a short answer - its all to do with the memory speeds. If your CPU is running at 300FSB, having a 1:1 ratio will mean that your memory would need to run at 1200Mhz. In the majority of situations you will find that anything higher than 4:5 wont give you any real benefit.
a short answer - its all to do with the memory speeds. If your CPU is running at 300FSB, having a 1:1 ratio will mean that your memory would need to run at 1200Mhz.
You sure on that Vincent? With a 300FSB the CPU will run at a rated quad-pumped FSB of 1200Mhz, and a DDR2 RAM with a 1:1 ratio will run at 600Mhz?(DDR for Double Data Rate)
As you can see, I'm currently running a FSB of 470 on my PC, with a 1:1 ratio my memory is at 470*2=940Mhz
Its correct... DDR2 is double rate of the FSB Bus. Normally the memory would come at 1:3 but if you overclock by increasing massively the fsb to get more out of CPU and Graphics you run the risk of getting an unstable overclock as the memory would be running at silly speeds. As they wouldn't cope the PC would throw a wobbly. You could throw more voltage and cooling at the memory and in some cases you might get away with it but if you go for FSBs at your speeds the most likely is that they wouldn't cope (490X3=1470Mhz!! ... 2940MHz effectively for DDR2...) the new 1333MHz FSB Processors run on 4X333MHz which would take your memory to 999MHz (X2 effective) hence the dominators and other work comfortably at over 800Mhz as the bus handles their speeds and they have some headroom for oc.
I hope I explained myself properly as I sometimes try to give too much information and also because I'm not too confortable with this as I am also learning.
Its correct... DDR2 is double rate of the FSB Bus. Normally the memory would come at 1:3 but if you overclock by increasing massively the fsb to get more out of CPU and Graphics you run the risk of getting an unstable overclock as the memory would be running at silly speeds. As they wouldn't cope the PC would throw a wobbly. You could throw more voltage and cooling at the memory and in some cases you might get away with it
Or you can just lower the multiplier in BIOS to 1:1, which with a FSB of 490 will give 980Mhz rated FSB, which is 20Mhz under the PC2-8000 specification, or a DDR2-1000.
Eu wrote:
the new 1333MHz FSB Processors run on 4X333MHz which would take your memory to 999MHz (X2 effective)
The 1000Mhz from the new spec is derived from a 2:3 Multiplier. To be able to get ~1000Mhz from a FSB of 333, divide 1000(Rated frequency) by 2(DDR), which is 500Mhz. System(333FSB/2)=(500FSB/3)Memory.
To have a DDR2 memory running at almost 2Ghz effective is currently not possible, as the fastest Corsair memory runs at 1250Mhz *effective*, or PC2-10000.
Also is there a 1:3 multiplier for DDR2? that sounds awfully high.. with a FSB of 266 on a 1:3 multi, the rated FSB will be at 266*3=798FSB, 798*2(DDR)=1596Mhz Rated, well over the fastest specifications of current DDR2s
Well I've overclocked an e2160 to 3GHz (that's 333 x 9) so my ram is only running at 666MHz when its actual native is 800Mhz. That means I gotta get my CPU to 3.6GHz... haha never going to happen.
Weirdly enough I always used to run my memory at 1:1 - so with 1600 I was running 800mhz - but I've also found that running 1:1.2 seems to work will with stability on the 680i, so I'm now running 960mhz.
Oh I've done some overclocking from the 3GHz... my E2160 runs at 3.42GHz now, ram running at 790 Mhz. Would I be able to overclock further when dropping the multiplier?
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