Activity on odd numbered cores

Hello all...

I upgraded to Snow Leopard and have noticed an interesting phenomenon. When running Activity Monitor and using the cpu activity or cpu history windows, I see activity on odd-numbered panes only. I.e. Core 1, 3, 5, 7, …up to 15. I only see evidence (In apple activity monitor) of load on even numbered cores when the machine is totally stressed with an app like bresink System Load, or 64 bit hypertheaded applications. Even then, the load on even cores are lower that those on odd cores. This is confirmed with Bresink hardware monitor as well as using the activity monitor.

When I boot back into leopard, which I have installed on a separate drive; I see equal activity on all 16 cores (or all panes of the cpu monitor/activity monitor) as usuall.

1. Has anyone else who has upgraded from Leopard to Snow Leopard noticed this change in behavior?
2. Is it normal?
3. Can anyone explain which core numbers (1 through 16) belong to which cpu (A/B)?

Thanks!