Talk:Peripheral Component Interconnect

Comments on PCI protocol sections recently added to article

This is a discussion area for beating the above sections into shape for inclusion in the article. NOTE that as concerns here are addressed, the text above will change and so the comments might be out of date. (The inclusion has since happened; the sections have been moved into the main article.)

Comments by User:JMiall (talk)

• This was a solicited review of the section.
  • Interleaved responses by User:71.41.210.146 (talk)

(please post these to the talkpage there if you wish):

• You asked first of all if it read well to someone unfamiliar with the specs. I think that basically it does.
• I'm a bit worried though that there is too much detail, I'm not sure where is a good place to draw the line though. Possibly all this information should be split off to (an)other article(s) and summarised within this one?
  • Perhaps. Creating new articles is a pain for me, so maybe I'll leave that to someone else.
• I've not looked at everything you have put on the talkpage yet, I'll come back with some more comments if you found these useful.

Specific questions/issues to be going on with:

• Why is "asserted" in quotes?
  • That was for emphasis, because that was where asserted was defined. Should be italics, thanks.
• 'controlled by 5 main control signals' etc - is signal the right word here? ie are FRAME# etc the name of a particular line or the signals that are present on that line?
  • Yes, they are physical wires. You can see them in Conventional PCI#Connector pinout. (E.g. FRAME# is 34A.) Er... what is the distinction between "line" and "signal" you're making here? Generally, I think of them as synonymous, except that "signal" emphasizes information-carrying capacity. "+5V supply line", but "clock signal". I suppose that "signal" is more abstract, and e.g. two signals could be multiplexed onto the same wire...
• Also the when the lines/signals are mentioned they sometimes are put in brackets, sometimes commas and sometimes nothing.
  • I don't understand this one. [brackets]? Or (parentheses)? Can you give me an example?
• 'will remain high' - add 'voltage', also voltage needs linking in the main article
  • H'm... probably.
• 'each bus line be undriven' - given the potential for confusion for someone not too familiar with English is it possible to reword?
  • Okay. I tried to clarify.
• Link Pull-up resistor
  • Good point. Sorry.
• 'Signals nominally change on the falling edge of the clock' - should this be 'nominally' or 'normally'? Is the spec not specific about precisely when they should change?
  • Nominally, and no the spec is not. To be precise, they must change within a specific time window relative to the leading edge of the clock, so the signal has time to arrive at the receiver. This window is close to the falling edge of the clock, and I felt that the details of setup and hold times and clock jitter was definitely something that didn't below in Wikipedia; see the spec if you care about that level of detail.
• The wording rather implies at that all the PCI devices are concious intelligent beings. It is probably worth toning this down a bit. ie 'decides', 'promise', 'generally attempt', 'desire'
  • H'm... this is because the actual function of the PCI device is not relevant here and the reason why it "wants to talk" to the PCI bus is not discussed. The language sort of follows naturally from that. I can try a bit, e.g. promise can be changed to "guarantee," but does anything particularly grate?
• '(There are rules for how it is supposed to behave, but they will be mysterious to any single device.)' - is this necessary?
  • In the middle of emphasizing that the GNT# signal might go away at any time for no obvious reason, it occurred to me that that isn't the same as no reason at all.
• link 'bus master'?
• 'but may not start one unless it observes GNT# asserted the cycle before it begins a transaction' - unclear 'it's
• 'so there are actually three signals' - fairly colloqial language
• 'Actually, it has 2.5 cycles' - 'they' not 'it'?
  • Perhaps "each target".
• 'On the fifth cycle...' - I'm unsure what this paragraph means.
  • Okay, I'll work on it. See the figure below with numbered
• 'Access to PCI configuration space is a special case' - of what?
  • Of address decoding; many address bits are ignored, and IDSEL matters. Thanks, I'll tweak it.
• 'enables' - link or explain?
  • Don't the following sentences do it adequately?
• 'In case of a write' - missing 'the'
• 'more purely'?
  • Arrgh.
• Several times you use 'read' or 'write' when it would probably be clearer to use 'read signal' or something similar
  • I can't find an example. Can you point one out?
• 'line turns around during' - what does turns around mean here?
  • This is the undriven cycle discussed above. I expanded that section, because it becomes important later.

Main article:

• 'However, they are not wired in parallel as are the other traces' - this needs explaining. Traces have not been mentioned yet and it is unclear what this means any way due to the 'are not...as are...'
  • Thanks, will fix.

