The modules
Crucial's DDR3 line-up extends from 1GB to 12GB and ranges from £40 through to £800. The company has cottoned-on to the fact that enthusiasts, in particular, will look to run the cheapest Core i7 processor, the 920, currently costing around £230, on top of a DDR3-supporting X58 motherboard.Intel's architecture is such that the memory-controller, located on the CPU, can use three 64-bit memory channels for increased bandwidth, and that's why 3GB (3x 1GB modules) and 6GB (3x 2GB modules) have started to become popular sellers.
What's interesting to note is that Core i7 920 and 940 are limited, on some motherboards, to 2:8 ratios, meaning that DDR3-1,066 is the fastest officially supported speed (1,333MHz on Core i7 965 EE). You can push it higher by opting for a proper enthusiast-class motherboard - ASUS, Foxconn, MSI, et al - or by overclocking the CPU's 133MHz reference clock. However, every memory manufacturer will have 1,066MHz-rated modules in their catalogues.
Crucial is sensibly packaging three modules together and selling tri-channel kits of various sizes. We're looking at a 6GB set (3x 2GB modules) that run at 1,066MHz with a CAS latency of 7. The pack currently etails for £144.89, which includes free shipping.
Click on the picture to enlarge. A single module's sticker highlights a truncated specification, and digging around shows that it's specified with 7-7-7-20 timings (CAS latency, tRCD, tRP, tRAS). Command rate isn't specified, so it's a good bet that it will be 2T. What you need to take away from these numbers is that lower means more performance
The ICs are manufactured by Crucial's parent company, Micron, and we little reason why that will change in the future. iSuppli, one of the industry's analysts, places Micron 16th in the semiconductor rankings with 2008 revenue of $4.4bn. Incidentally, that's above NVIDIA's $3.4bn but below AMD's $5.9bn. Profit, though, is an entirely different story....
Back on track, the Intel Core i7's memory-controller isn't particularly partial to voltage increases and 1.5V, the JEDEC standard, is what the chip giant suggests most mainboards use. If overclocking, running much above 10 per cent higher - 1.65V - is seen as a no-no.
Crucial plays it straight down the line with a module rating of 1.5V, however, and that's why we don't see the set adorned with fancy heatspreaders; there's simply not enough build-up to justify to the extra cost when DDR3 is inherently expensive.
The usual Crucial limited lifetime warranty applies to this set, and you can find the pertinent details here.
A 3GB pack of the same-speed memory costs £82.79, but bigger-capacity sticks are always better if you're looking to keep expansion opportunities open in the future.
The question, we suppose, is what benefits does 6GB of optimised DDR3 give you over 3GB, and that's what we'll find out, but bear in mind that you'll need a 64-bit operating system to fully exploit the capacity benefits of >4GB of RAM.