Talk:PCI Express/Archive 2006

pic request

It would be nice if the article had photos of some pci-x devices, i.e. are the connectors similar to PCI?

There are plenty of pictures in the documents at pcisig.com. You could perhaps pick something out and ask their permission to include them if you really want one, but I'm going on to write an article on dielectric loss budgets. Dennis 21:31, 14 Jan 2005 (UTC)

I think this user meant photos of PCIe devices. The connectors are visually simillar and phyiscally incompatible. --Cmiyc 01:36, 3 August 2006 (UTC)

Non Tech Question

Much goodie techie stuff here, but what about putting a PCI-e card in a PCI slot, does that work ? regards a Non techie geek

As stated later on, PCIe and PCI/PCI-X are not mechanically compatible. Their physical layers (electrically) are completely different.--Cmiyc 01:36, 3 August 2006 (UTC)

Hot pluggability?

On pinouts.ru, the PCI Express pinout has some hot-plug detect pins. Is PCI Express hot-pluggable? And if it is, why? Mrdelayer~ 10:20, 15 July 2005 (UTC)

I believe they were planning on making a cable specification. Something like USB, but better.the1physicist 15:56, 15 July 2005 (UTC)

For servers and other high-up time systems. --Cmiyc 01:36, 3 August 2006 (UTC)

Card/slot combinations

What card/slot size combinations are possible? For example, can an x4 card be plugged into an x16 slot? Can an x8 card be plugged into an x4 slot?

I believe that with PCI, a 32-bit card could be plugged into a 64-bit slot, and a 64-bit card could (at least in some cases) be plugged into a 32-bit slot (it would just operate at the lower bandwidth). What are the comparable possibilities for PCI Express?

I hoped to find an answer to this question here, so presumably others may also.

--Beric 14:38, 26 July 2005 (UTC)

You can't overhang the cards like you can with PCI, but you can install lower speed cards into faster slots (and the rest of the pins are [of course] unused). So, you could put a x1 or x4 into your x16 slot if you wanted.

-Dan November 14, 2005

i was looking for this info, too. it appears you can, based on a 2004 test by Tom's (see link i added at bottom of link section (altho it may be a special/nonavailible BIOS). also, an ASRock Core 2 mobo either has just a x4 slot or a x16 slot that only runs at x4. i was curious to see if it was even worth considering it and that's the info my first 30 seconds of websearching turned up. looks to be "acceptable" at least up to a 6800 Ultra. not sure about higher... Plonk420 21:04, 17 August 2006 (UTC)

Performance Difference

Is there really noticible (higher than 5%) performance difference between PCI-e and AGP graphics card? I have used both versions of 6600GT and I cannot notice any difference even though the bridging chip should slightly slow it down. --Antilived 11:01, 6 August 2005 (UTC)

For the most part, there is little to no performance penalty for AGP. I do believe that a PCI-E 8X will be about 2% slower than 16X, and a 4X about 5% slower than a 16X.the1physicist 22:11, 6 August 2005 (UTC)

This is application-dependant. PCIex does have much less latency and overhead for small transactions. On an application doing lots of small texture updates (google for "uberflow" to have an example) the PCIex machine ended up being 80% faster than the AGP one on similar hardware! 83.176.117.138 08:03, 31 July 2006 (UTC)

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[[User:|User:]] 14:38, 28 October 2005 (UTC)

Looking at the Specfications for the TYAN Tomcat i7230A, it claims to have 2 PCIe x16 slots. One with x8 Signal and one with x4 signal. What does this mean?

There's three different speeds - card, slot, and signal. As long as the card is <= the slot speed, it will work. However, all of the slots could have less signal lines so they're really slower than expected. However, I don't know exactly where the difference is (perhaps in the bridge chip??). -Dan November 14, 2005

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PCI-X is merged with the PCI article. Suggest that this be merged with the PCI article, too? --BleachInjected 02:56, 4 November 2005 (UTC)

• I'd* have to say no, because unlike PCI-X (which was an extension of PCI), this is different physically. It's serial and has dedicated channels. It's designed to be compatable with PCI programming (only requiring a new transport), but it's not electrically similar.

-Dan November 14, 2005

HowStuffWorks article

I've read on howstuffworks in article about PCI next:

“ PCI-Express slots will also accept older PCI cards, which will help them become popular more quickly than they would if everyone's PCI components were suddenly useless. ”

How can it be true? Or may be that article too old? PCIe slots are completely different from PCI - or I'm mistaking? If my motherboard have both PCI & PCIe stots - is it mean that all PCI slots - are PCIe slots but with PCI-formfactor ? Or motherboard have 2 different buses PCI & PCIe ? And PCI slots will be works as usual with bus multiplexing ? —Preceding unsigned comment added by 81.200.2.184 (talk • contribs)

That information is just wrong. The slots are different, and the electrical interface is *very* different. Many (most?) motherboards with PCIe slots also have legacy PCI slots as well. It's also possible the author of that information was confusing PCIe with PCI-X.