JMiall₰ 23:16, 2 August 2009 (UTC)

• 71.41.210.146 (talk) 01:44, 3 August 2009 (UTC)

Conventional PCI vs. PCI Local Bus

The lead says "Conventional PCI (part of the PCI Local Bus standard...)". My questions are:

• Is Conventional PCI an industry term or just something made up by Wikipedians to distinguish the original PCI from newer versions (PC-X, PCIe).
• If Conventional PCI is part of the PCI Local Bus standard, what else is in that standard? --Kvng (talk) 21:47, 1 September 2010 (UTC)

PCI-SIG uses the terminology Conventional PCI (e.g. [1]). I assume PCI Express would be another part of the PCI Local Bus standard. —Ruud 13:04, 15 February 2011 (UTC)

OFFICE action

The following were removed as a result of a DMCA takedown notice, per the office action policy. Please do not readd these. The article remains open for editing, with the exception of any links to these specifications. If you'd like to appeal, please email your notice to me at philippewikimedia.org.

PCI Local Bus Specification, Revision 2.1

PCI Local Bus Specification, Revision 2.2

PCI Local Bus Specification, Revision 3.0

Office actions may not be reversed except through the Wikimedia Foundation office. The pertinent policy lives at WP:OFFICE. Philippe Beaudette, Wikimedia Foundation (talk) 01:42, 4 January 2011 (UTC)

This is quite pointless because you can still see it in the article history. --Hinata talk 15:46, 21 January 2011 (UTC)

Seconding the previous' posters finding. Also, are you <censored by myself>? The original Document is still online, publicly available and a top hit on google. I bet this DMCA Notice was automatically generated. Furthermore, completely removing the reference is just stupid - wouldn't it suffice to just remove the link? Effin' lawyers.. --Roeme (talk) 11:12, 23 January 2011 (UTC)

If it's not a valid DMCA compliant wouldn't it be possible to file a DMCA counter notice? --nn123645 (talk) 01:30, 2 February 2011 (UTC)

Since PCIe is quickly replacing Conventional PCI, and PCI-SIG should release the Conventional PCI spec for a reasonable price to non-members. • Sbmeirow • Talk • 15:15, 23 January 2011 (UTC)

For those who are interested, I've posted the DMCA take-down notice at this location on the Foundation's wiki. It specifically mentions the reference section and requires that we remove the specifications. At this point, until or unless we receive a DMCA counter-notice, those standards can not be reposted. If we were to allow that to happen, we threaten the immunity under which we operate through the Safe Harbor provisions of the Digital Millenium Copyright Act. I'd be happy to provide someone with instructions regarding where to send a counter-notice if someone has a valid couter-claim, but be aware that it would be a statement under penalty of perjury that you have a valid copyright counter-claim. Philippe Beaudette, Wikimedia Foundation (talk) 01:24, 24 January 2011 (UTC)

Don't you see that the one writing this notice didn't understand that it's not wikipedia that's hosting that PDF?! From my understanding of this notice and the DMCA in general, it would be completely okay to CITE the specification - without linking to it. Someone readded the reference in the mean time (even with a link to the pci sig), so further discussion is moot. Next time, I'd recommend just to break/remove the link. Removing the ref alltogether in my opionion is just excessive and feels like censorship. --Roeme (talk) 10:07, 24 January 2011 (UTC)

I will execute a DMCA take-down exactly as instructed by legal. Anything else compromises our position. Your understanding may or may not be correct, but I will not follow your interpretation - I am duty bound to follow the interpretation of our legal team. Philippe Beaudette, Wikimedia Foundation (talk) 02:08, 25 January 2011 (UTC)

Roeme, see Wikipedia:OFFICE#DMCA_compliance, particularly "the Foundation is required to comply with validly formulated notices even if they are spurious". I'm not saying this one is spurious. The point is that the Foundation complies to keep its safe-harbor status, not because it has independently assessed the merits of the claim (although they may do that anyway).--Chaser (talk) 01:57, 1 February 2011 (UTC)

Well this kinda depends. It can be argued that linking to copyrighted material in this way is not a copyright violation, and thus usage of DMCA for this purpose (getting a website to remove a link) is abuse of the DMCA system. The question of linking to copyrighted material is FAR from settled. While what the foundation is doing, is acting on the safe side, it is (as with the caving in to another user who didn't understand copyright [alexander liptek]) a dangerious precedent that we should keep a close eye on. I don't want to arrive at a place where the foundation always acts on the safe side, and leaving this battles of DMCA abuse entirely to its editors. 93.111.234.204 (talk) 16:51, 1 February 2011 (UTC) (which would be User:TheDJ) 93.111.234.204 (talk) 16:52, 1 February 2011 (UTC)

