DDR3 1600 Memory Speed Question

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?

Reply to bpdski
14 answers Last reply
More about ddr3 1600 memory speed question
  1. CPUID? Do you mean CPUZ? If not, you should really try that app and see what it says.
    Reply to Nils
  2. yeah, that's what I mean, I have the latest copy
    Reply to bpdski
  3. 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.
    Reply to Nils
  4. 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.
    Reply to bpdski
  5. maybe your MB downclocked the RAM?
    Reply to computernewbie
  6. 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
    Reply to Nils
  7. 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.
    Reply to bpdski
  8. 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.
    Reply to Nils
  9. That's right 800Mhz = DDR3 1600. Kind of confusing with all the different labels. I agree though, I think I have bad RAM.
    Reply to bpdski
  10. 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.
    Reply to Nils
  11. 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.
    Reply to bpdski
  12. I hope your problem will be solved then.

    So you on the forums!
    Reply to Nils
  13. 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.
    Reply to maelk
  14. From my understanding of ram ddr3 1600 reprezents data rate for data transfer not data clock witch by the way is a differential clk with 2 signals obviously one is clk_P (pozitive)
    and one is clk_N (negatvie) . And the most obvious question is why 1600 MT/s and not MB/s it is the data transfer rate not the clk. Well the answer for the big question is because the memory dimm splits in 2 chunks of 32 bit set of data lines lines witch together form 64bit data lane but then again it is about 2 sets running @ the same clk speed one set gives us 800 MT/sec and the other ads up beeing separate data lane. That means that a ddr3 dim will have @ least 64 data lanes noted from data1 pin to data 64 witch data is addressable by the address lane. Address lane number will all ways limit by the amount of ram memory and it's quiet easy to understand why one address will open 64 bits of data @ one clk cycle. That is to bee counted that other cycles may occur due to any other set of pins will light up. It is how actually data rate is calculated/s due to the fact that 800MHz is 800.000.000 cycles per second means that one cycle period of time would be 1/800.000.000 s
    Reply to soundblinder
Ask a new question Answer

Read More

Memory DDR3 Intel i7