RAM Timing Question

[d0lorous dave]

I was just given two 512MB DDR2 667 chips for the new computer I'm building (which supports up to 800mhz RAM) and the timing says 5-5-5-12, I assume that's bad, right?

If it is bad, how bad is it? Will I notice a drop in performance in gaming compared to RAM with lower timings?

 

[Boyo]

It all depends. What RAM are you currently using and what are the timings? If they are worse, then throw in the two sticks that you received for free. The timings aren't the greatest, but they aren't that bad either.

 

[Roguestar]

Well for free they're certainly not to be sneezed at! What RAM are you currently using? Is your CPU overclocked at all?

5-5-5-12 is not neccessarily bad. I'm running my RAM sticks at 5-5-5-12 because they're overclocked from 533Mhz to 920Mhz.

 

[d0lorous dave]

I haven't actually put the PC together yet, so they're not replacing anything. My current PC is still running DDR333.

 

[Ruptga]

Those timings are fine, they're not going to epenis++, but at the worst you will lose 3fps because you're not running at 4-4-4-12. that goes for AM2 platforms as well as Core 2 Duo, Anandtech has consistently shown that they're not sensitive to memory bandwidth or latency changes.

http://www.anandtech.com/memory/showdoc.aspx?i=2900&p=8
(sixth paragraph from the top, starts of as "The question that remains is")

 

[d0lorous dave]

Outstanding replies--thanks so much.

I'm hoping obviously to be able to afford a 2GB DDR2 800 kit at some point in the near future but I'm thinking the DDR2 667 will be just fine with minimal performance loss on the lower clock speed.

And if the timings don't make a huge difference, I'm not worried about it.

 

[Ruptga]

Oh I about forgot, if you have an AM2 platform, run the memory at 667, but if you have C2D, run it at 533. Intel still has the pitfall of the FSB; increasing memory speed always helps, but running your memory at the same speed as your FSB helps more. In more precise language, 533 is good, 667 is not so good, but then 800 is better than 533. There's a technical explaination, but the simple answer is that it's just not good for the two busses to be out of sync.

If you're not bothered by the loss of warranty, you can easily overclock your C2D so that your memory will run at 667 and be in sync with the FSB. C2Ds often and easily do this with the stock Intel CPU cooler and at stock voltage, so it's just a matter of going into the bios and upping the FSB from 266 to 333mhz.

 

[d0lorous dave]

I bought an AMD X2 4600, does that make a difference?

 

[Roguestar]

Originally posted by: ADDAvenger
Oh I about forgot, if you have an AM2 platform, run the memory at 667, but if you have C2D, run it at 533. Intel still has the pitfall of the FSB; increasing memory speed always helps, but running your memory at the same speed as your FSB helps more. In more precise language, 533 is good, 667 is not so good, but then 800 is better than 533. There's a technical explaination, but the simple answer is that it's just not good for the two busses to be out of sync.

Technical explanation please. I'd like a citation.

Empirical data collected in the CPU/OC forum shows that a 4:5 memory ratio delivers slightly increased performance over 1:1. Go read the 1:1 vs 4:5 memory thread there.

 

[Ruptga]

Technical reason: I frankly have no idea what the right name is, but one of the specific latencies (tRas or something, I don't know) effectively doesn't exist because the memory and the FSB is resting at the exact same time, but when they're out of sync you have twice of that specific kind of latency.

Anyway, it's entirely possible that I'm wrong, I'm not a memory expert, but the above is what I had been told on the forums and read in reviews.

 

[Ruptga]

Originally posted by: d0lorous dave
I bought an AMD X2 4600, does that make a difference?

The memory divider/FSB thing is moot for you since you have AMD, just put the memory in and you're good to go, it'll set itself to 667 which is what you want.