DDR2 Memory Speeds Explained - Page 3 - Overclock.net

prracer6 · 10-06-08

Im new to PC OCing and this is a lot of info, but really good.

Bouncer · 11-10-08

I read this about 4 times finally got it. It's very simple. Nice job.

Slink · 01-02-09

Yes, excellent intro info. Thanks! I used your AMD OC guide to get me started, now I have a 12.5% stable CPU boost.

However, I have a burning question. See, my mobo supports up to DDR2-800 speed. If I buy a higher speed RAM (such as 1066) with the same timings as my current ram (current= 800 5-5-5-15) shouldn't it be easier to achieve tighter timings with the faster ram set to 800 speed? I ask so that I can further my understanding of RAM timings in relation to "speeds". I already know that as speed goes up, timings generally get looser.

Thanks! Please link if you know a good one. There is so much to sift thru here!!

pioneerisloud · 01-02-09

Honestly, AMD CPU's prefer tighter timings vs. Higher speeds. DDR800 @ 4-4-4-12 for example would generally yield higher performance than 1066 @ 5-5-5-15. But honestly you won't see any real world performance difference between the two.

And yes, DDR1066 would likely get tighter timings @ 800MHz. But you can also just get some DDR800 that will run with tighter timings anyway. So its really up to you.

Slink · 01-02-09

Quote:

Originally Posted by pioneerisloud

Honestly, AMD CPU's prefer tighter timings vs. Higher speeds. DDR800 @ 4-4-4-12 for example would generally yield higher performance than 1066 @ 5-5-5-15. But honestly you won't see any real world performance difference between the two.

And yes, DDR1066 would likely get tighter timings @ 800MHz. But you can also just get some DDR800 that will run with tighter timings anyway. So its really up to you.

Thanks! I didn't know about the specifics in regard to AMD chips.

In the light of your answer to my question, I would say that if I can find some higher-speed RAM with extra tight timings, and without an insane voltage requirement, that would be the cream of the crop, right?!

durch · 01-02-09

Quote:

Originally Posted by Slink

Thanks! I didn't know about the specifics in regard to AMD chips.

In the light of your answer to my question, I would say that if I can find some higher-speed RAM with extra tight timings, and without an insane voltage requirement, that would be the cream of the crop, right?!

Ideally yes, but you're going to have a hard time finding memory over DDR2 950 speeds that has anything tighter than 5-5-5-15-2T. Like Pioneerisloud pointed out, buying DDR2 1066 RAM with 5-5-5-15-2T timings and underclocking it to DDR2 800 with 4-4-4-12-2T timings won't be any different than just buying DDR2 800 memory rated for 4-4-4-12-2T timings. 1066 is almost always more expensive than 800 memory, so your best bet is probably to just get a 4-4-4-12 set of DDR2 800.

CPU speed is far more important than RAM speed. Spending a lot of money on a set of RAM isn't a good idea IMO because the difference between running say DDR2 900 4-4-4-12-2T (really good for AMD) or DDR2 900 5-5-5-15-2T isn't really noticeable, but the price difference could be enormous. You'd be better off saving the money or spending it on a better CPU.

As for the statement about low voltage RAM being better, that's not necessarily true. With a CPU, a lower Vid means the CPU will usually overclock better than a CPU with a higher Vid because both CPU's have the same "max voltage" that can be safely applied, so the CPU with the lower Vid has more headroom. The same is NOT true with RAM, and the reason for this is different RAM uses different ICs (internal controllers). The IC of the memory determines the voltage needed and the overclocking capability of the module. A lot of the memory with lower voltage needs use ICs that frankly do not scale well with voltage. So even though one memory stick with a certain IC can run 2.2v no problem does not mean that a different memory stick with a different IC rated for say 1.9v can safely run 2.2v, or that increasing the voltage to 2.2v will give any improvement in stability.

Slink · 01-08-09

Okay, I don't wanna come off as weird, but I pretty much love you. Hahaha. (You have been incredibly helpful in multiple instances, and I am thankful.)

Thank you so much for the heads-up. I have to say, I could keep cranking my CPU a bit, but the RAM gives out, unless I loosen the timings. I had everything running pretty hot for a few min to test limits, and with RAM running at tighter timings, I saw a pretty intense boost in speed (but the system was STILL unstable).

Whatever the case, my CPU is still weak, and I plan on upgrading. The RAM that I have is definitely a bottleneck, but as CPU speed goes up, RAM does so proportionately (until you need to loosen timings) right? -Thanks!

Quantum Reality · 01-11-09

Thanks for the tutorial and info. This answered some odd CPU-Z data I saw.

(see attachment)

However I am wondering why memtest86+ thinks my DDR2-667 @ 600 is 685? Is memtest not reading the divider/memory speed/whatever-it-is properly? If it helps I have am Asus M3A whose BIOS has "Limit" and "Manual" settings. I have it at Limit DDR2-800 presently, but the board is obviously still choosing to go by the SPD. It is Kingston 4-4-4-12 DDR2-667 and I've heard reports it can be safely taken up to 800. So I guess I could just solve my problem completely by fixing it at 800 and calling it a day.

But some analysis of this anomaly would be helpful.

durch · 01-11-09

Hmm, what CPU are you running with the DDR2 667 memory? I'm not sure if Phenoms follow these same rules, but there is absolutely no way to set the speed of the memory independently of the CPU speed for X2's. They MUST follow the rules in this guide. I'd trust CPU-Z over Memtest, but you should be able to verify the speed on your own doing the math.