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Thread: Some questions about cpu and memory frequencies...

  1. #1
    Join Date
    Sep 2003
    Chicago, IL

    Default Some questions about cpu and memory frequencies...

    I just put my new machine together last week and have it running. I've got a EVGA mobo (680i), E6600, and 8800GTX card, with super talent 6400 DDR2 RAM. I see that the cpu is running at 1066 and the ram is running at 800. Obviously, this is decreasing performance. I don't know If I can overclock the ram to match 1066, but I am looking for a guide / explanation on all this type of stuff. The bios for my new mobo is much more complicated than what I am used to (I had a IC-7 MAX 3). I just find myself kind of lost in all this and haven't even started messing around with any of the settings yet.


  2. #2
    Join Date
    Jan 2003

    Default Re: Some questions about cpu and memory frequencies...

    Hey FroGGer, before I answer your question, I'd like to explain a little about FSB an CPU, to see whether you need to overclock your computer memory or not. In Computer to get any work done, data (in the form of electrical signal) has to get from memory to the CPU and vice versa. The bus is like road, and signal is like car. The wider the road (higher bus) allows more signal to travel at a given time; however, there is one catch all of these bus(es), is that they have speed limit. For example, PCI bus is running at only 33Mhz, and AGP is running at 66Mhz, twice the speed of the a PCI bus. The CPU you said runs at 1066Mhz, but in reality it doesn't run 1066Mhz. The reason intel can claim their CPU to run at 1066Mhz is because the CPU is being enhanced to what is known as Quad-Pumped (QDR)
    The CPU bus is only at 266Mhz, but since it has been enhanced to QDR
    we simply saw that 266 * 4 = 1066Mhz as the bus speed. What this means is that Intel has enhanced their CPU to handle 4 signals per cycle. So when you overclock your RAM you're just overclocking the actual speed at which the RAM runs to send its signal to the CPU.

    I'd like to present a little analogy. For example I have a 4 lanes highway, and I set the speed limit to 80mph. Now say, bunch of cars is driving on my highway, but those cars max speed is only 66mph, they couldn't go the full speed of the limit even if they wanted to, and thus the bottleneck is the car not the road. Now, let's look at another scenerio. Say a bunch of Ferrarri is driving on my highway, and those cars' max speed is 222mph, we can cleary see that even if those Ferrarri wanted to go their full speed, they can't because it violates the speed limit. Sometimes, some people are mistaken about bus speed. They think that if they buy really fast memory or overclock their memory it will solve their problem. They forgot that that the memory speed that they buy needs to be supported by their system bus speed also.
    Say, for some magical reason you can overclock your memory speed to 10000Mhz but your system bus only supports 800Mhz, then it's no use. In this case, we have a situation similar to the Ferrarri on a low speed limit highway.

    Now with all that said, here is the recommended settings between ram speed and bus speed:
    As far as matching FSB to DDR2 speed my recommendations as follows

    800MHz FSB = DDR2 533MHz ( ideal ) or DDR2 400MHz (matched, but slow) 1066MHz FSB = DDR2 667 ( good ) or DDR2 533MHz ( matched )

    However in your case, your said you are running:
    FoGGER -> "talent 6400 DDR2 RAM. I see that the cpu is running at 1066 and the ram is running at 800". Seems to me like you need to overclock your system bus not your RAM bus.

    266Mhz * 4 = 1066Mhz (4 signal per cycle because of Quad-Pumped).
    533Mhz * 2 - 1066Mhz (because your RAM is DDR, it send 2 signals per cycle).

    Your current memory is running at 800Mhz * 2(DDR) = 1600mhz, that means it would take a CPU bus of 400Mhz * 4(Quad-Pumped) = 1600Mhz to match the speed at which your RAM sends signal. So the answer is that you don't need to overclock your RAM anymore. Your RAM speed to CPU bus speed is good. What you need to increase is your system bus speed. How you will do that I can't really help you with because I don't have your motherboard, BIOS are different from each other, I don't know what to adjust on your BIOS to make that change; however, I hope that you have a better understand of system bus (FSB) speed and RAM speed. Just because you increase your RAM speed that doesn't means automatic increase in performance. Everything has to balance out for the maximum performance. Then there is also Multiplier to take into account for too, but I don't want to take about that, or this will becomes an essay. Good luck
    Last edited by Lone7; 01-20-2007 at 07:22 AM.

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