PCI-Express Compliance: Does It Even Matter?

For a while now we’ve been under the impression that video card size and power consumption was ultimately capped by the PCI-Express specification. At present time the specification and its addendums specify normal (75W), 150W, 225W, and 300W PCIe card operation. In the case of 300W cards in particular this is achieved through 75W from the PCIe slot, 75W from a 6pin PCIe power connector, and 150W from an 8pin PCIe power connector. As the name implies, the PCIe specification also defines what the 6pin and 8pin power connectors are supposed to be capable of, which is where 75W and 150W come from respectively.

Altogether the biggest, most powerful card configuration in the PCIe specification allows for a 12.283” long, triple-wide card that consumes 300W. To date we’ve never seen a card exceed the physical specifications, but we’ve seen several cards exceed the electrical specifications. This includes cards such as the 5970 and some overclocking-oriented 5870s that were designed to handle more than 300W when overclocked, and even more exotic cards such as the Asus ARES 5870X2 that simply drew more than 300W from the get-go. We have yet to see a reference design from AMD/NVIDIA however that exceeds any part of the PCIe specification by default.

So it has been clear for some time now that cards can exceed the PCIe specifications without incurring the immediately wrath of an army of lawyers, but at the same time this doesn’t establish what the benefits or losses are of being or not being PCIe compliant. To have a reference design exceed the PCIe specifications is certainly a new mark for the GPU industry, so we decided to get right to the bottom of the matter and get an answer to the following question: does PCI-Express compliance matter?

To answer this question we went to two parties. The first of which was of course AMD, whose product is in question. AMD’s answer basically amounts to a polite deflection: it’s an ultra-enthusiast card that at default settings does not exceed the power available by the combination of the PCIe slot and PCIe power connectors. Furthermore, as they correctly note, the 6990 is not the first card to ship at over 300W, as the ARES and other cards were drawing more than 300W a year ago. It’s a polite answer that glosses over the fact that no, the 6990 isn’t technically PCIe compliant.

To get a second opinion on the matter we went straight to the source: The Peripheral Component Interconnect Special Interest Group (PCI-SIG), which is the industry group that defines the PCIe standard and runs the workshops that test for product compliance. The PCI-SIG’s member list is virtually everyone in the computing industry, including AMD, NVIDIA, and Intel, so everyone has some level of representation with the group.

So what does the PCI-SIG think about cards such as the 6990 which exceed the PCIe specification? In a nutshell, they don’t directly care. The group’s working philosophy is closer to approving cards that work than it is about strictly enforcing standards, so their direct interest in the matter is limited. The holy grail of the PCI-SIG is the PCI Express Integrators List, which lists all the motherboards and add-on cards that have passed compliance testing. The principal purpose of the list is to help OEMs and system integrators choose hardware, relying on the list and by extension PCI-SIG testing to confirm that the product meets the PCIe standards, so that they can be sure it will work in their systems.

The Integrators List is more or less exclusively OEM focused, which means it has little significance for niche products such as the 6990 which is split between end-user installation and highly customized OEM builds. The 6990 does not need to be on the list to be sold to its target market. Similarly the 5970 was never submitted/approved for listing, and we wouldn’t expect the 6990 to be submitted either.

It is worth noting however that while the PCI-SIG does have power specifications, they’re not a principal concern of the group and they want to avoid doing anything that would limit product innovation. While the 300W specification was laid out under the belief that a further specification would not be necessary, the PCI-SIG does not even test for power specification compliance under their current compliance testing procedures.  Conceivably the 6990 could be submitted and could pass the test, leading to it being labeled PCIe compliant. Of course it’s equally conceivable that the PCI-SIG could start doing power compliance testing if it became an issue…

At the end of the day as the PCI-SIG is a pro-compliance organization as opposed to being a standard-enforcement organization, there’s little to lose for AMD or their partners by not being compliant with the PCIe power specifications. By not having passed compliance testing the only “penalty” for AMD is that they cannot claim the 6990 is PCIe compliant; funny enough they can even use the PCIe logo (we’ve already seen a Sapphire 6990 box with it). So does PCIe compliance matter? For mainstream products PCIe compliance matters for the purposes of getting OEM sales; for everything else including niche products like the 6990, PCIe compliance does not matter.

