I am debating whether to get an Q6600 or an E6850 processor. I neither play games nor do extensive 3D rendering. I have reviewed the relevant forums and benchmarks I could find - however, most of the benchmarks comparing these two processors deal either with Windows software, or Rendering/Gaming apps.

Would GNU/Linux utilities like gcc, tar, the python interpreter, etc. show a notable improvement from SMT? Which standard GNU/Linux utilities are currently best suited for SMT/SMP? If you have any qualitative /quantitaive measure to share on the performance difference, that would be apreciated as well!

Any non thread-safe code is going to cause problems (regardless of the number of cores) once you move off a uni-processor. Multi-processor systems have been around for years - the kernel will schedule on any processor it finds. Multi-core doesn't substantially change things from an application point of view.

Personally I would always go for more processors - will allow more concurrency whilst there is a non-empty run queue. Depends on your needs - it might be that you'll wind up with processor(s) waiting for work. I'm talking normal workload here, not contrived benchmarks you see in the mags.

Certainly kernel compiles can be made to "fly" on my quad server - make needs to be prodded with th -j flag, but it certainly shortens the elapsed time. But for the rest of the day, the machine is basically just sitting there waiting.

So ... "it depends".