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DDR2 and DDR3 Memory Round Up

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The new Intel P35 chipset is an intriguing piece of silicon as it supports both DDR2 and DDR3 system memory. The slots for these two types of memory are mechanically and electrically different to each other so most P35 motherboards support either DDR2 or DDR3. The Gigabyte GA-P35C-DS3R does things differently as it supports four DDR2 slots and two DDR3 slots so you can use DDR2 today with the prospect of an upgrade to DDR3 tomorrow.



This is good news as it gives us a platform that can be used to make a direct comparison between DDR2 and DDR3, allowing us to get answers to two questions that have been burning us for some time. First, we know that fast memory is better than slow memory, but is there a point where you hit a ceiling where increased memory speed doesn't offer an advantage? Second, and rather broader, is DDR3 a worthwhile upgrade from DDR2?

As mentioned, we used the Gigabyte GA-P35C-DS3R in conjunction with a Core 2 Duo E6750 that runs at 2.66GHz on a 1,333MHz FSB along with a Western Digital 150 Raptor hard drive. The graphics card isn't especially important for memory testing so we plumped for a Sapphire X1950 GT, just to ensure it wasn't any sort of bottleneck in system performance.

The operating system was Windows XP SP2, rather than Vista, as we didn't want the quantity of memory to hold us back. While 2GB of RAM is ample for XP it's the bare minimum for running Vista comfortably, so we stuck with the tried and trusted previous version of Windows.

We rounded up a stack of memory and this is it:

• 1GB of PNY K-DIMM1GBN/6400/2-BX PC2-6400 800MHz
• 2GB of TwinMOS PC2-6400 8D25KK-TT PC2-6400 800MHz
• 2GB of Corsair XMS2 CM2X1024-8500C5/1066MHz
• 2GB of OCZ DDR2 PC2-9200/1150MHz FlexXLC Edition
• 2GB of Corsair Dominator CM2X1024-9136C5D XMS2-9136 /1142MHz
• 2GB of OCZ DDR2 PC2-9200/1150MHz Reaper HPC Edition
• 2GB of Kingston KHX11000D3LLK2/2G PC3-11000
• 2GB of OCZ DDR3 PC3-10666/1333MHz Platinum Edition

That's five types of DDR2 ranging from 800MHz to 1,150MHz and two sets of DDR3. Each set was a pair of dual-channel capable, 1GB modules, with the exception of the 2 x 512MB bread-and-butter PNY set.

This entire round-up centres around clock speeds so it's worth spelling out that the numbers we are referring to are a mixture of effective and true clock speeds. The 1,333MHz FSB of the latest Core 2 Duo processors is actually a quad-pumped 333MHz bus so our 2.66GHz CPU runs at 8 x 333MHz. DDR2 and DDR3 are both ‘double data rate' memory so you halve the stated speed to get the true speed, thus 800MHz DDR2 runs at 400MHz and 1,333MHz DDR3 runs at 666MHz.

You'll often see that memory is rated by its bandwidth, which is measured in GB/second, but this is purely a function of clock speed so it's quite easy to convert clock speed to bandwidth and back.

DDR2-800 runs at 400MHz and is also known as PC2-6400 as it has a maximum bandwidth of 6.4GB/second, while the Kingston KHX1000 has a maximum bandwidth of 11GB/second and runs at 692MHz or an effective speed of DDR3-1385.

It's also worth pointing out that no two memory modules are exactly alike, so there's no guarantee that the overclocking results we achieved will be matched by any other module. Modules that you pick up at retail might do even better, or might do worse; the phrase 'Your Mileage May Vary' (YMMV), certainly applies here.

We'll begin our testing with two sets of stock DDR2 800MHz RAM, move onto some high performance DDR2, and then conclude by taking in some new fangled DDR3, to see how it compares.

Are you sitting comfortably? Then let us begin.

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