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What about hyperthreading?

March 17, 2005 at 19:02:49
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From what I have heard, hyperthreading can only yield about 15-20% more work than a non-hyperthreading machine. So when I look at it as say 120%, if the dual core Intels have hyperthreading capabilities, does that mean that you will yield in terms of work rendered, 240%?

YO


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#1
March 17, 2005 at 21:16:53

I always thought that hyperthreading is only any good with programs whose code were written to support it?


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#2
March 17, 2005 at 21:34:16

I personally Highly doubt that. They said when Hyper-thrading came out it was suppose to be almost as good as dual processors and later test found out when things supported Hyper-threading that wasn't the case at all. Hyper-threading for the most part was a waste, because the majority of programs don't use it and when some programs did have hyper-threading supported there wasn't that much better diff in preformance.

Dual core processors will be like what dual Channel is to ram. Meaning allowing more traffic to flow to cache without a lot of backlog. But you will see hardly any diff between a dual core processor and a single core process using 32 bit programs. You will however start to see a noticable diff between a dual core processor and a single core processor in 64 bit programs though becaus 64 bit is more cache hungry then 32 bit is and by providing more lanes of traffic on dual cores it will feed a lot of the 64 bit programs needs without any backlog.


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#3
March 17, 2005 at 23:02:42

Isn't it ironic you can't spell the word "Hyperthreading" without putting some hype in there.

Most apps out there right now are not multithreaded, so there is little or insignificant gains to most users at this time.


B4 you criticize a bigger man, walk a mile in his shoes. That way, you're a mile away, and you have his shoes.


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#4
March 17, 2005 at 23:33:25

Yeah, that's all it is, is Hype. That's why AMD's CEO stated they will not have anything similiar to Hyperthreading in their future processors because not a lot of programs use Hyperthreading in the first place.

I hope AMD does boost it's cache to 2mb before Windows 64 becomes mainstream because 512kb of cache on 64 bit programs isn't going to cut it for very long especially when 64 bit programs get more advanced. Intel Pentium 64 bit 6xx with 2mb of cache vs Intel Pentium 32 bit 5xx with 1mb of cache run neck and neck when it comes to encoding and burning benchmarking in 32 bit mode. Now Windows 64 bit is a totally diff story. Intel Pentium 64 bit 6xx with 2mb and AMD Athlon 64 512kb in benchmarking in encoding and burning was almost a lop-sided affair when it comes to encoding and burning because those types of programs need as much cache as they can get. That's why I hope AMD slaps at least 1mb or 2mb of cache standard on it's single and dual core systems. Intel did on put 2 mb of cache on it's single core and will on its dual core. I just can't see an AMD Athlon 64 bit 512kb a dual core processor.



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#5
March 18, 2005 at 00:54:44

A CPU has multiple resources (adders, etc). In a non-HT cpu, it can only execute one thread at a time. Not every resource is used. In a HT cpu, it can execute two threads at a time (the un-used resources can tackle on the 2nd thread).

This is helpful for both multi-threaded programs, as well as multi-tasking environments (ie: windows). Each program is a single thread, and thus thus a HT-cpu can handle two programs. It's like when you want to check the stability of an overclock...you run two copies of prime95, and tell each copy to either use cpu-0 or cpu-1.

What is Hyperthreading?

I would hate to see AMD try to copy intel's strategy...the two giants have always tried to do things differently (that's why they're not directly comparable...apples and oranges).

My sister has a p4 2.4 hyperthreading cpu, and her computer works quicker than my bro's p4 2.4 non-hyperthreading computer. I get so frustrated working on my bro's computer, that I sometimes get up to grab a drink or something while waiting lol.

Hyperthreading doesn't have such a huge impact, but there is a noticeable difference. Finishing 15-20% quicker is nicer too


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#6
March 18, 2005 at 01:40:49

The problem with Hyper-threading is how it is compared. The AMD Athlon 64 3200+ vs an Intel Pentium 4 3.2ghz in a pc game using mutlithreading did help the Pentium 4 out, but the AMD still beats it, but not a whole lot.

Now if you are talking a program that uses mutlithreading then there is almost no contest vs the AMD, because the Pentium 4 with hyperthreading will beat it hands down in most program apps that aren't games or use lot of graphics.

