[jblaze]

I'm trying to max out my ram on my Dual 1Ghz QS and I had heard to load up on CL2-rated RAM. If the current RAM is CL3, should I stay with CL3 or would mixing CL2 and CL3 be ok for the machine? I do a lot of video editing, would CL2 RAM give me any noticable system improvement?

[Eriamjh]

CL2 or CL3 won't matter.
No, go ahead and mix 'em.

The system will run at CL3 speeds when mixed.

Even if you went all CL2, I doubt you would see any difference except in long renders (2 hours reduced to 1h55m).

[Detrius]

http://www.barefeats.com/memory.html

This was with a G5, not a G4, but it still holds true. There is no real-world difference.

As the benchmarks show, it doesn't make a difference.

My explanation:

The CL3 vs. CL2 rating means 3,2,2 vs. 2,2,2. What that means, is that the first byte accessed will take three clock cycles to get back to the processor instead of two, while each successive memory access only takes two clock cycles. Therefore, the difference is a single processor clock cycle lost when accessing just a single byte of memory. This is irrelevant. If a program is accessing a single byte of memory many times, it had better be in the registers if not the L1 cache. Worst case scenario, that single byte of memory is in the L2 cache. If it isn't in the L2 cache, it hasn't been used in a long time, and no program has enough individual variables to fill the L2 cache.

I would think that it may turn that two hour render into a 1 hour, 59 minute, 59 second render... Closing down your email program or turning off the screen saver will make a bigger difference than that.

[Detrius]

as an aside... 2,2,2 memory should be 33% faster than 3,3,3 memory, and that assumes that the fourth, fifth, and sixth (and so on) memory accesses follow the same pattern.