Capture One DSLR
Capture One D-SLR

Remember how the Pentium 4 platform was the fastest single CPU platform for Capture One D-SLR? Imagine if you thought you were working with applications needing 2GB of RAM and thought you would get extra performance from your PC by adding more RAM? On the Pentium4, this severely decreases your performance. The Opteron, running registered RAM, has no significant change in performance.
Photoshop Camera Raw

Even though the Athlon64 drops to PC1600, it's lower latency is what is most critical in accelerating performance. "Upgrading" your Pentium 4 from 2x512MB to 4x512MB would actually decrease performance by 33%!

Even when working with a 15 megapixel image, the Athlon 64's PC1600 memory bandwidth is still able to beat the Pentium 4 @ 2 GB of RAM.