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Whats is Hyper-Threading (HT)?


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it lets you attach yarn to a needle at damned near warp speed.

but seriously. it makes the core of the cpu look like 2 to the os by creating two threads of tasks (like a board thread more or less) so if one is idle because it's weaiting for data from ram or hd the other can be processed. that's why the pentium extreme with 2 cores and ht looks like 4 cpu's to the os.

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Essentially, Hyper-Threading Technology presents itself to modern operating systems and applications as two virtual processors. The processor can work on two sets of tasks simultaneously, use resources that otherwise would sit idle, and get more work done in the same amount of time.



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Hyperthreading is a technology which allows the computer to be working on more than one program (called a thread) at the same time. This differs from the traditional concept of "multi-tasking" because of the following: whereas in a multi-tasking operating system (Windows, Linux, etc.) it appears that multiple programs are running at the same time, they're really not. What's happening is the computer is working on one program for 1/1,000th of a second, then it switches to another and runs it for 1/1,000th of a second, then it switches to the third, etc. So, typically only a few dozen programs are running so each of them receive a large amount of the timeslice per unit time. That makes it appear like they're all running at the same time.

What HyperThreading does is actually run more than one thread at the same time. This has an advantage over single-thread machines (ones without HyperThreading--including AMD's chips), because it is recognized that even in running the most optimized bits of code using all of the resources today's out-of-order execution engines can throw at the it, there are still unused functional units within the processor core. These unused functional units could potentially be used by a second thread. Not always, but potentially. Even if the leftover units are only able to be used 10% of the time, that's a 10% increase in performance.

HyperThreading typically doesn't add much to most code, and it usually eats some overhead to maintain (internally, the operating system must keep track of where each thread is, where it's running, how long to schedule, etc.). It's generally a wash. But, there are instances where it provides significant performance increases (70%+ increase), and other instances where it hurts performance (by 30% or more).

HyperTransport is a bus technology. It is used to transfer data from a chip to other chips or other parts on the motherboard. HyperTransport is multi-ported, meaning that it can be operating several buses simultaneously at full bandwidth.

Generally speaking, a faster FSB speeds up everything. Faster processors only take you so far because nearly everything processor does is fed by external sources, thereby requiring the bus.

Both AMD and Intel have merits. Intel is generally accepted as the industry leader in sales volume. And historically Intel has directed the industry. However, with AMD's AMD64 technology (Athlon FX, Opteron, and X2), that has changed. Now AMD is guiding Intel (Intel implemented AMD64-compatible technology in their hybrid 32-bit/64-bit chips).

- Rick C. Hodgin

Hyperthreading is a latency hiding technique. While you may have a bunch of different programs open at once, the processor executes them one at a time. The scheduling is done very rapidly and the processor switches from task to task very quickly, so it looks like all of those programs are running at once when the processor is actually working on only one at a time. Hyperthreading allows the processor to work on two at a time, by allowing portions of the processor that would otherwise be idle to work on the second thread. That sounds good in theory, but for a number of reasons (contention caused by shared resources, and lack of software support mostly), it hasn't really worked out in practice.

Lastly, Hyperthreading is the ONLY thing that saved Prescott from making it obvious that it was a horrible CPU. If HT was not implemented in the Pentium 4, even Dell users would realize that the GHz idea is a myth and that their 3GHz Intel is slower than a 1.8 GHz AMD64 3000+. :)

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I would go with the AMD 64 because it's a better processor, and plus it's a new system as opposed to the refurbished Pentiums.

HP/Compaq Pavilion A839N AMD Athlon 64 3400+ / 512 MB DDR / 160GB HDD / DVD

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