Imroy 09:51, 30 March 2006 (UTC)

PEG ≡ PCI Express

Is PEG (PCI-Express For Graphics) 100% identical with normal PCIe or not? --Hhielscher 01:05, 16 April 2006 (UTC)

PEG == PCI Express Graphics. It is 100% identical, but is specifically called PEG because the slots sit directly off of the northbridge/MCH, so they have less latency for memory and CPU cycles. The regular PCI Express slots sit off the southbridge, and there's extra latency in communicating upstream to the northbridge. Rmcii 20:09, 13 May 2006 (UTC)

Outlook

The article says "As of 2006, PCI Express appears to be well on its way to becoming the new backplane standard in personal computers." However, since each PCI Express lane stands alone (as contrasted to the shared 32 or 64bit bidirection pins of regular PCI), it doesn't appear to match the definition of backplane given. I suggest that this be revised to "As of 2006, PCI Express appears to be well on its way to becoming the new internal expansion standard in personal computers." JDBoyd 13:49, 09 Aug 2006 (EST)

The article says that as of 2005 it looks like PCI-E may become the standard for PC's. Well it's half past 2006 and I think PCI-E has indeed become the standard for PC's. Anyone agree? Dionyseus 21:49, 14 July 2006 (UTC)

Its certainly dominated all other newcomers (PCI-X agp etc) but afaict its still got some way to go to kill off PCI as the dominiant general purpose expansion slot system. Plugwash 02:25, 26 August 2006 (UTC)

BW/clock

Where is the bandwidth and clock info? I believe this should be pointed out somewhere. 83.176.117.138 08:05, 31 July 2006 (UTC)

This question doesn't really make sense to me. What clock info? The bit rate is 2.5Gbit/s. The reference clock is 100MHz. There are sources on the actual bandwidth, after you account for some of the overhead and 8b/10b encoding.

I suppose his/her question is this (and it's also the same question I have): how does the reference clock affect the bandwidth, if at all? There's no info anywhere on this that I can see, and I think it would be highly valuable to people who want to know how overclocking the PCI-E clock affects overall speed, etc... The documentation for CPUs, AGP cards, and so on is so obvious, but I can't find the data anywhere for PCI Express cards. Does anyone here know the answer?

An issue that could be added: Operating System Support

My research shows that older Window OS's -- 95, 98, Me, NT4 -- won't run on systems with PCI Express. And Win2K may have problems.—Preceding unsigned comment added by 75.6.242.35 (talk • contribs)

Where have you run into this? Do you mean drivers like video cards? One of the advantages of PCIe is that the hardware and BIOS can "hide" the implementation so that the software just sees PCI like it has since the 90s. — RevRagnarok ^{Talk Contrib} 11:06, 6 September 2006 (UTC)

Most newer chipsets which support PCIe do not have drivers or any manufacturer support for older OSes including 98, NT, or ME. —Preceding unsigned comment added by 166.68.134.174 (talk • contribs)

Amount of lanes?

Is there any limit on how many lines a motherboard board can have? I saw a motherboard that has 3 PCIe 16x slots, 3x16 is 48 lanes total. -- Frap 07:58, 8 December 2006 (UTC)

The number of lanes on a motherboard is implementation-specific. They're only limited by the number of pins that can be crammed onto a chip package (another good reason to go serial), and by the ability to connect multiple chips together. There are large enterprise-level machines with many individual PCI buses (yes, buses, not slots) - I believe one use is to stuff them full of SCSI cards to access truly huge RAID arrays or tape archive units with many drives being fed my robotic tape handlers. Exactly the same thing could be done with PCIe. The only issue is how to connect so many buses and processors together. These large machines are very much like supercomputers with high-speed interconnects tying everything together. Anyway no, there is almost no limit on the number of lanes on a motherboard. --Imroy 09:20, 8 December 2006 (UTC)

article language

This is by no means a criticism of the PCIe specification -- merely a reminder that PCIe is not exempt to the rules of a layered packet protocol, no more so than other comparable high-speed serial technologies (such as Serial ATA and Fibre Channel). It seems to me this language doesn't belong in an encyclopedia article. How about (This is not an issue peculiar to the PCI express interface.) If nobody complains, I'll change it. Feel free to revert (with discussion).—Preceding unsigned comment added by 71.245.211.95 (talk • contribs) 05:56, January 17, 2006 (UTC)