For no good reason at all I toyed a bit with two similar C2D CPUs: an E7400 with 3MB cache, and a Pentium E6600 with 2MB (that's not the C2D E6600). I set them both to 306 x 10 = 3.06GHz, which is an overclock for the E7400's 2.8GHz and a sideclock for the E6600's default 266x11.5.
I benchmarked with WinRAR, 7zip, SuperPI, and AIDA64. They ended up practically the same. Only one specific AIDA test gained +7% on the E7400, maybe due to the cache. But there's one peculiar deficit: the E7400 is -4% in 7zip decompression. Any idea why that might be?
And ignoring RAM, any thoughts on FSB vs multiplier?
PS: Aren't mobos supposed to beep when the P4 12V is not connected? At first I thought the CPU was bad.
PS2: Did you know Intel CPUs might differ in features in the same model and stepping, just with a different sSpec? This E7400 is missing VT-x.