uhmm? Hypertransport on Dual-Core Amd CPUs will have lot of bandwith, so that it should not have a big influence on the performance.
Anyway... Intels actual 'Dual-Core' technic is actually technically the same as on Dual-Xeon Boards. Except that you don't have to have 2 sockets.
So IMHO this is not really a 'big' change in technology (or technology leadersip).
on AMDs side, this is going to be slightly different. They did not only put 2 cores together on one die, no, they do share L2 Cache, what has several advantages. On AMDs side there's also NUMA.
The two AMD Opteron/Athlon64 on one die AFAIR communicate together through an HT-Link. But not the external, for sure. NUMA runs also trough this.
If you look at 'older' NUMA Benchmarks with 4 Opterons, you can see a Memory Bandwith increase from about 7000MB/s to >20000MB/s!
that was with 'external' HT-Link... with internal the distance is lower, thus allowing decreased latencies. And... it doesn't stress the 'external' HT-Link.
Then there's the power consumption, too.
Pentium EX with Dualcore 3.2GhZ (incl. HT) has got a TDP of 130Watt, meaning a Top of 172 1/3 Watt. Woohoo... new world record
i suppose it could be even higher.
if the Pentium EX consists of 2 'low power' 82Watt TDP 3.2 Pentium 4 (HT), then it could reach >200Watt...
AMDs Opteron Dualcore CPUs will be about 100Watt max.
AMDs Athlon64 Dualcore CPUs will be lower. Winchester are currently at 40Watt max, putting two of them together would result in approx. 75Watt...
and , AFAIR, there will be a 50Watt Version for Opteron Dualcore, too.
On the really 'big' machines (like crays 'red storm' project) power consumption is a major criteria.