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  • james.jwb - Tuesday, March 08, 2011 - link

    I doubt it. That would be 80 dBA at ear level compared to whatever Ryan used. At ear level it's going to be a lot lower than 80.

    Still, that doesn't take away the fact that this card is insane...
    Reply
  • Belard - Tuesday, March 08, 2011 - link

    The card needs 3 slots to keep cool and such. They should have made a 2.5-slotted card, but with a bit of a twist.

    Channel the AIR from the front GPU chamber into a U-duct, then split into a Y that goes around the fan (which can still be made bigger. The ducts then exhaust out the back in a "3rd slot". Or a duct runs along the top of the card (out of spec a bit) to allow the fan more air space. It would add about $5 for more plastic.

    Rather than blowing HOT air INTO the case (which would then recycle BACK into the card!
    OR - blowing HOT air out the front and onto your foot or arm.

    Noise is a deal killer for many people nowadays.
    Reply
  • strikeback03 - Tuesday, March 08, 2011 - link

    That ductwork would substantially reduce the airflow, making a sharp turn like that would be a large bottleneck. Reply
  • burner1980 - Tuesday, March 08, 2011 - link

    I´m always wondering why reviews always neglect this topic. Can this card run 3 monitors @ 1920x1080p 120 HZ. 120 HZ monitors/beamer offer not only 3D but foremost smooth transitions and less screen tearing. Since this technique is available and getting more and more friends, I really would like to see it tested.
    Can anybody enlighten me ? (I know that Dual link is necessary for every display and that AMD had problems with 120 HZ+eyefinity) Did they improve?
    Reply
  • silverblue - Tuesday, March 08, 2011 - link

    ...with two slightly downclocked 6950s. Alternatively, a 6890, albeit with the old VLIW5 shader setup. As we've seen, the 5970 can win a test or two thanks to this even with a substantial clock speed disparity.

    The 6990 is stunning but I couldn't ever imagine the effort required to set up a machine capable of adequately running one... and don't get me started on two.
    Reply
  • Figaro56 - Tuesday, March 08, 2011 - link

    I'd love to see Jessica Alba's beaver, but that aint going to happen either. Reply
  • qwertymac93 - Tuesday, March 08, 2011 - link

    AUSUM SWITCH

    http://img202.imageshack.us/img202/8717/ausum.png
    Reply
  • KaelynTheDove - Tuesday, March 08, 2011 - link

    Could someone please confirm if this card supports 30-bit colour?

    Previously, only AMD's professional cards supported 30-bit colour, with the exception of the 5970. I will buy either the 6990 or Nvidia's Quadro based on this single feature.

    (Because somebody will inevitably say that I don't need or want 30-bit colour, I have a completely hardware-calibrated workflow with a 30" display with 110% AdobeRGB, 30-bit IPS panel and the required DisplayPort cables. Using 24-bit colour with my 5870 CF I suffer from _very_ nasty posterisation when working with high-gamut photographs. Yes, my cameras have a colour space far above sRGB. Yes, my printers have it too.)
    Reply
  • Gainward - Tuesday, March 08, 2011 - link

    Just a heads up for anyone buying the card and wanting to remove the stock cooler.... There is a small screw on the back that is covered by two stickers with (its under the two stickers that look like a barcode). Well removing that you will then notice a void logo underneath it... I just wanted to point it out to you all...

    Didnt bother us too much here seen as ours is sample but I know to some droppin £550ish UK is quite a bit of cash and if all you are doing is having an inquisitive look it seems a shame to void your warranty :-S
    Reply
  • mmsmsy - Tuesday, March 08, 2011 - link

    I'd like to know how do you benchmark those cards in Civ V. I suppose it's the in-game benchmark, isn't it? Well, I read some tests on one site using their own test recorded after some time spent in the game using FRAPS and I'm wondering if using the in-game test is that really different scenario. According to the source, in the real world situation nVidia cards' performance show no improvement whatsoever over AMD's offerings. If you could investigate that matter it would be great. Reply

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