Talk:Central processing unit

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	Central processing unit is a former featured article. Please see the links under Article Milestones below for its original nomination page (for older articles, check the nomination archive) and why it was removed.
	This article appeared on Wikipedia's Main Page as Today's featured article on March 4, 2006.
Article Milestones Date Process Result December 21, 2005 Peer review Reviewed January 13, 2006 Featured article candidate Promoted January 24, 2007 Featured article review Demoted Current Status: Former featured article

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Archive 1 Archive 2

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Processor was merged into Central processing unit (this article). That history now exists at Talk:Central processing unit/Processor article history.--Commander Keane 07:36, 14 January 2006 (UTC)

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Contents 1 I Want to buy a PC 2 List of CPU flags? 3 Good article... 4 Peformance comparison of common processors 5 manufacturers of central processing units? 6 Different CPU models? 7 Link inappropriate? 8 Why??? 9 Moving some content from CPU Design? 10 CPU Operation

[edit] I Want to buy a PC

I'd like to buy a new PC but this article doesn't help me with regard to choosing an appropriate processor. I think that Wikipedia should have seperate pages for people such as me that doesn't go into lavish detail about everything.

What do others think ? —The preceding unsigned comment was added by 144.82.242.3 (talk) 19:53, 27 December 2006 (UTC).

Wikipedia isn't a compendium of HOWTOs or buyers' guides. The information you're after is better found on review and rating sites like Tom's Hardware and Anandtech. It definitely isn't encyclopedic and doesn't belong on Wikipedia proper (perhaps one of the sister WikiMedia projects like Wikibooks, though). -- mattb @ 2006-12-27T20:52Z

[edit] List of CPU flags?

Is there a list somewhere (in Wikipedia or not) of common CPU flags (like SSE, APIC, MMX, 3dnow...) and what they mean? (Other than the one I started building at User:Dcljr/Sandbox#List of CPU flags, of course.) - dcljr (talk) 17:31, 23 May 2006 (UTC)

Uhh... For what architecture? Try reading the programmer's manual for whatever ISA you're using (looks like late x86 to me). -- uberpenguin @ 2006-05-23 18:36Z

That list is a mixed bag of terms, some of which refer to features (such as MMX, SSE, 3DNow!), some of which refer to components (such as APIC and MTRR), some of which refer to I/O buses (such as MCA and VME), some of which refer to instructions (such as SYSCALL) - there's really nothing they all have in common other than being computer hardware terms (and some of them might not even be computer hardware terms - "DE" goes to a disambiguation page, and the only computer term there is "Desktop Environment"). Guy Harris 21:26, 23 May 2006 (UTC)

Yeah, it's a mixed bag exactly because I don't know what they all mean! <g> Anyway, most of these are from the "flags" entry of "cpuinfo" in Linux (see, for example, [1]). - dcljr (talk) 19:31, 24 May 2006 (UTC)

The ones from "cpuinfo" are probably the flags you get from the x86 CPUID instruction, listing the capabilities of the processor. Lists of them can be found in the Intel and AMD documentation of the x86/IA-32 (including EM64T) and AMD64 instruction sets; see, for example, the description of the CPUID instruction in IA-32 Intel® Architecture Software Developer’s Manual Volume 2A: Instruction Set Reference, A-M. "MCA" and "VME", unfortunately, are ambiguous; they can refer to the MCA and VME buses, which are system I/O buses and are characteristics of the system as a whole rather than of the processor, or they could refer to "Machine Check Architecture" and "Virtual 8086 Mode Enhancements", which are x86 CPU features and have nothing to do with the MCA or VME buses - the x86 CPU features are the ones reported by "cpuinfo". Guy Harris 19:35, 24 May 2006 (UTC)

Aha! I just found List of computing and IT abbreviations, which would seem to be the place for this info, but the few terms I've looked for so far haven't been in the list. - dcljr (talk) 06:18, 25 May 2006 (UTC)

Actually, I think CPUID would be an even better place for this information (please add any details it leaves out). --70.189.77.59 17:54, 27 October 2006 (UTC)

[edit] Good article...

Sorry for cluttering the talk page, I just want to say this is a really well-written and informitive article. 128.208.41.109 05:25, 25 May 2006 (UTC)

[edit] Peformance comparison of common processors

It would be useful to read a comparison of the performances of common processors (either in a table in the article, or an external link).

I don't care for the idea. Performance comparisons are very involved and detailed discussions, are often quite subjective and subject to testing bias, and would bulk up the article significantly. Furthermore, a fair sample of performance comparisons from the entire history of CPUs could be very difficult to contain in a table. That being said, I think it might be an interesting and relevant factoid to include a short sample comparison of, say, the integer performance of a very early von Neumann computer to a modern microprocessor. If you want to collect some figures on modern microprocessors, I can look up the data for old computers. -- mattb @ 2006-09-14T04:41Z

I think there is room for such a table *somewhere* in Wikipedia, but I agree central processing unit is not the place. Please stick that information in benchmark (computing) until we find a better place? --70.189.77.59 17:54, 27 October 2006 (UTC)

Check out iCOMP and PR rating. BebopBob 01:56, 21 December 2006 (UTC)

[edit] manufacturers of central processing units?

