Talk:Hyper-threading

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[edit] Plagiarism obvious in this article.

Someone, without even bothering to rephrase lines, has copied chunks of text from a website. The text is primarily:

It's all taken from, in its almost exact state, from HyperThreading Technology - Overview. There may be more plagiarism I didn't pick up. Stiles 20:20, 18 March 2006 (UTC)

that need to be fixed very rapidely by

• changing it's state from plagiarism to fair use...that means citing the sources and simiilar thing
• then remplacing it...
• or asking the autorisation to the website

by the way the adress changedd:http://www.osdcom.info/content/view/30/39/

we must also check the dates in order to know who has copied(that could also be the website...)

213.189.165.28 09:38, 16 April 2006 (UTC)(only for the comment)

Amusingly, the OSDEV article contains text copied from the Ars article on HTT. For example, the text

appears in both articles (albeit the OSDEV version introduces a number of grammatical mistakes, and doesn't include the diagrams the text is referring to). As for the anon user's suggestion we need to fix this "rapidly", I don't see the rush—I'll remove and rewrite the copyvio'd material when I get a chance, if no one beats me to it. Neilc 18:16, 16 April 2006 (UTC)

I don't think plagiarism or a violation of copyright in Wikipedia content is so "obvious" here. Wikipedia's changes are old and have been accumulating over a very long period of time. Here's an example, if you'll excuse the verbiage...

Looking back at the history, the last sentence of the first paragraph in Wikipedia achieved its current form on 24 July 2003, and the first sentence got reasonably close in the same edit:

[Never mind the grammatical errors now. =) ] On 7 September 2003, we get the content of the second sentence, though still no grammar, and on 9 September, "simultaneous multithreading" is corrected:

On 10 January 2004, the broken grammar is finally fixed, and on 8 December we get the first mention of "Hyper-Threading Technology":

but it is removed on 24 May 2005; the opening words are changed to include "Technology" later that day:

This, of course, is the version that matches that appears on the OSDEV Web site.

Of course, the OSDEV Web site was recently revamped, so all of their articles are dated 26 March 2006. This makes it hard to conclusively demonstrate that the content in Wikipedia is older, and that it's the OSDEV author who "borrowed" it. But the fact that Wikipedia content took form gradually over a two-year time period makes it hard for me to believe that someone really "copied chunks of text from a website" into Wikipedia. bert 19:18, 20 April 2006 (UTC)

It looks nobody is able to prove the suspected copyvio because the site in question does not support a page history. If there's nothing new in the next days I'll remove the obvious wrong copyvio tag. It really looks more the OSDEV author used text from various other sites fo his own text. --Denniss 18:00, 25 April 2006 (UTC)

I've gone ahead and removed the tag, as it's been sitting around for a while (judging from this discussion). The OSDCOM site was registered in 2004, and the text in this article dates back to 2003, so there really isn't much of a case for a copyvio. Zetawoof^(ζ) 02:31, 10 May 2006 (UTC)

[edit] Contradiction

Hyper-Threading works by duplicating certain sections of the processor—those that store the architectural state—but not duplicating the main execution resources

is is also say that :

allowing multiple threads to run simultaneously

how can the processor EXECUTE 2 process or threads at once with only one execution unit...that's impossible

the reality is that:

• technicaly they duplicated "certain sections of the processor—those that store the architectural state—but not duplicating the main execution resources" allowing the processor to make a context switch in almost no time
• there is a huge marketting going on Hyper Threading saying that it behave as 2 processors

allowing the operating system to schedule two threads or processes simultaneously

mabe an expert could help me on this point because i have realy no idea

that's why i called for an expert,i doesn't know evrything on hyperthreading and it's specific design so i prefer beeing prudent and call an expert rather that make errors...

WE MUST ALSO SEARCH FOR OCCURENCES OF HYPERTHREADING IN ORHERS ARTICLES AND FIX IT ALSO IN SOME OTHERS ARTICLES —Preceding unsigned comment added by 213.189.165.28 (talk)

There's no contradiction. Hyperthreading allows the processor dispatch instructions from two different threads to the processor's execution units. This is not the same as a very cheap context switch: the processor is capable of executing instructions from multiple threads simultaneously (by dispatching those instructions to different execution units). See the Ars article on HTT for more information. Neilc 18:11, 16 April 2006 (UTC)

understood,i'll read this and then if i still have question i will ask here

213.189.165.28 22:35, 16 April 2006 (UTC)

By the way i prefer over-reacting that doing nothing(discuting endlessly in the talk page,that kind of behaviour can lend to big mistakes such as what i've done but in another hand it permit changes,for example once evryone was talking endlessly on the talk page about a problem in a page(windows vs linux) i proposed a new design and nobody replyed and now my design is still there(and improved because it needed a lot of improvement...)),another example is the copyright violation that was signaled ONLY in the talk page and so not fixed(another fact is that users must take care themselves of this kind of task because of the low percentage of admin between all the wikipedia editors)

But i'm sorry to have made such technical error error...lol and thank a lot for the link!!! 213.189.165.28 22:35, 16 April 2006 (UTC)

[edit] Hyper-threading related security weakness

Here is a paper that attempt to document data leaks related to hyper-threading. [1]

I think the security link in the article should be removed (or explained). It's bunk. -- Mikeblas 08:42, 31 December 2005 (UTC)

It's completely real, and somewhat terrifying for certain types of multi-user situations. Suppose there is a hospital computer that lets people phone in to get the results of AIDS tests. Suppose that the records for positive and negative results are a bit different in size or layout. Suppose an employee wants to know the status of someone, perhaps a coworker or a potential lover. Obviously, the employee is not authorized to view medical records for this purpose. The employee could use cache misses to observe what happens when the patient's data gets added to the system. While the technique is not 100% reliable, it can be good enough to cause problems. 24.110.60.225 21:24, 1 January 2006 (UTC)