I also think we should revisit wether we want these DMCA complaints marked in articles. A nice red meta template with "Specifications removed after DMCA complaint of copyright claimant" might be a useful addition to raise awareness -- TheDJ —Preceding unsigned comment added by 93.111.234.204 (talk) 16:55, 1 February 2011 (UTC)

Citations

Someone please file a DMCA counter notice with the Foundation. We need to be permitted to footnote the spec, without hotlinks. --Hroðulf (or Hrothulf) (Talk) 14:39, 3 February 2011 (UTC)

We can cite the spec in the same way that we cite a print source or a paywalled online source. --Damian Yerrick (talk | stalk) 15:32, 13 February 2011 (UTC)

"The article remains open for editing, with the exception of any links to these specifications." (emphasis mine) I interpret this as stating we can still reference the specs, as long as we don't add any hyperlinks to pirated copies. —Ruud 12:38, 15 February 2011 (UTC)

What makes no sense to me is that the notice cites only the standards, not hyperlinks thereto. The notice is "seeking the immediate removal of the Local Bus Specifications from the Infringing Entry" (emphasis added). The Specifications are defined quite precisely by the copyright registrations, and have never been part of any wikipedia entry. The notice does not mention links in any way, shape or form. Anyway, I'll replace them with Google "I'm Feeling Lucky" links. 71.41.210.146 (talk) 01:11, 7 March 2011 (UTC)

Please don't. Hyperlinking to infringing copies of the specs, whether directly or indirectly through Google's "I'm feeling lucky" link, is still assistance in copyright infringement. The DMCA notice did not explicitly mention the URL exactly because it wanted to be wide enough to cover your "trick" as well. —Ruud 16:28, 20 March 2011 (UTC)

Er, AFAICT, the original DMCA notice was not even wide enough to cover linking to the spec; I asked why Wikimedia legal made that extrapolation. (In my ignorance, I'm assuming it's, "they're pissed about something, so we'll assume they object to the status quo", but it also looked like a mass-mailed form letter, so maybe they didn't do careful review.) See the exact words I quoted (and I don't believe I took them out of context) from the notice above. They asked for removal of the specifications from the entry, and did not mention or even allude to pointers to the specifications or instructions how to find the specifications. (If they did, I'd wonder if we could not link to the PCI SIG's version!)

If Philippe or WMF legal thinks otherwise, they can say so. 71.41.210.146 (talk) 20:11, 20 March 2011 (UTC)

P.S. I have asked User talk:Philippe (WMF) for his input to arbitrate the point. —Preceding unsigned comment added by 71.41.210.146 (talk) 20:22, 20 March 2011 (UTC)

No, there is absolutely no question is this case that we're not allowed to link to unauthorized copies of documents copyrighted by the PCI-SIG. We shouldn't have been doing this in the first place, we certainly shouldn't be doing this after they sent an, in this case entirely reasonable, DMCA takedown notice. Now I don't know which part of Philippe's: "The article remains open for editing, with the exception of any links to these specifications" and "Under no circumstance are editors to remove this protection or edit in an attempt to circumvent the letter or spirit of it. Any attempts to provide such information will result in the reversion and suppression of the edits made, and the user in question may be blocked for an indeterminate length of time." you didn't understood the first time, but for your own good I'd suggest you try to read and understand them once more. —Ruud 21:06, 20 March 2011 (UTC)

So I included a link to a link to the document. ("All problems in computer science can be solved by another level of indirection.") I assume that Philippe is patrolling the page (there are exactly three office actions in progress, hardly a chore to keep track of), so I didn't notify him personally, but I announced it both in the edit summary and on the talk page here. Then when I disputed your opinion, I did notify him personally on his talk page. Because I might be wrong. I think this is reasonable evidence of good faith. (I am not trying to circumvent the spirit of the office action, but I am most assiduously trying to circumvent the spirit of Schwabe, Williamson, and Wyatt's "Take Down Notice Pursuant to 17 U.S.C. § 512(c)"; those who live by the letter may die thereby.) Have you actually read the DMCA notice itself? It lists specific documents. It does not list the PCI-to-PCI Bridge Architecture Specification, revision 1.1, so of course I happily included a link to that document. (I also included a link to the Revision 2.3 specification, which is not listed as part of the restrictions above, but was listed in the DMCA notice; this is perhaps questionable.) But the point is that it requested removal of the specifications. They're gone. They never were there. Despite the laywer's "reasonable belief that the Local Bus Specifications are being distributed and displayed as part of the Infringing Entry" (emphasis added), the entry never has included them.

