Why is my PC6400 RAM at 400MHz?

[Newbie2]

Hello guys,

I'm wondering why is my PC6400 RAM only operating at 400MHz? I just overclocked my Pentium Dual-Core E2180 to 2.66GHz, and when I checked the operating frequency of my RAM it's 400MHz (its actually 399MHz, close enough) in CPU-Z.



Another forum has been telling me to put the ratio to 1:1. Will that overclock my RAM, and please give me a very good explanation to that, if yes or no.

Please tell me why my RAM is displayed at 400MHz?!

[mobo57]

Probably you have your memory settings in the BIOS set to Auto. The mobo will pick up the SPD settings from the memory chip and set the divider nearest to the rated speed of the memory.
As to the 400 speed, you have DDR memory, that is Double Data Rate. The 400 is one half of a full cycle, therefore double that and you have your memory speed, 800 mhz.
Yes setting your divider to 1:1 will over clock the memory. For absolute performance, keeping the divider at 1:1 is usually best. Problem is can your system handle the increase? Your memory would probably be hard pressed to handle your current 1064 FSB setting as that is a VERY significant increase, even with a major increase in VDIMM and relaxed timings, that is unless it is some really good top of the line binned stuff. And the reality is you will probably have to relax the timings to the point where any gain in FSB will be offset by the increased timings and loss in stability. You can find out for your self what the change in speeds will give you. Set your FSB to 200 and divider at 1:1 then benchmark. Next change the divider to 3:2 and bench again. I'd bet you may get maybe 3 to 5% at best.

[BipolarBill]

Doesn't the Intel CPU use quad rate RAM? If so, he's actually running at 1194MHz.

399MHz is the actual frequency - not the effective FSB. You need to look in BIOS setup to see the effective rate.

[mobo57]

Good point BPB, I should have explained that a little better. It runs at 4x the bus speed.
Need to add though after looking at the current timings, I doubt much more is available out of those chips. 18-5-5-5 on PC6400 is real loose if that is the SPD settings. I have 8 gigs in my system of 6400 running at rated speed at 10-4-4-4, SPD is 12-5-5-5.

[BipolarBill]

So its fine then.