TMPGEnc 3.3 Xpress
With TMPGEnc 3.1.5.8, we encoded a 10 minute 16 second DV file to MPEG-2 format in 720x576 with an average bitrate of 4500 Kbits and in two paths. The video preview display is activated during this test and the DV file is decoded via a codec Mainconcept, which is faster than the decoder in TMPGEnc.

Intel dominates here even if the performance gap is less than with dual cores. We noticed, however, that the gap is only significant when there is HyperThreading, which means a $999 CPU.
DiVX 6.1 & VirtualDub 1.6.11
We compressed the same video as in TMPGEnc in Fast recompress mode, via DiVX 6.1 CODEC, in one path with an average bitrate of 1500 Kbits /s, b-frame and with best quality encoding performances. The video preview display is activated during this test.

In the 6.1 version; DiVX finally integrates multi-thread optimisations and it can definitely be seen. Dual core processors are in the lead, and AMD who isn´t too strong with mono-cores takes the lead.