There is mention in the DMCA about links. That's 17 U.S.C. § 512(d), not (c). It's definitely a hot topic of legislation (the DMCA does not establish liability for linking, only provides a safe harbor for whatever liability might exist), but in any case the letter, by specifying only (c), excludes (d). I think WMF legal's interpretation is already incorrectly overbroad, but I'm not going to argue that. I am going to go up to the line they've drawn. 71.41.210.146 (talk) 00:24, 21 March 2011 (UTC)

Now what ever flawed legal interpretation of this situation you happen to have is completely irrelevant. The WMF legal team has decided we should not link to any copy of these specifications. This obviously includes any other material infringing on PCI-SIG's, or anyone else's for that matter, copyright, not mentioned explicitly in the notice. Do not add such material to the article, this talk page, or anywhere else. I'm not going to warn you again. —Ruud 08:20, 21 March 2011 (UTC)

*Sigh*. I have not now, nor ever included any copyright-infringing material in a wikipedia article. I don't intend to.

Whether telling people where to find (i.e. linking to) copyright-infringing material is a form of copyright infringement is a hotly debated and unsettled point of law. Your statement "This obviously includes any other material infringing on PCI-SIG's, or anyone else's for that matter, copyright, not mentioned explicitly in the notice." is, IMHO, completely and utterly unwarranted. The notice, and subsequent office action, was narrow and specific. There's no need to generalize to suppressing all material that might annoy someone. If wikipedia removed everything that someone somewhere wished it didn't include, it would turn into Newegg product reviews.

Find me one word, in the lawyer letter, or any office action notice, or anywhere else on wikipedia, that suggests that anyone except you has any problem with including a link to the PCI bridge architecture specification. The Office Action notice is at the top of this section, if you want to re-read it. (Also, find me one word that suggests that adding the link anywhere except in the Conventional PCI article is problematic.) As I said, my interpretation disagrees with WMF legal's, but I'm not challenging that. I'm disagreeing with your interpretation, and I am willing to challenge that. Unless you have some authority to speak for WMF legal that I'm got aware of.

I've explicitly asked Philippe for a ruling. Can we just wait until we get one? 71.41.210.146 (talk) 14:59, 21 March 2011 (UTC)

Let me quote Philippe (again):

The article remains open for editing, with the exception of any links to these specifications.

(Emphasis mine). That shouldn't be too hard to comprehend, right? If you link to material infringing on someone's copyright one more time, you will be blocked. This is Wikipedia, not the Pirate Bay. —Ruud 15:36, 21 March 2011 (UTC)

And I read that, and obeyed that. To the letter. I included links to other specifications (not the listed ones), and links to google searches for the listed specifications. As I said, up to the line. I was very careful not to cross it. If WMF wants to tell me the line has moved, okay. But I don't see why your personal interpretation deserves more weight than mine. 71.41.210.146 (talk) 16:19, 21 March 2011 (UTC)

I'm lazy to read the whole case and it probably isn't necessary anyway but is there actually any doubt the link above is copyright infringing? If so, I don't think any of us give a damn whether we were specifically asked to take it down. Our policy is clear and has been since long before this case, we don't link to copyright violations. The fact that this time it required a DMCA notice before we removed it, after they already asked us nicely is rather scary but if my understanding of what's going on is correct, it doesn't change the fact we are majorly in the wrong here and should have removed it a long time ago before anyone even asked nicely. If it's claimed the work is not copyright infringing, can someone briefly explain why? Is it that the work is not copyrighted or that the place we are linking to has permission from the copyright holder to host it? Or is it something complex like the place hosting it is located in a country where it's not copyrighted but it is in the US? Nil Einne (talk) 18:03, 21 March 2011 (UTC)

Nil, thank you. I had never read that section. Or if I had, I forgot it. I'll have to study it in more detail. In particular, I'll have to read the discussion archives for limits on the threshold of "knowing". I have many times installed links to freely available versions of academic papers (e.g. on a preprint server or the author's own web site, as opposed to behind a journal paywall) or newspaper articles, in simple ignorance of the copyright status of the copies I'm linking to. I'll do a bit of reading. (14 pages of talk archives, here I come...) 71.41.210.146 (talk) 18:52, 21 March 2011 (UTC)

I think linking to an authors website for journal articles would generally be fine because journals often do allow authors to host the article themselves subject to some conditions so it's reasonable for us to presume these aren't copyvios. To be fair, I wouldn't say many authors actually know what they're doing (except perhaps for legal ones) so some of them are probably copyvios but particularly if they're on a university website there are people running them who do care about copyright and the journals themselves know that so it would usually still be fair for us to just presume there's no copyvios unless there is actually evidence something is a copyvio. In cases when it's not reasonable to presume the content we're linking to has the copyright holders permission (i.e. there's a reasonable chance it is a copyvio) we don't usually allow it. Youtube is the classic example when the content is apparently not uploaded by the copyright holder (nowadays the copyright issues is particularly for music is not always as clear cut but we usually still don't allow it) but it applies to basically anything. While there are potential legal issues relating to contributory infringement, I don't believe this is really the primary reason for our policy, it's more of wanting to respect copyright. Nil Einne (talk) 16:04, 31 March 2011 (UTC)

