gamerk316 :
cdrkf :
jdwii :
I'll only say something if Amd pulls the same stunt Intel pulls with SMT. As its basically free and built in the design anyways.
Well I'm not sure I'd call Intel's policy of offering chips without SMT a 'stunt'... yes it's included in the core- however it *does rely on hardware* to duplicate the threads. Is it not possible that disabling HT could allow them to salvage some parts with poor yields?
Even if not- the way I look at it, a lot of software doesn't benefit from more than 4 threads, and HT threads are weaker than full cores. So the i5 makes a lot of sense- as you're basically getting the full chip for a lot less money. 9 / 10 times that works out as better value as you don't suffer a performance loss because of it.
I will point out performance losses due to SMT is downright rare now; the OS is aware of SMT/HTT and tries to handle thread allocation so that you don't have to threads stall.
I'm not suggesting having SMT slows anything down anymore- what I'm saying is that once you get over 4 threads on a quad core, the additional performance of the additional threads is quite a bit less than that of a full core.
That means that, even in fully multi threaded scenarios with perfect scaling, an i7 with it's 8 threads is not *twice the speed* of an i5 with 4 threads. It usually depends on the type of code being run but in some situations you may get 10% extra performance, in other you might get 50%. You'll never get double though.
So for a product differentiating exercise, the i5 usually represents good value- as you have the full *hardware resources* at your disposal, just limited to 4 threads. Usually the cost reduction is more than the loss of performance. I agree though, at no point would I expect the i5 to be faster than the i7 if the two are clocked the same (at best the i5 can be expected to match the i7).
What I'm more interested though is if it's possible there is a technical yields based reason for dropping SMT on the i5 (i.e. that allows salvaging of otherwise defective dies) or if it is purely a marketing decision?