This is also a covert channel. It punches a hole right through the mandatory access control systems that are intended to stop spies from walking off with more info than they can memorize. 24.110.60.225 21:24, 1 January 2006 (UTC)

Cache misses aren't determnistic or predictale enough to reliably get the information. It's simply too abstract and indirect in order to be of any real threat. Has the alleged exploit ever been demonstrated in working code as a test? The premise is just silly; it's not specific to hyperthreading, and the flawed reasoning could be applied to dual-core proessors (those which share a level of cache) or even disk drives. -- Mikeblas 23:58, 1 January 2006 (UTC)

You're not paranoid enough. This kind of stuff has been done, and has led to password compromise. Dual-core processors are indeed a danger. Anything shared can be a danger, though some things are worse than others. Another good example is CPU usage. A properly secured system does not allow low-security processes to run slower when high-security processes are active. This could be done with a dummy high-security process that runs if the real high-security process has nothing to do. The mere existance of an activity might reveal insider info that could be abused for stock trading or leaking word of military actions. 24.110.60.225 02:25, 3 January 2006 (UTC)

This has nothing to do with your personal evaluation of my paranoia level. Let's stick to the facts: can you cite a reference or an example of the password snatching you've offered as an example? Or examples of systems which handle military actions or stock trading which also host abitrary guest processes? -- Mikeblas 04:24, 3 January 2006 (UTC)

Look it up yourself. Some details to help you: I believe it was a DEC minicomputer. The password was placed across a page boundry. The password checking code would stop at the first mismatched character. By moving the password and observing execution time of the password checking routine, one could greatly reduce the guesses needed. You'd only need to guess one character at a time. So, to have an example with simple math, guessing a 5-digit numeric password would go from 100000 choices (50000 average guesses) to 50 choices (25 average guesses). Timing attacks are a time-tested part of breaking security; messing with cache misses or TLB misses is a form of timing attack. Check out the side channel attack article, which specifically mentions cache misses. Note: I haven't yet edited that page, and I did not place the original mention on this page either. The military certainly does care about multiple security levels on a single system; typically this is not authorized, in part because of problems like the one discussed here. Nobody would mix TOP SECRET with UNCLASSIFIED, but mixing two adjacent levels would often be useful. The stock example does not involve trading computers. Rather, it involves business operation computers whose activity reveals something of interest to a stock trader. Perhaps the date of a major activity is revealed before it is properly announced. Trades based on such info could be considered illegal insider trading, and could be harmful to some of the stockholders. 24.110.60.225 05:14, 3 January 2006 (UTC)

I will, if you can give me one more hint: which DEC minicomputers use hyper-threading-enabled processors? -- Mikeblas 05:55, 3 January 2006 (UTC)

[edit] Hyper-threading architecture

I thoat hyper-threading was an hardware implementation of thread switching processus who takes a lot of cpu time

[edit] Clairvoyant Wikipedia?

From the article: "The real question is not whether Hyper-Threading returns, because it will, but how it works." Says who? While this may be true, predictions about the future must never be presented as facts. -- Grahn 17:26, 19 December 2005 (UTC)

[edit] cache sharing

Why did User:The1physicist delete the contribution about cache misses? Are the cache misses really less substantial than the effect the replay system has? Even if the issue is the replay system, the Intel documentation says that cache misses are one of the events that invoke the replay system. Is there any denying that cache misses (e.g./entirely* because of capacity and collisions) will be more frequent when the cache is shared between the two threads? -- Mikeblas 01:34, 3 January 2006 (UTC)

I deleted it because it isn't true. Yes, running two threads will result in more cache misses, but your overall throughput is still higher. Cache misses do invoke the replay system (among other things), but cache misses are not responsible for decreasing performance. As proof, look at the two benchmarks here. Hyperthreading got its bad reputation from the abysmal performance of the Northwood core. However, Prescott's hyperthreading has been vastly improved. As the second benchmark attests, the Prescott CPU has an increase in performance despite massive cache misses.the1physicist 21:37, 6 January 2006 (UTC)

Can someone add which processors have hyperthreading?

[edit] codename

HT was codenamed "Jackson Technology"

[edit] Needs disambiguation or explanation of difference from AMD's "HTT" or "Hyper Transport"

Not qualified to write it just know it needs to be done. When I look up HTT, I'm expecting an explanation of AMD's Hyper Transport, which is listed on Atlon 64s and relevant motherboards as HTT. It has something to do with AMD's version of frontside bus. Cheers. —The preceding unsigned comment was added by Mlhwitz (talk • contribs) 15:06, 20 February 2007 (UTC).

[edit] Requested move

Correct title should be Hyper-Threading (currently a redirect here), not Hyper-threading. This is the name as used by Intel, and in fact as used repeatedly throughout this article. If there are no objections, I will move it in a few days. — Aluvus t/c 00:02, 14 March 2007 (UTC)

Well, I think moving the article to Hyper-Threading Technology would be more appropriate, as the article states it is the official brand name. Saxbryn 11:21, 18 March 2007 (UTC)

[edit] Hyper-treading is not an Intel trademark ?

The single expression "Hyper-threading" does not appear as such in the lists of trademark nouns on the Intel Website. Is there any reference or evidence for the first sentence claming that it is an Intel trademark ? Intel does not claim it.

See: intel trademarks in english and in french —Preceding unsigned comment added by Jp78450 (talk • contribs) 09:52, 29 October 2007 (UTC)