: DDR2-667 or DDR2-800?


kloan
Mar 4th, 2008, 04:20 PM
Would there be a noticeable difference in performance between the two, using in a Macbook with the 800mhz FSB?

CanadaRAM
Mar 4th, 2008, 04:24 PM
??? In what machine?

There would be absolutely no difference in performance on any Intel Core2Duo Mac. The macs are hardwired at 667, and there are reports of the new Penryns crashing and burning on 800 mhz SODIMMs.

Stick with the 667s for Core2Duos.

The 2008 MacPros, of course, must use 800 MHz FB-DIMMs, no others.
the 2007 MacPros will not benefit from 800 Mhz, stick to 667 FB-DIMMs with them/

kloan
Mar 4th, 2008, 04:33 PM
Just realized I forgot to post what machine, edited but you already replied (didn't refresh page)..

Anyway, given the the Macbook I'm looking at (2.2Ghz, 800mhz FSB) can take 800, would it be noticeable in performance? The price seems about the same for 2x 2GB.

Also, since the graphics shares memory, would 800 still be compatible with it?

CanadaRAM
Mar 4th, 2008, 06:02 PM
There is zero, zilch, nil, performance benefit to 800 MHz RAM in a machine that runs a 667 MHz memory bus.

Your machine has an 800 MHz Frontside bus. And a 667 MHz memory bus, not an 800 MHz memory bus. Memory and FSB are not the same thing.

kloan
Mar 4th, 2008, 07:46 PM
It just says 'System Bus' on the Apple website... is that memory bus or FSB?

I was under the impression that FSB is the speed the CPU can communicate with the ram... so then that would mean they are the same, no? Afaik, the newer Macbooks run at 800mhz 'system bus', which I believe is the same as FSB or memory bus... but please correct me if I'm wrong (with an explanation of course ;))

Well, either way from benchmarks I've seen on a few review websites, it doesn't look like there's really that much benefit to 800mhz ram, even if the system does support it... and the 667 is still a few bucks cheaper, so I guess that's what I'll go with...

EDIT: Ok, after reading up on it on the Wiki... do new Macs even have frontside bus and memory bus? Or has it just been replaced with 'system bus'?

CanadaRAM
Mar 4th, 2008, 08:13 PM
Yes, Macs have a Frontside bus and a memory bus.
No, the two do not have to be linked. Memory often runs at a different multiple than the FSB -- PC overclockers can experiment with different multiples on some desktop motherboards. In the Intel Macs the memory bus is locked down at 667 MHz.

System Bus refers to the Frontside bus, the primary highway out of the CPU. When Apple advertises a 800 MHz system bus, it doesn't necessarily follow that all the other busses on the machine are the same MHz.

kloan
Mar 4th, 2008, 08:36 PM
ah, okey doke.. thanks! 667 it is. :)

Lee_Roy
Mar 4th, 2008, 09:39 PM
Do they even make DDR II SO-DIMMS in 800mHz, I thought they only made them in 667mHz. The online retailers I checked don't list any 800mHz SO-DIMMS.


Oops, I checked another retailer and yes they do make them, but not many to choose from. I wonder why Apple isn't putting these in the new MacBook Pros at least.