Memory performance
We generally kick off our benchmark suite with some memory tests, and this time out the test underscore an important point.

As you can see, the Athlon XP has hit a brick wall in memory bandwidth; raising the CPU clock speed doesn't help. Although our test system has DDR333 memory, memory performance is limited by the Athlon XP's 266MHz front-side bus. In fact, the T-bred at 1.8GHz comes out a little slower than the Palomino does at 1.73GHz. I'm not quite sure why that is, but I ran this test a number of different times, just to be sure, and the T-bred was consistently just a tiny bit slower.

The Pentium 4, on the other hand, fares especially well with a 533MHz bus. Although we chose not to repeat the results here, if you look at this review, you'll see that the P4 does very well with DDR333 memory, too.

Now let's make a graph that looks vaguely scientific, so your boss won't mind if he catches you reading this at work.

Linpack shows, from left to right, floating-point performance when processing data stored in the L1 data cache, the L2 cache, and then main memory. (The processor has to step down the hierarchy of memory types and speeds as the size of the data matrices Linpack is feeding it grows.) The move from 1.73GHz to 1.8GHz for the Athlon XP boosts performance when accessing on-chip caches, but it does nothing to help once we pass about 320K matrix sizes, beyond the domain of the Athlon XP's combined L1 data and L2 caches.

Notice that once we pass matrix sizes of about 100K, every variety of Pentium 4 system in our test is faster than any Athlon XP. The Pentium 4 platform has a pronounced advantage in memory bandwidth from the L2 cache out into main memory.

However, bandwidth is only one of the two key components, generally speaking, of memory performance. The other is latency, and we haven't run any latency oriented tests here. (We will next time out, honest.) Also, memory performance is itself only one piece of the overall performance picture.