support for specific XMP-enabled DIMMs.

Perhaps an example can help. With a P6T deluxe, I changed the BCLK from 133 to 160 giving 3.2. Everything else was left to default or auto.
My ram is patriot 1600.
In cpu-Z under SPD it shows XMP-1600 800mhz, 9.0-9-24-38-2T and 1.65 volts. That is the max for the ram.
Also under spd there are two jedc#
457mhz,6.0-6-6-18-24 -1.5v
533 mhz, 7.0-7-7-20-27-1.5v
---------------------------------------------
the result under memory, which is what is actually running:
dram frequency=480.0
fsb to dram 2:6 I think this means that my ram is operating at 1440, somewhat below it's maximum.
cas 4.0 clocks
ras to cas delay 6 clocks
ras precharge 6 clocks
cycle time 18 clocks
command rate 1T

As I recall, the result voltage is also 1.5