CPU vs RAM

[kch1]

With my system at default i run my DDR @ 400MHZ however if i try and overclock the CPU (fsb even as little as 7MHX extra) i have to throttle the RAM back the 333MHZ. Whats the best compromise - a) default clock and 400MHZ memory or b) overclock with slower memory?

Thanks

P4 2.8
Abit SR7-8X
1GB PC3200 (2x512MB)
Gf4 Ti4600
etc.

 

[Tinker]

Hello kch1...

I would think that would depend on how much the programs that you run are dependent on the memory. If large amounts of transfers occur from the memory to the CPU then the speed is going to suffer to the memory speed. If this is the case then slowing down the memory will slow down the whole system no matter what the CPU speed is set at.

Another thing to look at is that when you up the bus speed for the CPU you also up it for the memory. In affect you may turn down the memory to 333 but you are also OCing the memory at the same time, meaning the memory is running faster than 333..

 

[Eck]

Hmm. I didn't think that was the case. If I increase the FSB, the memory speed remains the same in CMOS, and I thought it would stay the same. But if what you're saying is true, I would see a big performance gain if I increased the FSB and decreased the clock multiplier?

 

[Tinker]

My understanding of the system bus clock is that it runs the FSB for the CPU and it is also the clock for the memory. For example, I have a Intel D850EMV2L mother board that auto detects the CPU speed. I have a P4 2.4 @ 400FSB. Now the MB will run at 400 or 533. The problem is that I have to have the 40 ns RAMBUS to run at 533. As much as I hate to say it my RAMBUS is only 45 ns and hence to slow to run the 133 Mhz bus speed for the 533 CPU. My FSB is 400 or 4x100 the bus clock speed. So by changing the FSB you have to up the bus clock over and above the 100 Mhz. Indeed by changing the multi player for the CPU you should then only effect the CPU speed and can leave the FSB at 400. If the memory used is not fast enough to handle the increase in bus clock speed (100 Mhz) then problems will occur......

 

[Mr Dead]

I know that for my mobo, an abit kx7-333 Raid. The memory runs at 166fsb and the processor at 133 fsb. You can up the processor fsb and it will only effect the memory speed when you go over the 166 fsb mark..

 

[Taurus]

Originally posted by Mr Dead
I know that for my mobo, an abit kx7-333 Raid. The memory runs at 166fsb and the processor at 133 fsb. You can up the processor fsb and it will only effect the memory speed when you go over the 166 fsb mark..

so, if you overclock your fsb to, say, 145mhz, your memory will still run at 166mhz? positive?

 

[Mr Dead]

Positive thats the way it works on my mobo anyway!!!

 

[kch1]

I wish I could get my mobo to fix the dram frequency, i have the various dividers but all i can fix is the agp to pci ratio. I use an Abit SR7-8X, what was the mobo that can fix the ram frequency again?