RAM - What to look for?

[amanat69]

When buying RAM, what should I look for? I'm confused to how it all works. Like the latancies, what does 5-5-5-15 mean etc? Can someone explain it please?

 

[Kuberr]

Assuming you're talking about DDR2, first off, the RAM speed, as in DDR800, DDR1000, etc.

The higher the better, and usually, the more expensive it is.

Timings indicate the length of the delay when the memory performs different tasks, such as reading and writing. The smaller these timings are, the better.

The 5-5-5-15 that you are talking about is:
tCAS-tRCD-tRP-tRAS

The most important is the first one, the CAS timing. The others are not as significant to performance (but they do add bragging rights).

If you go from DDR533 and up, you will notice that while the RAM speeds go up, so do the latencies. The performance you gain from the speed outweighs the cons of the higher timings.

 

[amanat69]

Thanks Kuberr! You've answered loads of my q's. Thanks . Do you have msn?

 

[ownage]

For DDR2, CAS latency isnt the most important thing. It plays a decent sized role, but others do too. Some RAM will run 3-3-3-1, while others can only run 3-4-4-8. You can see a speed increase with 3-3-3-1 in benchmarks even though the CAS is the same.

Latency is basically how many cycles it takes. So think of CAS, CAS to RAS and all the others as a train station. And the numbers it takes is like the number of mintues it stops at the station. You want to finish the route as fast as you can.

 

[amanat69]

oo right, so all the numbers are equally as important? so in a sense, 25% each?

 

[ownage]

you could say it that way. But its not proportional.

 

[Kuberr]

Yeah, if you look on the side, you can see my AIM and MSN.

Performance isn't impacted that greatly by latencies. The lower the better, but the different they make is not worth crying over, at least it wasn't for DDR.

 

[amanat69]

O right thanks . SO i'm sure the latencies dont matter with ddr2 then? So what are the proportions?

 

[Kuberr]

They matter, but it's not even close to 25%. For DDR, it was about 3% from 2-2-2-5 to 3-3-3-8. I'm not sure about DDR2 though, but I doubt it's much more than that.

 

[amanat69]

I'm so confused :S. So the latency isnt a big issue, it's more about the speed? Btw, i added you to msn. What I mean was.. for example 2-3-4-5 then the 2 = 25% so does the 3 and so does the 4 and so does the 5. So they are all equally important to look at? Or should i just shut up lol