I did a few more SPI 4M tests with my dual xeon rig, did the CDT-IV tweak i did before, and i did my own version of this tweak, final times are exactly the same.

My version "Hixie tweak ver1.0"
Step 1: Set MAXMEM to 600, and made a file 604MB large (600 as in the MAXMEM value and 4 because i'm running 4M Super Pi)
Step 2: Open up Super Pi, and select 4M, but stop that the start button.
Step 3: Open task manager, and keep copying the same 604MB file into THE SAME FOLDER, until System Cache and Available memory figures match each other.
Step 4: Close everything, and run Super Pi.