Maybe references can be simple "<ref>PCI Local Bus Specification revision 2.3 2002-03-29</ref>" instead of direct link with google?, any person can lookup these things anyway. The important point must be to point to what specification and what section that is referenced? Electron9 (talk) 04:20, 20 May 2011 (UTC)

New section: PCI bus latency

{{editsemiprotected}}

It's included verbatim below; sorry if this looks a bit messy on the talk page, but it seems easiest to cut & paste this way. It should go between "PCI bus transactions" and "PCI bus bridges" (the latter of which needs work). Thank you! 71.41.210.146 (talk) 21:33, 20 March 2011 (UTC)

Extended content

PCI bus latency Soon after promulgation of the PCI specification, it was discovered that lengthy transactions by some devices, due to slow acknowledgments, long data bursts, or some combination, could cause buffer underrun or overrun in other devices. Recommendations on the timing of individual phases in Revision 2.0 were made mandatory in revision 2.1: A target must be able to complete the initial data phase (assert TRDY# and/or STOP#) within 16 cycles of the start of a transaction. An initiator must complete each data phase (assert IRDY#) within 8 cycles. Additionally, as of revision 2,1, all initiators capable of bursting more than 2 data phases must implement a programmable latency timer. The timer starts counting clock cycles when a transaction starts (initiator asserts FRAME#). If the timer has expired and the arbiter has removed GNT#, then the initiator must terminate the transaction at the next legal opportunity. This is usually the next data phase, but Memory Write and Invalidate transactions must continue to the end of the cache line. Delayed transactions Devices unable to meet those timing restrictions must use a combination of posted writes (for memory writes) and delayed transactions (for other writes and all reads). In a delayed transaction, the target records the transaction (including the write data) internally and aborts (asserts STOP# rather than TRDY#) the first data phase. The initiator must retry the exact same transaction later. In the interim, the target internally performs the transaction, and waits for the retried transaction. When the retried transaction is seen, the buffered result is delivered. A device may be the target of other transactions while completing one delayed transaction; it must remember the transaction type, address, byte selects and (if a write) data value, and only complete the correct transaction. If the target has a limit on the number of delayed transactions that it can record internally (simple targets may impose a limit of 1), it will force those transactions to retry without recording them. They will be dealt with when the current delayed transaction is completed. If two initiators attempt the same transaction, a delayed transaction begun by one may have its result delivered to the other; this is harmless. A target abandons a delayed transaction when a retry succeeds in delivering the buffered result, the bus is reset, or when 215=32768 clock cycles (approximately 1 ms) elapse without seeing a retry. The latter should never happen in normal operation, but it prevents a deadlock of the whole bus if one initiator is reset or malfunctions.

 Done Stickee (talk) 11:10, 21 March 2011 (UTC)

Suggestion to make article more practical

I'm posting this suggestion with the hope that someone skilled in wikipedia editting might agree and add this to the article. I attempted to install a PCI to USB adapter card (a common piece of computer hardware) to an old computer motherboard in order to increase the number of USB slots (a very common thing to do). I assumed PCI cards are "one size fits all" but found out that the card that I was attempting to install did not fit. I then discovered that there are two standards of PCI (3.3 V and 5 V). One is new, the other old, and each is physically "keyed" so that you cannot insert a 3.3V card into a 5 V slot, and vice versa, unless the card is keyed for both. The solution for me was to purchase a card that was keyed for my older motherboard.

This article is what gave me this knowledge, but it was difficult to figure out. Yet, I am certain my situation is very common, and may be one of the primary reasons why a person would be seeking to read about the technical characteristics of PCI.

To accomodate these imagined "other people", I think this article could be improved by creating a special section describing the situation I experienced, with the intent to quickly helping people similarly situated understand their problem and find their solution.

Jonny Quick (talk)Jonny Quick —Preceding undated comment added 15:04, 22 May 2011 (UTC).

Unfortunately, Wikipedia is not an instruction manual. --Redrose64 (talk) 14:06, 23 May 2011 (UTC)

Censorship

Someone file a counter-notice already! This censorship has gone on long enough! --134.10.114.238 (talk) 01:23, 17 July 2011 (UTC)