RAM: latency or speed more important?

[Chromana]

Hello, I'm basically trying to upgrade my laptop's memory to the best possible.

My laptop's maximum RAM specs according to the manual:
RAM System Up to 4 GB, 2 x 200-pin DDRII 800 MHz SO-DIMM sockets.

I've found 2 possible sets of memory:

One has a speed of 667MHz and latency 4-4-4-12
http://www.overclockers.co.uk/showprodu ... subcat=936

The other has a speed of 800MHz and latency 5-5-5-15
http://www.overclockers.co.uk/showprodu ... subcat=936

So I am wondering if memory speed or latency is more important for overall performance. If I were to guess I'd say the 800MHz one is better, but I don't know enough about hardware to say. What would you recommend?

[GeorgeH]

Get the 800MHz kit. There's lots of good info out there, but the quick answer is that latency is measured in clock cycles; CL5 X MHz RAM can actually have lower latency than CL2 Y MHz RAM.

Either way, though, you'll be able to tell exactly zero difference between either kit without running synthetic benchmarks - my preference for the 800MHz is simply because that's what your laptop is specced for (but 667 should work just fine if it's significantly cheaper.)

[mosc]

Latency is more important than speed... however the latency is measured in cycles AT that speed. 5 cycles at 800 MHZ is roughly equivalent in wall clock to 4 cycles at 667 MHZ. 667/4 ~ 800/5. You have to keep that in mind when looking at latency figures. You should expect higher latencies as clock rate increases as most of the latency issues involve more than the speed of the memory chip.

[Chromana]

Thanks for your responses guys I went with the 800MHz in the end.