Closing Thoughts

Closing Thoughts

There are two key teaching points in this article.

First, is that you should not buy a fast CPU without the fast memory to support it. In the first group of benchmarks, a P4 2.8 GHz is able to beat an identically configured P4 3.0 GHz system if the 2.8 is running Corsair XMSPro 3200-LL RAM, in certain applications. It's worth noting that we weren't running bottom-of-the-line RAM in the P4 - it was still Crucial brand memory.

Second, it is clear that those who complained about the Registered DDR requirement/support of the Athlon64 FX did not fully understand the technology, or they did not consider pushing high-performance computing envelope. Registered DDR is critical for ensuring that performance remains stable despite a large number of installed DIMMs. With "normal" CPUs such as the Pentium 4, Athlon 64, or Athlon XP only two DIMMs (4 banks) should be installed for maximum performance. Adding additional DIMMs can in fact reduce performance as we have shown. Nobody would agree to spend more money on their system only to have it run slower. It should be noted that these are not only our isolated observations, but discussions with the motherboard and chip engineers confirm this scenario, one even suggested that some motherboards (though not their own) would be unstable or would not run at all when challenged with more than 4 memory banks occupied.

If you are currently at 2x256MB on your P4 desktop and feel that more RAM is necessary, you can consider an additional 2x256MB for a total of 4 banks. Alternatively, you would likely see higher performance with 2x512MB and replace the existing RAM. Those of you needing more than 1GB of RAM, will either have to consider 2x1GB DIMMs available in quantity only in PC2700 speeds, or move to a Registered DDR PC3200 setup and run 4x512MB Corsair XMS 3200-LL.

It's disappointing that despite the immense press coverage of the i875P and Athlon64 platforms, no one has stopped to evaluate the performance issues of greater than 4 banks of memory in a set of real-world tests. CacheMem and other synthetics cannot tell the story that a few real-world tests can show. This is particularly true because RAM is getting cheaper by the day, and it is not uncommon or difficult for users to buy more than a gig of RAM, expecting better performance. Moreover, it is particularly unfortunate that many motherboard manufacturers continue to advertise their boards with maximum memory capacity rather than maximum memory capacity at full speed. ASUS does provide documentation in their manual regarding the maximum recommended memory configuration at a given speed. We commend ASUS for their interest in keeping the customer informed about the strengths and weaknesses of their products.