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Old 11-16-2005, 12:09 PM   #1 (permalink)
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Default memory overclocking

When overclocking memory, I hear a lot about needing the memory clock speed to be the same as the FSB of your CPU. Does this refer to the system clock speed of the CPU (core speed of the processor without quad/double pumping technology) or the FSB speed?

ie: I have 2 sticks of DDR400 (PC3200) RAM installed with an Intel pentium 4 800MHz FSB rating (System clock 200MHz)

The clock speed of DDR400 I believe is 200MHz. (as I read in the overclocking guide on this forum) So correct me if I'm wrong, the clock speed of DDR 400 (200MHz), should be the same as the system clock of my 800MHz FSB processor (200MHz)? As long as those two clock speeds match up (overclocking as well), then I'm not losing any performance?

Basically what I'm asking is in overclocking, it's refering to the actual clock speeds and not the quad pumped FSB speed, correct?

Oh and one more question, In dual channel mode, in my case, my memory would run at 400MHz and not 200MHz. This would be double the clock speed of the CPU's system clock. Since the system clock is 200MHz, and the dual channel would be running at 400MHz, would this add a decrease in my memory performance and only allow it to run at 200MHz?
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Old 11-16-2005, 12:43 PM   #2 (permalink)
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Memory speed is linked to the FSB, so increasing the FSB will increase the speed of the memory.

For Intel systems, it is still rather important to keep the ratio of RAM and FSB at 1:1. Meaning if FSB is 200, RAM is 200. This should be the stock setting on your system.

So yes, the clock speed of DDR400 is 200MHz, and the FSB speed the guide refers to is 200Mhz, not the "quad pumped" speed of 800.

Dual channel does not double the clock speed of the RAM, so this has no effect on what you are asking about. RAM running in dual channel just means the system can access both sticks at the same time, theoretically "doubling" bandwidth, but the actual clock speed remains the same.
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Old 11-16-2005, 12:47 PM   #3 (permalink)
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Default Re: memory overclocking

Quote:
Originally posted by X2Xtreme360
When overclocking memory, I hear a lot about needing the memory clock speed to be the same as the FSB of your CPU. Does this refer to the system clock speed of the CPU (core speed of the processor without quad/double pumping technology) or the FSB speed?

ie: I have 2 sticks of DDR400 (PC3200) RAM installed with an Intel pentium 4 800MHz FSB rating (System clock 200MHz)
Yes, if you have an Intel system, then the memory speed needs to be the same as the system FSB. Setting a memory divider causes Intel systems to lose performance since the CPU talks to the memory throug the Northbridge. When you raise the FSB speed, it automatically raises the memory speed, thus requiring memory that can sustain high clock speeds (overclocking memory).

Quote:
Originally posted by X2Xtreme360
The clock speed of DDR400 I believe is 200MHz. (as I read in the overclocking guide on this forum) So correct me if I'm wrong, the clock speed of DDR 400 (200MHz), should be the same as the system clock of my 800MHz FSB processor (200MHz)? As long as those two clock speeds match up (overclocking as well), then I'm not losing any performance?
Yes

Quote:
Originally posted by X2Xtreme360
Basically what I'm asking is in overclocking, it's refering to the actual clock speeds and not the quad pumped FSB speed, correct?
Yes

Quote:
Originally posted by X2Xtreme360
Oh and one more question, In dual channel mode, in my case, my memory would run at 400MHz and not 200MHz. This would be double the clock speed of the CPU's system clock. Since the system clock is 200MHz, and the dual channel would be running at 400MHz, would this add a decrease in my memory performance and only allow it to run at 200MHz?
OK, no. Where do people get this **** about Dual Channel doubling the clock speed. It DOESN'T. It just gives each stick of RAM its own bandwidth so 2 sticks aeren't fighting for 3.2GB/s of bandwidth. It raises performace, but doesn't double the bandwidth, nor the clock speed.
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Old 11-16-2005, 12:56 PM   #4 (permalink)
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OK so is this information wrong?

http://www.tigerdirect.com/applicati...829&CatId=1304

Go down to memory speed in the specs part, it says 400MHz PC 3200

I thought it was DDR400 (200MHz), not 400MHz
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Old 11-16-2005, 01:01 PM   #5 (permalink)
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Its both wrong and right. The CORE Clock speed, the one thats actually there is 200Mhz. But the EFFECTIVE clock speed, the one that runs the processes is 400MHz.

If you count the clock cycles, its 200MHz. But "double-pumping" allows it to perform like 400MHz. They are able to send an instruction on the rising edge of the clock cycle, and another instruction on the falling edge of the clock cycle. One clock cycle = 2 instructions. Thus EFFECTIVE 400Mhz (which is supposed to be called DDR400, not 400MHz), but Core 200MHz.

All that has NOTHING to do with Dual Channel.
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