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DDR3 1600 Memory Speed Question

Last response: in Memory
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August 5, 2009 12:21:15 PM

I have an i7 920 system and purchased DDR3 1600 (PC3 12800) memory for it. When I run cpuid, it shows a memory speed of 400 Mhz under the memory tab which I think sounds right. However, under the SPD tab it says the memory is PC3-8500F (533 Mhz). Also, it says this in the BIOS as well and if I try to set the memory any higher such as the 1600 it is supposed to be, it won't boot. Can someone help me understand what is going on here? Why does cpuid not say that I have PC3 12800 memory?

Thanks
August 5, 2009 2:01:22 PM

CPUID? Do you mean CPUZ? If not, you should really try that app and see what it says.
August 5, 2009 3:12:09 PM

yeah, that's what I mean, I have the latest copy
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August 5, 2009 3:41:14 PM

Then you are running the ram @800mhz now instead of 1600mhz. CPU-Z always displays the real memory clock which you have to multiply by 2 because it is DDR RAM.

So the highest SPD profile is for 533mhz (1066 mhz effective)? If so, are you sure you really bought DDR3 1600 and not DDR3 1066? If you can open your case you might be able to check any labels pasted on the dimms. These normally report actual ram speed.
August 5, 2009 5:14:53 PM

Yeah, the sticker on the memory says OCZ3P1600LV6GK and CPUZ reports OCZ3P1600LV2G as the part number. This is supposed to be DDR3 1600, I wonder if the memory was incorrectly labeled. There are heat spreaders glued to the chips so I can't actually see the part number of the chips.
August 5, 2009 7:07:13 PM

maybe your MB downclocked the RAM?
August 5, 2009 7:38:52 PM

Quote:
maybe your MB downclocked the RAM?


Even if it is downclocked, you should be able to crank up the speed to 1600 and run it without errors if it is true ddr3 1600 ram.
I guess right now you speed up the RAM by increasing the memory multiplier? Can you try to get it to 1600 just by increasing the baseclock. To keep your cpu at the same level you can lower the CPU multiplier. Give that a try
August 6, 2009 11:45:15 AM

It looks like I can control the memory multiplier from x3 - x8. When I set the base clock at it's default of 133, I can then set the memory multiplier to x6 and boot the machine with the memory at 1600. However, I'm also able to set the base clock up to 180 and run the cpu very stable at 3.6Ghz. In fact, it's been running that way for several days with world grid software cranking on it with no problems. At a base clock of 180 though, I can't set the memory multiplier any higher than x3 (540 MHz). If I set it at x4 (720 Mhz) the system won't boot. Any idea why I can run it at 1600 with a 133 base clock, but no higher than 1080 with a 180 base clock?

In every case, cpuz always reports the memory type as PC3-8500F.
August 6, 2009 1:12:27 PM

At a base clock of 133 and a memory multiplier of x6, the memory should run @800mhz. With a MP of x8, it will run @1066mhz, which is the maximum speed reported by CPU-Z. I think there is a good change your RAM is wrong labeled.
August 6, 2009 3:49:57 PM

That's right 800Mhz = DDR3 1600. Kind of confusing with all the different labels. I agree though, I think I have bad RAM.
August 6, 2009 5:47:39 PM

No. 800Mhz = DDR3 800. Check out this page: http://techgage.com/article/gigabyte_ex58-ud5/2

Here they review the Gigabyte X58-UD5 board and they use RAM made to run @1333Mhz. To get it running at that speed they use a x10 memory multiplier with a 133mhz bclk. 10x133=1333mhz on the RAM. If your way of thinking would be correct, the ram would run at 2666 mhz! Take a look at the first picture on the page I linked for details.
August 6, 2009 6:56:11 PM

What I'm talking about is that in my BIOS setup it shows this:
2048MB/540Mhz (DDR3 1080). The 1080 is the "effective" speed.

When I set the base clock to 133, I'm able to get 800Mhz (DDR3 1600). When I crank the base clock up to 180 I'm only able to run 540Mhz on the memory.

I've RMA'd the memory, hopefully the replacement will work right.
August 6, 2009 7:01:52 PM

I hope your problem will be solved then.

So you on the forums!
August 23, 2009 7:56:48 PM

I have the OCZ3P1600LV6GK and CPU-Z reports OCZ3P1600LV2G just like you've experienced.

I cranked up the multiplier and the RAM is so far running fine at 1600MHz. It was running at 1066MHz before.

It's the 3x2gb kit on a Gigabyte EX58-UD4P board.
!