HyperThreding is IMHO only needed for nutburst because the chips by design are so in efficent, HT isnt in current chips because the way they did it with P4 wont work with core2/p6 cores, remmber eading an artical about it, intels working on something simlar that "may" show up in some core3(or whatever they call it) chips, but from what i was hearing all the stuff they tryed to get it working had ended up with the systems using core/pentium-m being slower, its better and easyer to just use 2 real cores then a 2nd logical unit to make a Fake cpu that ends up floging the cache trying to squeeze out some more perf.
HT was done by intel to combat catch misses and true dual core cpu's as well as to try and make better use of a VERY poor cpu design, only an intel fanboi would say that netburst is good, even intel has admited it was a bad move, hence they went back to the pentium-pro(p6) based core thats FAR more efficent and was used in ppro,p2,p3 and pentium-m chips, these chips dont need HT to respond nicely.
i alwase love it when nutburst users talk about responciveness and performance, specly when they then bring HT into the conversation.......it makes me laugh, because the only reasion HT ever came to be was to try and make poorly designed cores perform better and to give intel something to try and counter the x2's.
and 2k dosnt get along with it because it is a FAKE 2nd cpu/core, 2k3 and xp have been patched to see that its a fake 2nd cpu and use it accordingly, xp effictivly is 2k with alot of extra crap dumped on that only newberts really "need", like system restore.....HAHA if you cant fix ur own fookups mayby you should move to an os that dosnt let you fookup
http://en.wikipedia.org/wiki/Hyper-threading
Future
Older Pentium 4 based MPUs use Hyper-Threading, but the current-generation cores, Merom, Conroe and Woodcrest, do not. Hyper-Threading is a specialized form of simultaneous multithreading (SMT), which has been said to be on Intel plans for the generation after Merom, Conroe and Woodcrest.
More recently Hyper-Threading has been branded as energy inefficient. For example, specialist low power CPU design company ARM has stated SMT can use up to 46% more power than dual CPU designs. Furthermore, they claim SMT increases cache thrashing by 42%, whereas dual core results in a 37% decrease[1]. These considerations are claimed to be the reason Intel has dropped SMT from new cores.
However, some low-power chips do still use multithreading, including the PPE from the Cell processor, the CPUs in the Playstation 3, Sun Microsystem's Niagara and the MIPS 34K.[1][citation needed]
p4/nutburst chips need HT because catchmisses really hurt them, long pipes suck
At NGMA's heart is a 14-stage instruction pipeline - around half the length of 'Prescott' pipeline, the same as the old Pentium Pro, and probably in line with 'Dothan' pipeline length. Prescott's pipeline was extended to around 30 stages to support clock frequencies of 4GHz and beyond. Now that Intel is no longer targeting such high clock speeds - thanks to the heat dissipation problem - out goes the need for such a long pipeline, needed to keep the core efficient at high clock speeds.
http://www.theregister.co.uk/2005/08/23/intel_next_gen_architecture/
the articals old but kinda shows why core dont have HT, unlike p4/nutburst chips the pipes are not massivly long, 30+ stages for prescott, ewww, pentium pro/core/core2 have 14.....very diffrent tech, with far less cache misses AND even if you have a cache miss, it dosnt hurt perf neerly a much as it would with LONG pipes because theres less wait time between cache reads
). And even now with my own x2 4200+ system oc'd to 5000+ ish speeds, that old northwood still is very snappy! I sold the entire system to a friend who is still using it with a 7800gt agp w/ 1gb of ram and the thing runs great. In fact I wish I hadn't sold that northwood setup, not just cause it was my first build 