Single Core mode faster then Dual Core mode?

[gotest]

Single core appears to be faster for a lot of games I have tried.
SSBB-DC mode faster (Runs at full speed on this computer with DC on, but only on brawl mode, SSE does lag for me) 30-60FPS DC 40-60SC (full speeds are harder to reach though)
SSBM-DC faster 40-60FPS DC, 20-35FPS SC
Super Paper Mario-Dual core faster but hangs for a while when flipping (Game is fully playable in Single core mode, I only got one hang in the game and that was in Chapter 3-4 when I acquired a key. DC mode will make the game randomly go really fast then slow back down) 20-60FPS SC 30-60FPS DC
Paper Mario TTYD-Single core faster 20-60FPS SC 15-50FPS DC
NSMB-Single core faster 40-60FPS SC 20-35FPS DC
Starfox Assault-SC faster 50-60FPS SC 30-45FPS DC
WW-SC faster 8-30FPS SC 6-25FPS DC
FFCC (GC)-Single Core 15-30 SC 10-22 DC
Deadly Creatures-Single core 12-20SC 10-17DC
SMG-Single core 25-40SC 18-26DC
SMG2-Dual core (not sure yet I just got it and haven't been able to test it much) 29-44DC (only tested DC)
ZTP (GC)-Single core 5-30SC 4-24DC
Metroid Prime (GC)-Single Core 10-45SC 7-39DC
Muramasa The Demon Blade-Single core 50-60SC 45-57DC
Pokemon Colosseum/XD-Single Core 20-40SC 11-29DC
LoZ FSA-Single Core 30-59SC 27-52DC
The FPS calculations were on my AMD Anthlon 64 3800+ on Rev5612 using DX9 and DSP-HLE, if you need my settings I can post them. my brother is always using his computer so I can't test it much.
All of these games have been tested on two computers, mine, and my brother's (Intel Core 2 Duo E8400, Nvidia 8800 GT, WINXP x32, 4GB ram).
Did dual core mode break or something? (I have tested 4710-5612 all the same results)