The FSB being what it is, yes, they suffer somewhat without L3. Straight CPU-bound tasks work well (hence Virtual PC's notable performance improvement, as well as Cinema 4D), but mixed tasks probably starve the CPU for data. I'd still take the 1.8s over this MDD's original 1.25s any day, though. While not everything may run as fast as I think it should, nothing runs slower.

FWIW, MP Tasks seem to work fine on it, even though Sonnet says multiprocessing is not supported on 9.2.2. However, these are 7447As, so it could be something specifically about the 7448.