Who are the main manufacturers of CPUs and how is performance measured

1. Too many to briefly enumerate. 2. In too many ways to briefly enumerate. Reading CPU design may provide a little enlightenment. -- mattb @ 2006-10-22T02:16Z

I like the CPU design article. It mentions As of 2004, only four companies are actively designing and fabricating state of the art general purpose computing CPU chips. So -- are 4 too many to enumerate? Or do we need to update that article to include those other companies you are thinking about?

Those are excellent questions. Please help us improve Wikipedia to make the answers better and to make the answers easier to find. Many companies that design CPUs are Fabless semiconductor company, who pass their design over to some other Semiconductor companies, which actally fabricate the CPU. CPU performance is measured using benchmarks -- but be aware that there is no one "performance" number -- one CPU may perform one benchmark faster, but some other CPU may perform your actual application faster. Do we need to mention/link to these things in the article? --70.189.77.59 17:54, 27 October 2006 (UTC)

[edit] Different CPU models?

What is physically different between similar processors, eg. one that is 2 ghz, and one that is 3 ghz?

There may be absolutely nothing physically different about them, or they may be totally different. You'd need more information than just clock speed to say. -- mattb @ 2006-10-19T19:03Z

Say they were the exact same model, and only the clock speed is different? Would only the multipilier be changed in the hardware?

Well, in some form or another the global clock signal will have its period decreased. Whether that means changing a clock multiplier or the target frequency of some oscillator is application-specific. -- mattb @ 2006-10-22T02:13Z

Certainly one *can* run a 3 GHz processor at 2 GHz, so there is not necessarily a physical difference.

However, most 2 GHz processors cannot run at 3 GHz -- there *is* a physical difference.

So, from least amount of difference to most difference, we have:

• only the external clock speed is different -- no internal difference.
• only the internal multipler is different.
• They were manufactured the same way, with the same photomask, but chip-to-chip and wafer-to-wafer variations in blurriness and defects made some chips fail to run at the designed speed ("weak transistors"), but the chips passed the test at a slower speed.
• They were manufactured according to the same layout, but a photomask shrink produced smaller, faster transistors and shorter, faster wires.
• The layout was tweaked slightly ("transistor sizing", "strengthening transistors") to improve the critical path.
• the chip was completely re-designed (deeper pipelines, improved clocking tree, smaller cache, etc.) to shorten the critical path.

Does that answer your question?

(Should I move this to the CPU design article?) --70.189.77.59 17:54, 27 October 2006 (UTC)

[edit] Link inappropriate?

The external link to cpu-collection.de, a documentary website about the history of microprocessors, has been removed for being "inappropriate". In an article about Central Processing Unit - isn't this link helpful and therefor appropriate? What do you think? —The preceding unsigned comment was added by Morkork (talk • contribs) .

It was removed partially because you were adding it to several articles without first discussing its inclusion. That is generally viewed as WP:SPAM, especially if you have something to do with the website you are adding. I'd say that link may be appropriate for microprocessor (ask on the talk page), but not this article. -- mattb @ 2006-11-08T01:25Z

[edit] Why???

Why does this get vandalized so much, anyway??? What makes this a popular target??? 170.215.83.212 07:44, 17 November 2006 (UTC)

You got me... I guess it's just people trying to mess up a good thing. -- mattb @ 2006-11-17T16:07Z

[edit] Moving some content from CPU Design?

I created a new section called Markets in the CPU design article. I think that section probably belongs here. What do people think?

Even more important, the CPU Design article has a list of micro-architectural concepts, similar but not exactly the same as the Design and Implementation section of this article. This article doesn't mention RISC nor cache, for example. All of these ought to collected in one place. I don't have an opinion on where this micro-architectural stuff goes - either here or CPU design. Opinions?

Previously, it was discussed that the CPU design article should concentrate on the actual implementation task of designing a CPU. I agree with that. Things like micro-architecture and markets straddle the line between architecture and implementation so its difficult to figure out where this content belongs. Dyl 17:03, 18 February 2007 (UTC)

I think the content you added should rightly stay in the CPU design article. This is an overview article and it is far more appropriate for it to describe the operation of CPUs at a high level rather than muck around with a lot (and there is a LOT to be said) of detail. This article actually does mention caches, but it defers to the article on cache rather than taking a lot of space to explain it here. -- mattb @ 2007-02-19T14:44Z

Ah, I see the overview aspect now. Previously, I did not see it as an overview as it is poorly titled. The titles of the sections mention the names ILP and TLP but don't explicitly state what they are, instead they name specific sub-topics. I'm renaming the sections to show they are different types of parallelism. I believe that's the aspect the overview is discussing. --Dyl 08:40, 20 February 2007 (UTC)

That's fine, but the new names you've given to the headings are a bit longer than preferable. Could we shorten them a bit? How about just "Instruction level parallelism", "Thread level parallelism", and "Data parallelism". -- mattb @ 2007-02-20T15:11Z

[edit] CPU Operation

I dono what happened to the CPU Operation section, but it's filled with example pictures and crap text now. 24.7.201.100 19:56, 18 February 2007 (UTC)

That was probably vandalism you saw that has since been removed. -- mattb @ 2007-02-19T14:45Z