As far as cache is concerned: the Intel Core 2 Duo uses shared L2 cache -- I picked the E6600 myself, primarily because it has 4MB of cache. Even if all you run is a big singlethreaded app and the 2nd core isn't doing anything, that still means 4MB of L2 available. that's a whole lot more than most of the older single core CPU's have available.
The AMD X2's don't share cache, so while pretty nice CPU's you have a penalty in that area -- one core sitting idle means that you essentially waste half of your caching ability as well.
Even though my new core 2 Duo E6600 runs at 'just' 2.4GHz, I notice a massive speed improvement over my older AMD Athlon 2800+ (single core) which ran at 2.21 GHz. The cache difference is massive though, and the speed increase is substantially higher than the 10% difference in MHz might lead you to believe.
The cheaper Pentium D's, on the other hand are junk. they were just a stop-gap measure for Intel to release while AMD was killing them with the dual core AMD CPU's and intel wasn't even close to having the Core 2 line ready for production.
(Core 2 Duo is based on the older Pentium 3 Mobile architecture, while the Pentium D is based around the Pentium 4. the P4 was a step backwards from the P3 mobiles in that the mobile chips had a much shorter pipeline and was much more power efficient (=cooler as well) than the P4 designs ever were.
The AMD X2's don't share cache, so while pretty nice CPU's you have a penalty in that area -- one core sitting idle means that you essentially waste half of your caching ability as well.
Even though my new core 2 Duo E6600 runs at 'just' 2.4GHz, I notice a massive speed improvement over my older AMD Athlon 2800+ (single core) which ran at 2.21 GHz. The cache difference is massive though, and the speed increase is substantially higher than the 10% difference in MHz might lead you to believe.
The cheaper Pentium D's, on the other hand are junk. they were just a stop-gap measure for Intel to release while AMD was killing them with the dual core AMD CPU's and intel wasn't even close to having the Core 2 line ready for production.
(Core 2 Duo is based on the older Pentium 3 Mobile architecture, while the Pentium D is based around the Pentium 4. the P4 was a step backwards from the P3 mobiles in that the mobile chips had a much shorter pipeline and was much more power efficient (=cooler as well) than the P4 designs ever were.