New Build RAM Choices....??

Hi all,
I've managed to get the missus to agree to a new PC.
I'm planning on a new motherboard, RAM and Processor.

Current System:
Asus A7N8X Deluxe
Athlon XP 2600+ (Barton Core I think)
2x512 + 1x256 PC2700 RAM
160Gb Excelstor SATA Drive
ATI Radeon 9800 Pro 256Mb
Vista Home Premium 32-bit
dual boot with XP Pro 32-bit

New System:
Asus P5K-E Wi-Fi (Link)
Q6000 G0 Revision (Link)
Radeon X1950 Pro (Not sure which one yet)
Other components the same

I was going to plump for a HD2900 Pro, but that was REALLY stretching the budget, and the one I wanted has now been discontinued. (boo!)
I'll upgrade to a DX10 card at another point in time.

My question is, If I want to use the P35 chipset to achieve the "free" overclock (1066-1333 FSB) then what RAM am I best off buying - DDR2 1066 or can I get away with DDR2 800?
OCZ 800MHz 4-4-4-15
Crucial Ballistix 1066MHz 5-5-5-15

Obviously budget is an issue. I want to know if I'll get a massive performance drop from the DDR2800, or whether it just won't work at all with a 1333Mhz Processor FSB.

Thanks in advance.
3 answers Last reply
More about build choices
  1. Q6600 has a multiplier of 9 & FSB of 1066:

    Intel FSB is quad pumped. So:

    1066 / 4 = 266.5

    Now DDR2 is double rated. So:

    266.5 * 2 = 533

    To run the Q6600 on P35 at stock, you need only 533Mhz ram.

    Now let's talk about o/cing. Your target is 1333. So:

    1333 / 4 = 333.25 * 9 = 2999.25 or 3Ghz

    The ram to do this is:

    333.25 * 2 = 666.5 or 667mhz

    Any 667/675mhz ram will do this 3ghz o/c. Assuming your pc has a good cpu cooler & case cooling & that x9 is fine for this. Sometimes you lower multi to x8:

    400 * 8 = 3200 or 3.2ghz

    So the fastest ram you should get is 800mhz. Assuming your can achieve 1:1 ratio. Sometimes you do 1:2 ratio. That'll be:

    FSB 400 * 8 = 3200Mhz cpu
    DDR 800 * 2 = 1600Mhz ram
  2. So that's how it works.
    Nice one, thanks very much!
  3. Agreed.. a simply way to sum it up, DDR2 533 memory will run any of the CPU with 1066 FSB at stock.

    The faster memory will give you more room to push it well above what 533 limited to. So if you have a goal, and do the math, DDR2 667 or 800 will normally get you where you want. Any faster memory, you just won't benefit any better.
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