YAD(DR2)T

[zeruty]

Hey,

I used to know everything I needed about memory & fsb speed, back in the DDR & Athlon XP days... back when picking the optimal memory speed was as easy as my ex.

But I've been out of the game lately...

I've been looking at swapping memory around in some of my employer's computers, and need to confirm some details. We are removing some computers that are EOL, and I want to save the memory to upgrade other computers. (Obviously, overclocking is not a concern at all)

I've researched and found some of the information I need. However, a lot of the stuff I've read was dated in 2006, 2007... So it's hard to discern if any of it is now inaccurate.

So... DDR2 is Double Data Rate (Duh) while the newer Intel CPUs are Quad Data Rate.

So my understanding... is that, for example...
An 800Mhz FSB cpu really is:
200Mhz x 4 = 800mhz FSB
200Mhz x 2 = 400mhz memory.

So theoretically, DDR2-400/PC2-3200 would be the matched speed for the 800Mhz FSB cpu, running at half the speed. Correct?

I've heard it stated that increasing the memory speed doesn't make much difference until you get to the synchronous state, so that would be DDR2-800/PC2-6400. But I've heard that it's worthwhile to bump up one rating, in this case DDR2-533/PC2-4200.

What is the truth to both of those statements? Is there a worthwhile benefit from running memory faster than the 2:1 ratio?

I've also read that Core 2 Duo's get a worthwhile gain from running the memory 1:1. Is that true?


I'll post a reply to this shortly with some specific details....

 

[zeruty]

So here is what I'm working with.
The main point of the upgrades is to increase memory, and adding an additional stick to systems with only 1, so the memory can run dual channel.

I just want to use the available memory the most optimal way I can, giving some computers performance boosts due to higher memory speed if possible.

We'll have spare DDR2-533/PC2-4200 & DDR2-667/PC2-5300

Dell GX280's with Celeron D 335 533Mhz FSB
Currently have DDR2-400, any point upgrading to DDR2-533?

Dell GX620 with Pentium 4 640 800Mhz FSB
Currently most systems have DDR2-400 and DDR2-533 mixed. Any point swapping out 400's and replacing with 533, so the system runs the memory at 533?

HP DC7700 with Celeron D 360 533Mhz FSB
Currently they contain DDR2-667. Do these get any benefit from the faster 667Mhz memory, or should I consider swapping in DDR2-533 so the 667 can be put to better use elsewhere?

HP DC7700 with Pentium D 945 800Mhz FSB
Currently they have DDR2-800. Do they benefit from the 1:1 ratio or should I consider swapping in DDR2-667 or DDR2-533 to put the DDR2-800 to better use elsewhere?

 

[Ben90]

You are correct with the DDR->FSB conversions
Looks good enough to me, from what ive seen as long as its over a 1:1 ratio, the ram speed doesnt really matter too much, the difference between a 2:1 ram:fsb and a 1:1 might be like 1% real world performance

 

[Emulex]

some boards and memory may be able to run tighter timing at lower FSB.

 

[zeruty]

Originally posted by: Ben90
You are correct with the DDR->FSB conversions
Looks good enough to me, from what ive seen as long as its over a 1:1 ratio, the ram speed doesnt really matter too much, the difference between a 2:1 ram:fsb and a 1:1 might be like 1% real world performance

Thanks...

Sorry, I'm confused about one thing...

I guess I'm not certain on the x:y ratios...

When you say 2:1 ram:fsb are you referring to for example ddr2-800(400mhz) memory with an 800mhz(200mhz) fsb? Or would 800 with 800 be considered 1:1?