understanding RAM speeds

[Matt Sugden]

hi I'm looking at two different machine specs today and trying to decide which to go for. One system is AMD based and the other is Intel.

 

I'm a little confused with modern Ram terminology.

 

In terms of the 9500 AMD spec, the mobo supports 800mhz PC6400 Ram, and the overall cost is £40 per PC cheaper, I'm hoping to be buying two.

 

The Intel Q6600 spec has a mobo supporting for 667mhz PC5300 Ram.

 

I believe the Quad Q6600 chip is supposed to be slightly better than the AMD, however wouldn't the difference in Ram clock speed have a big influence on the overall system performance?

 

To Spec the Intel with a 800mhz ram and mobo the price will go to high, before the obvious is stated.

[shaneis]

Assumiong you don't intend on overclocking the system, the easiest rule of thumb I've seen for RAM is to first find your CPU FSB (for 1066MHz for the Q6600). You then aim to match your RAM to 1:1, so if you had dual channel RAM @ 533MHz (read 2 x 533 = 1066) you achieve a 1:1 setup. Ideally, your motherboard will have the same BUS speed. You can use a 1066 FSB CPU (Q6600) with a motherboard/ RAM combo at 1333MHz (dual-channel 667MHz), but the extra is effectively wasted as the CPU is limited to 1066. It may even benchmark a little slower too...provided you have good quality (low latency) RAM.

 

The next factor is price/ availability/ scalability. As dual-channel 533MHz is getting harder to find/ more expensive, it's better to buy 667MHz RAM (more availability and relatively cheap) if you can't find some good quality 533MHz RAM. 800MHz RAM would only be a viable option for a Q6600 setup if you intended on overclocking as it will take higher clock speeds whereas the 667MHz RAM will only clock so far, or if you have a motherboard at 1600MHz and intend on upgrading to a 1600MHz FSB CPU in the future, like the (absurdly-priced-yet-strangely-desirable) QX9775.

[Matt Sugden]

Thanks for the info.

 

Makes sense to me.

[Chris Potts]

Me too. Thank for information.

 

Cheer.

[AJLynn]

You actually don't have any choice in the matter - the RAM speed is determined by the CPU's spec. The RAM used must be rated to run at at least the speed the CPU wants it to run at. If you use 800MHz RAM with a CPU that is rated to use 533MHz RAM, the RAM runs at 533MHz. If you're building a system for overclocking, you buy the 800MHz RAM anyway, because when you overclock you will be running it faster than the original 533.

 

The fact that the Q6600 is intended for 533MHz RAM is a good thing for overclockers, because the 800MHz RAM is cheap and it gives you a lot of head room.

 

Now, since the RAM speed is locked in to the CPU, when buying a PC that is not meant for overclocking, you can ignore the RAM speed entirely - just forget about it completely, because it has no bearing on your decision. Look at the CPUs available and look at testing on sites like tomshardware.com and anandtech.com to compare the CPUs' performance in Cinebench and Max tests without overclocking. You will find that even though the AMD is using faster RAM, the Intel is faster - in fact, in the benchmarks I saw after AMD released this line of chips, all of the Intel quads beat all of the AMD quads in all of the rendering and video encoding tests.