DDR2 Speeds

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Standard name Memory clock Cycle time I/O Bus clock Data transfers per second Module name Peak transfer rate
DDR2-400 100 MHz 10 ns 200 MHz 400 Million PC2-3200 3200 MB/s
DDR2-533 133 MHz 7.5 ns 266 MHz 533 Million PC2-4200
PC2-43001		 4266 MB/s
DDR2-667 166 MHz 6 ns 333 MHz 667 Million PC2-5300
PC2-54001		 5333 MB/s
DDR2-800 200 MHz 5 ns 400 MHz 800 Million PC2-6400 6400 MB/s
DDR2-1066 266 MHz 3.75 ns 533 MHz 1066 Million PC2-8500 8533 MB/s
Source: Wikipedia

At this point, mainstream users should go for branded DDR2-800 memory. Quicker timings (low CL values) are favorable, but you shouldn’t fork out considerably more money, as the differences are small. DDR2-1066 is important for systems based on AMD Phenom processors, as their memory controllers can utilize the faster memory.

DDR3 Speeds

Standard name Memory clock Cycle time I/O Bus clock Data transfers per second Module name Peak transfer rate
DDR3-800 100 MHz 10 ns 400 MHz 800 Million PC3-6400 6400 MB/s
DDR3-1066 133 MHz 7.5 ns 533 MHz 1066 Million PC3-8500 8533 MB/s
DDR3-1333 166 MHz 6 ns 667 MHz 1333 Million PC3-10600 10667 MB/s[4]
DDR3-1600 200 MHz 5 ns 800 MHz 1600 Million PC3-12800 12800 MB/s
Source: Wikipedia

At this point we recommend waiting on purchasing DDR3 memory, as most speed grades are still considerably more expensive than DDR2 RAM, without delivering better performance. Even when it comes to high capacity memory kits, you can get much cheaper deals on quad 2 GB DDR2 DIMM packages than on comparable DDR3 memory.


Talkback
Fidens1 10/04/2008 10:28
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Fidens1
"It’s worth noting that DDR2 memory is amazingly affordable at its current pricing point. 4 GB kits look especially appealing, but remember that you’ll need a 64-bit operating system to take advantage of all of it."

That's not strictly true. Windows Vista SP1 can now recognise 4GB of RAM on a 32 bit system.

ducker19 10/04/2008 10:29
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ducker19
As always, a very interesting article. I had heard that Vista 32 bit SP1 was going to have 4Gb memory support. Is this correct?
Fidens1 10/04/2008 10:37
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Fidens1
And before you say "Vista SP1 only recognises the RAM but does not address it." you could use Physical Address Extensions to utilise the extra RAM.
Jimmy O 10/04/2008 01:02
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Jimmy O
What I found interesting is that on the C2D, the 667 MHz 3-3-3-8 pretty consistently outperformed the 800 MHz 3-3-3-8. Apperantly, the 1:1 divider is so much more efficient than the 5:6 divider, that the clock speed is a smaller factor.
I have a C2D 8400 running with DDR2-800, I'm gonna try if running it at 667 MHz will improve performance. Didn't expect that.
Matt26LFC 10/04/2008 01:07
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Matt26LFC
32bit OS's cant use 4Gb of RAM its a limitation of the x86 architecture. 32Bit OS can only address up2 4Gb if u have a GFX card with 512Mb theres half a gig gone there and then so windows could only use the remaining 3.5Gb for RAM. Now jus imgaine 2x 8800GTX's in Sli 768Mb Each!!
Fidens1 10/04/2008 02:46
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Fidens1
Does anyone read previous posts?
and...
I'm sure graphics cards with any amount of RAM use it independant to whatever Windows has so I'm pretty sure what Matt26LFC said is not quite correct.
Taniniver 10/04/2008 02:56
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Taniniver
Fidens1 - there is no difference between Vista and Vista SP1 in their ability to address 4 Gb of RAM.

The only difference is that under SP1, Vista displays the amount of INSTALLED RAM rather than the amount available to Windows - see the information in the Microsoft article about the Vista SP1 changes, here:

http://technet2.microsoft.com/Wind [...] x?mfr=true

It's the second bullet point under the "General Improvements and Enhancements" section.

As for Physical Address Extension, that's something quite different, and not unique to Vista SP1 or even to Vista - Windows XP can do that.
MinskUK 10/04/2008 03:08
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MinskUK
Matt26LFC is correct. Although the RAM on the graphics card is independant, it still forms part of the total addressable space. Running a 64bit OS resolves the addressable memory barrier even if it does introduce other side issues...
Fidens1 10/04/2008 03:37
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Fidens1
Yes, but with SP1 you can now "SEE" the amount of RAM installed (up to 4GB) as well as use it with Physical Address Extensions. So really, going back to the article, you can use 4GB and see it in a 32 bit system.

Using Physical Address Extension, surely this could offset the RAM on the graphics card?
MinskUK 10/04/2008 07:24
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MinskUK
Even with PAE, addressable space remains at 4GB in a 32 bit OS. PAE provides a mechanism where by memory beyond 4GB can be used by applications capable of making use of it, for example, SQL server. It does this by creating multiple processes.
leexgx 11/04/2008 03:09
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leexgx
PAE is patchy at best when used not thing you norm use (and vista does not support it officialy and will more then likey result in an BSOD alot)

Vista 32 and vista 32 SP1 Does Not support more ram then each other, Vista NOW reports the Amount Of Installed RAM Not what is usable what very poor way that microsoft have done this as now thay are hideing the fact that laptops with 256mb shared ram does not show it been used any more, thay should of shown both ways total installed total usable (and an help box to explane why usable is lower then installed)

Plase task manager (press Ctrl-Shit-Esc will open it as well) and click on performace and you see how much ram is usable there under Physical > total {4gb = 4000 ish}

with an 32bit OS with 4gb depeding on more then 1 video card is in use or motherbaord as well it be anywhere between 3.5gb {3500 ish} all the way down to 2gb {2000 ish} of useable ram on Any 32bit os
Matt26LFC 11/04/2008 11:26
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Matt26LFC
Cant believe the way microsoft have handled this, trying to make people think they can now use 4Gb+ i agree with u leexgx that should show both values and throw in a help box to explain.
GavinT 11/04/2008 01:04
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GavinT
Any chance of you doing the same or similar tests on an AMD Phenom system?
bnot 15/04/2008 06:29
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bnot
Power consumption?
petar 16/04/2008 01:29
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petar
Is Aeneon's semi transparent (x layers PCB) with aeneon chips much slower than decent looking Buffalo sticks and both of them much slower than OCZ sticks. All ddr2 800, 5-5-5-12?

Anyone compared this low cost sticks with high cost sticks? Any differences in %?
tea drinker 22/04/2008 11:25
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tea drinker
So if you already have 2 gig installed, have 1 gig of graphics RAM, what size swop file can you use? Is it addressed differently?
joe11112222002 23/04/2008 11:23
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joe11112222002
I Have an Asus P5N T Delux Motherboard with an intel Qx9650 CPU a 750GB Seagate Barracuda with 32Mb Cache and also have 2xGeForce 880GTX Graphics cards with 768MB DDR3 memory and 8GB of PC6400 800 Geil Black Dragon Ram can anyone tell me if its possible to run faster memory with my setup or would it not be cost effective to go for faster memory? I have Vista Ultimate 64Bit OS which recognises my 8GB of Memory and I have 6280MB Free. What memory would be best for this setup and where can I get it from? my systems Motherboard has a 1333FSB I think sorry to be so vague but I dont know a lot about memory or motherboards.

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