Memory help please

Hi I have been researching which memory type to buy because I wish to purchase a new computer. However I want to go in detail of the different frequencies.

I ask because I was hoping to buy a computer with Intel Core 2 Duo Q9550 (2.66GHz) 1333MHz FSB and have the
option to buy either 1,333MHz or 1,600MHz RAM. I was thinking to buy 1,333MHz RAM because it matched the FSB of the processor. I was reading about FSB ratios or something and I did not understand it fully so I looked at my current PC's RAM via CPU-Z and that confused me further about the Bus Speed, Rated Speed and DRAM frequency - they are all different! Also the 'clocks' is it better to have them all generally lower?Thanks.
7 answers Last reply
More about memory please
  1. Short version - ram will run at half the cpu's fsb. Take that cpu for example:

    http://processorfinder.intel.com/Details.aspx?sSpec=SLAWQ

    FSB is 1333mhz / 2 = 666.5 or 667mhz

    Long version:

    http://en.wikipedia.org/wiki/DDR2_SDRAM

    If you don't overclock, pick up any 800mhz ram.
  2. RAM runs at 1/2 the speed of the FSB. Basically, ram speed is x2, and the fsb is x4.

    Get DDR2 800mhz ram. In order for the ratio to be 1:1 (best for overclocking), you would need to set the fsb to 400mhz, then both the ram and fsb will be running at 400mhz. If you buying anything faster than 800mhz ram, it will bottleneck the cpu unless you underclock the ram.

    Sorry if that's confusing. Post back any questions you have.
  3. Thanks for both replies.
    br3nd064 - thanks for that.

    But if it is half could I use 667MHz RAM or am I missing the plot :pt1cable: ?

    This computer place I am buying from only sells DDR3 1333 RAM (more specificaly "CORSAIR XMS3 DDR3 1333MHz") with "ASUS STRIKER II EXTREME" motherboard. The reason why I want this motherboard is because I intend to upgrade the CPU and GPU in time in the future.
  4. Use 667mhz ram if you don't intend to overclock. Use 800mhz if you want to do any sort of overclocking with the q9550. I suggest getting a motherboard (maybe from an online retailer) that supports DDR2 ram until DDR3 becomes more mainstream and affordable. Although DDR3 runs at higher frequencies, the timings are horrible, and until they lower the timings, IMO, it's not worth it.
  5. Oh I see :) thanks for your help.

    Is there any need for 1,600MHz RAM and above right now because the fastest I assume (for CPU) is 1600/2 =800!

    Sorry but you know when you say 'timings' is that the same thing as latency and cycles? Is it better to have it less?

    Thanks again!
  6. Faster ram is for overclockers. Just like Extreme C2D/C2Q chips. They're $1000+ apiece. For the average user, they don't need them to run a pc.

    Less timings/latencies are faster and more expensive. You won't notice a difference if you don't overclock.
  7. No, there really isn't any need for 1600mhz ram. It would be bottle-necking your cpu a lot.

    Yes, "timings" are the same thing as latency. Basically, the timings are the number of cycles it takes before the ram starts responding to a request. Good DDR2 ram runs at 4-4-4-12 stock. The *best* DDR3 runs at ~6-6-6-18, but they can go all the way up to 9-9-9-20 or more.

    Summary: Try to get some DDR2 ram at 4-4-4-12 with low voltages.
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