Now Hyperthreading would be better if it was automaticly controlled where it would notice a multithreading progam running and instantly turned itself on. But when you aren't using multi-threading or when the mutlithreading program isn't active then it would automaticly go into a standby state and allow you to use the whole processor for other things. That's the only thing that I don't get about Intel not doing something like that, because everyone knows when Hyperthreading is turned on it effects everything that isn't multi-threaded and in order to shut it off you have to do it manually.


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#7
March 18, 2005 at 07:53:45

then ontop of that you have to have windows xp or some version of linux to use it.

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#8
March 18, 2005 at 14:45:57

Whould someone just anwser the last sentence YES or NO?

"From what I have heard, hyperthreading can only yield about 15-20% more work than a non-hyperthreading machine. So when I look at it as say 120%, if the dual core Intels have hyperthreading capabilities, does that mean that you will yield in terms of work rendered, 240%?"

YO


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#9
March 18, 2005 at 16:07:29

I'm saying NO.

Based on past hype from intel.


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#10
March 18, 2005 at 16:37:34

Check out tom's hardware video on HT tech, it shows a HT 3ghz beating a 3.6ghz without HT. Even if programs are not coded for HT you still benefit when your working in a MULTITASKING enviroment, it takes the load off the cpu cause one app does not disrupt the other, meaning rendering a movie and playing a game will not hurt preformance. I think Intel knows what its doing.

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#11
March 18, 2005 at 17:06:59

But dual core chips will be way better than getting a hypertreading, only in the 64 bit enviroment. I say that because you wont see it on 32 bit unless you are running a server

Mod it till it bleeds


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#12
March 18, 2005 at 20:17:19

The main reason for H/T was to sell more Pentium 4 processors. I mean you look at what they say about H/T on their website and if you didn't know any better you think it was the next best thing from a dual processor system, but it isn't. Sure it helps with multi-threading programs but it's not even close to having dual processors. If I was doing a lot of mutl-tasking all the time, I would rather just shell out some extra cash and get a dual processor system.

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#13
March 18, 2005 at 21:08:28

Q: - "From what I have heard, hyperthreading can only yield about 15-20% more work than a non-hyperthreading machine. So when I look at it as say 120%, if the dual core Intels have hyperthreading capabilities, does that mean that you will yield in terms of work rendered, 240%?"


A: - Theoretically you can say YES but practically am gonna have to say NO! too.


"There are some performance arguments on computers that have multiple CPU's with HTT enabled. The claim is that depending on the operating system for example Windows 2000, NT which are already multiprocessing aware but not HTT aware. For these OS the machine will only see two processors per physical CPUs.

Since the scheduler doesn't realize the connection between the virtual CPUs, it can end up doing a worse job than if you had never enabled hyperthreading to begin with.

Now consider a dual-hyperthreaded-processor machine. There are two physical processors A and B, each with two virtual hyperthreaded processors, call them A1, A2, B1, and B2. Multiprocessing on a single CPU.

Suppose you have two CPU-intensive tasks. As far as the Windows NT and Windows 2000 schedulers are concerned, all four processors are equivalent, so it figures it doesn't matter which two it uses. And if you're unlucky, it'll pick A1 and A2, forcing one physical processor to shoulder two heavy loads (with each probably run at something between half-speed and three-quarter speed), leaving physical processor B idle; completely unaware that it could have done a better job by putting one on A1 and the other on B1.

In case HTT won’t help, it will actually slow the computer down. Windows XP and Windows Server 2003 are hyperthreading-aware. When faced with the above scenario, those schedulers will
know that it is better to put one task on one of the A's and the other on one of the B's.

Another discussion on HTT deals with the Cache Memory and in this case, the problem will be there even if the operating system is hyperthreading aware. In the following example, HTT ends up a net loss.

(For example, if you have four tasks, two of which rely heavily on L2 cache and two of which don't, you'd be better off putting each of the L2-intensive tasks on separate processors, since the L2 cache is shared by the two virtual processors. Putting them both on the same CPU would result in a lot of L2-cache misses as the two tasks fight over L2 cache slots.)"

See study on HTT for more.

B4 you criticize a bigger man, walk a mile in his shoes. That way, you're a mile away, and you have his shoes.


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#14
March 19, 2005 at 04:35:42

Now we are getting somewhere. Thanks for the two "NO" answers guys.

And Saber, that write-up explained alot of stuff that I didn't fully understand. Now it's just a matter if storing it into my memory banks so I don't forget. lol!

Thanks guys for the input!

YO


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