Synchronous or asynchronous mode

Hi everyone.

I have been reading and learning from the forums here for a long time but this is my first time posting. I am just starting on my first build:

Asus P5QL pro
Intel E6300 2.8 1066 45nm
OCZ platinum 4x1gb sticks DDR2 pc6400
WD 500 gb blue caviar
Freezer 7 pro HSF
Coolermaster 330 Elite with 460 watt PSU + 120mm front fan + 80mm sidecase fan
HD 4350 512mb

I know ir is best to run a system on synchronous mode. However, with my system, i think it'll be a far stretch overclocking my cpu from 266mhz to 400mhz. I am willing to overclock but not too much. As my RAM runs at 400mhz, underclocking it to 333mhz could probably be acompromise. Here are the questions:

1. Ist it possible to overclok the CPU and underclock the RAM?

2. If 1 is possible, would it be a better system that way or should i just overclock the cpu to 333mhz and leave the RAM at 400mhz.

Please correct me if i'm wrong here. My RAM, although it is a 400mhz will run at 266mhz because of my cpu. But this is still not a 1:1 ratio. How can I make it 1:1.

The system will be used for heavy photo editing and I want to try Crysis. The GPU will be upgraded to HD 4670 in a few months.

Thank you.

2 answers Last reply
More about synchronous asynchronous mode
  1. Sorry I'm a bit unfamiliar with clocking RAM, so I'd like to ask why would you want to underclock RAM? To better sync voltages with the FSB and the CPU?
  2. Arthan,

    Definition time (attention purists, I'm talking about DDR2 and I'm simplifying a little :)):
    Core2 CPU's use a frontside bus (FSB). The FSB is a thing with two main characteristics: speed which is usually defined in MHz and width which in the Core2's is 64 bits wide. We are concerned with the speed.

    Using the Q6600 as an example, the FSB frequency is 266 MHz. The matching DDR2 memory clock for that frequency is 533 MHz (266 X 2). DDR2 memory transfers two chunks of data for each bus cycle, hence double the frequency. So, to run 1:1 at an FSB of 266 MHz, we need DDR2-533 RAM. What CPUZ does is a little confusing. It will tell you that the memory frequency is 266 MHz for a 1:1 ratio and not the memory clock.

    The FSB clock is 1066 MHz (266 X 4). The bus is "quad pumped". It transfers 4 chunks of data into and out of the CPU each cycle. So each FSB cycle generates 4 FSB clocks.

    Now, if you increase the FSB frequency to 333 MHz, the corresponding memory clock is 667 MHz and the FSB clock is 1333 MHz.

    I always run my memory at 1:1. That is the FSB freq to mem freq ratio as defined by CPUZ. That means that the memclock is twice the FSB freq. It's a little confusing.

    Running memory slower costs performance. Running memory faster does not give you much if any real world performance increase and it can lead to higher instability.

    Technically, if you are running your RAM at a 1:1 ratio, regardless of bus speed, you are not overclocking or underclocking your RAM. You may be trying to run it faster that it was designed for, but you are not overclocking it.

    For overclocking your system, this should be your first stop:
    HOWTO: Overclock C2Q (Quads) and C2D (Duals) - Guide v1.6.1

    Next stop should be a guide for your particular motherboard. Google is your friend.

    Go through the guides. Then the first thing you should do is go into the BIOS and change the System Memory Multiplier from AUTO to 2.00, 2.00B, or 2.00D - whichever you need to set the Memory Clock to twice the FSB frequency. Then when you increase the FSB, the memory clock will always be twice the FSB frequency.

    Warning - confusion factor between what the BIOS calls things and what CPUZ calls things. What the BIOS calls "memory frequency" is usually the memory clock. What CPUZ calls "memory frequency" is half the memory clock - DDR2 RAM, remember? It transfers two chunks of data each bus cycle. What you want in CPUZ is a 1:1 FSB:RAM ratio.
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