Obviously I cannot **prove** my negative experiences with hyperthreading, but I have still seen time and time again, even on some not-so-old CPUs, that partitioning has been severely damaged on those machines, requiring data recovery, partitions *deletion* (not just formatting), and reinstall everything from scratch (or otherwise, just "normal" Windows-stops-working syndrome). Same symptoms, same CPU tech.
A client of mine has three computers, ALL of which had hyperthreading CPUs (a P4 and 2 Atoms), and they have ALL of them broken down -- two of them in the typical manner that I have come to associate with hyperthreading which is that some data-corruption damage to Windows occurs requiring format and full reinstall. After some months of ongoing and continual breakdowns, which I predicted to the client unless she changed CPU, she eventually agreed to have a new custom-built computer.
I have installed W7 on the second, and we will see if W7 can manage hyperthreading and avoid the instability. (?)
The third I have so far been unable to fix.
Like I said, maybe Intel has ironed out the bugs with NuHyperthreading, and I _have_ also seen some machines with hyperthreading CPUs that work perfectly well -- and it's possible that certain motherboards are to blame rather than the CPUs. But as the chipsets on these boards are designed for these CPUs anyway, does it really make much difference ?
My ongoing hands-on experience has led me to a very, very deep distrust of hyperthreading, and I would NOT be at all surprised if I were to see clients' i7-based rigs completely and similarly broken down in future.
Comparing with equivalent non-hyperthreading CPUs is somewhat difficult, because the number of cores at any given date will be different -- but a CPU with X physical cores will at equivalent clock rates and everything provide better performance than one with X/2 physical and X/2 virtual cores simply because there will be no software-based virtualisation managing any extra cores during every single clock cycle --- BUT hyperthreading CPUs typically have up to double the number of apparent cores than non-hyperthreading ones of the same generation.
I think that most people automatically assume that when Windows breaks down it's something wrong with Windows -- which likely explains why you never see many people complaining about fundamental hardware instability. Of course, most people are incapable of detecting it when it occurs, for them it's just Windows. Another reason is that the specialist benchmarking sites that compare various CPUs use newly installed hardware -- whereas the problems I have seen involving hyperthreading CPUs all seem to surface after some months of use, instead of immediately.
Anyway, given that ALL i7 CPUs use hyperthreading, I personally would not touch any of them with a 10-foot pole ; and I would therefore personally wait for triple-channel DDR to be available with other CPUs before adopting this new standard ... the first triple channel -capable 6-core AMD CPUs are scheduled for the end of the year as far as I can see (which might mean early 2010 given the history), and I do not know if Intel has any plans to sell CPUs *with* the triple channel controller but *without* the hyper-threading.
Anyway, Intel has managed to screw AMD yet again, by simultaneously reintroducing the unstable hyperthreading *and* this new method of putting the memory controller on the CPU instead of the motherboard *and* winning the race to put out the first triple-channel DDR3 hardware. Talk about a triple whammy
Intel have set the bar so high now, that AMD are going to have HUGE difficulties even to just catch up :/ -- but I would personally STILL buy AMD because stability is generally guaranteed with AMD, whereas with Intel it can be pot luck.