Triple-Channel DDR3 Final Thoughts

Don't make the mistake of thinking DDR2 has anything in common with DDR3. Unlike DDR2 memory kits, which generally have a dependency on speed over latency, DDR3 reserves itself to performing better with lower latency kits than those of higher speed. The architecture between the two standards is quite different, as we've detailed in our DDR3 RAM: System Memory Technology article. On top of these differences, DDR2 memory kits never made it out of dual-channel configurations and are not compatible with Intel's triple-channel motherboards.

The new tri-channel configuration for the Intel Core i7 CPU & X58-Express Platform certainly has its benefits, but some of the old traditions are lost in the new standard. Because of the high penalty for round trip cycles, latency offers a bigger performance incentive than clock speed. Sure, it's nice to reach 2400MHz or faster with a DDR3 kit, but if it takes one or two extra strobe cycles to generate that speed then the benefits are lost. This essentially divides triple-channel memory kits into the following preference order:

1. Low Latency (CL6 or lower) + High Speed (1600MHz or faster) = Most Preferred
2. Low Latency (CL6) + Standard Speed (1333MHz) = More Preferred
3. Standard Latency (CL7) + High Speed (1600MHz or faster) = Preferred
4. Standard Latency (CL7) + Normal Speed (1333MHz) = Acceptable
5. High Latency (CL8) + High Speed (1600MHz or faster) = Less Preferred
6. High Latency (CL8 or higher) + Low Speed (1066MHz or slower) = Least Preferred

Memory module profile can often make or break a system build. Computers with large CPU-coolers may not combine well with RAM kits utilizing large/tall heatsinks. Additionally, low-profile and HTPC computer systems may not offer the clearance if there are other components located overhead (such as an optical drive).

As the Far Cry 2 benchmark tests have shown, in a popular game with realistic settings and hardware the performance difference between a low-speed triple-channel DDR3 and high-speed kits is barely 3 FPS. If you're a gamer looking for faster graphics, my advice is to invest the money into a better video card. If you're running an audio or video editing system, look for low-latency memory with a fast storage drive (such as SSDs). While there is some small degree of performance to be gained by faster memory modules, the real argument for high-speed RAM is the added overclocking headroom.

If there's a decision between 3GB triple-channel DDR3 kits, and those of 6- or 12GB density, the answer is simpler. If you use a 32-bit Operating System such as Windows XP or Vista, you're limited to 4GB total. You might think that there's a 1GB gap between the 3GB supplied and the 4GB limit, but if you're using a video card with a large frame buffer, this amount gets added into the limit and fills the gap. If you're using a 64-bit Operating System, such as 64-bit Windows-7 or Vista, my advice is to use as much RAM as allowed by the motherboard but not more than you'll realistically use.

It's all about tailoring your needs, because if you install 12GB of DDR3 and your workload never utilizes more than 4-5GB, then the unused memory becomes a penalty for data strobes through the system. Use the Windows Task Manager to monitor your memory usage, and if you're within 80% of capacity when workloads are at their heaviest, then it's time to install more RAM. This was especially true in our Photoshop CS4 tests, which illustrated how high-density memory improves application performance in memory-hungry programs.

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