Benchmarking AMD's 768-Shader Pitcairn: Not For Public Consumption

Last week we reported that an engineering sample card with 768 shaders accidentally found its way into our lab instead of the HD 7850 we were expecting. This GPU may be meant for engineers, but it piqued our interest, since it happens to fill a large gap.

In last week’s news story AMD Pitcairn With 768 Shaders: What is This Mystery Chip?, we reported that, while testing a pre-production sample Radeon HD 7850 shipped to us in a rare single-slot form factor, we discovered a mysterious GPU that didn't match the Pitcairn we were expecting. Instead of coming equipped with the usual 1024 shaders, our engineering sample sported only 768 active shader cores.

We made a number of phone calls and exchanged a number of emails with AMD in an attempt to clarify our sample's origin and intention. What we found was that the 768-shader part did not, in fact, represent a piece of silicon destined to drive an upcoming super-secret derivative product. Rather, the GPU was only intended for board partners. It was never meant to go on sale, and it was certainly never supposed to land in our lab.

But if the part wasn't intended to sell or test, what was its purpose? There is a good explanation for its existence. For AMD’s add-in board partners, it is important to get their hands on GPUs as early as possible. Early access allows them to build boards in preparation for a launch. On the other hand, AMD is wary of leaks that would give away the performance profile of its GPUs in a very competitive graphics market. That’s where deliberately-hobbled engineering samples like this one come into play, allowing board partners to start developing their custom implementations with a chip that thermally and electrically simulates the final product. Meanwhile, AMD doesn’t need to worry about the performance attributes of its final effort getting outed by a company with unfettered access to its technology.

There remain a few points for us to clarify, though. When the single-slot Radeon HD 7850 that we tested appears for sale, we're told that it will feature a complete 1024-shader Pitcairn GPU. Obviously, the sample we're testing today isn't indicative of that final production product. To that end, the benchmark results we'll be presenting on the following pages are most easily thought of as experimental. We have a card here that nobody else has. It's properly recognized by AMD's Catalyst driver as a Radeon HD 7800-series board. And it effectively operates as a single-slot piece of hardware. AMD stresses that, at least for now, there are no plans to produce a Pitcairn GPU with a 768-shader configuration. As far as we are concerned, that’s actually too bad, since the benchmark numbers make such a chip a pretty interesting product. Also, judging by the overwhelmingly positive feedback our initial report generated, both on our own sites and around the Web, there is certainly a market for it. As such, this piece isn't a review so much as it's an exploration of a hypothetical component that doesn't exist (though we'd certainly welcome it if it ever did materialize).

Our prototype with the vendor edited out. The final version will sport the 1024 SPs of a full Radeon HD 7850.Our prototype with the vendor edited out. The final version will sport the 1024 SPs of a full Radeon HD 7850.

But what makes this chip so interesting if it was never meant for public consumption? We don’t want to give too much away, but let’s take Crysis 2 as an example and look at the performance we get when we run the card through our benchmark using some settings that reflect what a board of this price range can be expected to face in real life.

Let's use a 1920x1080 resolution, 16x AF, 2x MSAA, Ultra details, and DirectX 11 mode for our example. A Radeon HD 7850, which can be found on Newegg starting around $250 (ignoring some rebate offers) takes those settings in stride, achieving a comfortable 41 FPS, on average. The next card down in AMD’s current portfolio, Radeon HD 7770, which sells for about $100 less, is not playable under the same load, averaging around 28 FPS. That leaves a gap of 13 FPS and $100 separating playability and disappointment. Doing a bit of math, the halfway-point between the fastest 7700- and entry-level 7800-series SKU gets us a price tag around $200 and a frame rate around 35 FPS. Lo and behold, the engineering sample in our lab comes in at a respectable 36.5 FPS!

AMD insists that there is no product planned in between the Radeon HD 7770 and 7850. The company is adamant that the 768-shader Pitcairn part was only intended for high-level validation and board characterization. And, at the end of the day, this might go down in history as a cool piece of technology that never makes it out of one site's testing lab.

However, we're certainly allowed to have the opinion that AMD has a gap in its line-up that we think it should be filling rather than ceding to the competition without a fight. And that’s why this GPU is so interesting (aside from the benchmark results that enthusiasts like us find fascinating in their own right). The comments on our news report showed that a card based on a chip like this would definitely appeal to gamers on a limited budget that currently can’t find the right card. While it’s not really our job to find and point out business opportunities to the companies whose products we review, we believe this card would find an audience, and we hope AMD takes note and listens to your comments!

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  • woe96
    i want one, that a amazing place in performance and probably only be $200
  • s3anister
    I would never buy this card for myself but I would find myself recommending a 1GB model, like you mentioned, to family and friends. If the price is right AMD could have a great mid range card.
  • wolley74
    while a nice card, the 6850 is incredibly close and nearly $60 cheaper, the only thing is it does consume more power
  • borden5
    oh man that single slot would be really nice for people who wanted small factor rig
  • slomo4sho
    Wouldn't 2 7750s in crossfire perform better than this rig and also consume less power at the ~$200 price point?
  • erraticfocus
    Slomo4shOWouldn't 2 7750s in crossfire perform better than this rig and also consume less power at the ~$200 price point?

    Maybe, depending on your local market, but the single slot and price point is the whole point to this...
  • Say hello to the AMD HD Radeon 7790.
  • pwnorbpwnd
    This card would be an AMAZING pick for an HTPC, Single slot, Low power, 2gb DDR3 for HDTV's, not to say 1gb wouldn't be okay. But really AMD, do it up! All of this positive feedback is great reason to make a crippled 7850!
  • weatherdude
    This card performs great and a 1 GiB version selling at ~$200 would fill in a very large gap in the market. It would only make sense if AMD is cooking up something they'll likely call a 7830 to do just that. I guess though it would differ from this engineering sample if they're so insistent that they aren't bringing it to market. Maybe it'll have less texture units or ROPs.

    Still this card with 1 GiB at ~$200 would be pretty sweet AMD *nudge* *nudge*.
  • Doesn't the 7770 have 40 Texture Units and not 14?
  • atikkur
    now bring the game..
  • blazorthon
    A "7830" with 1GB of VRAM priced to compete with the 6870 or 6930 (if you have that in your country, the USA doesn't) 1GB cards would be great. If anyone wants a new card between the 7770 and 7850 in performance (basically, between a just short of a 6850 and just short of a 6970), then they're screwed because there is no middle point. They have no choice other than buying an old 6870, 6930, or 6950.

    With a 1GB model at $185 to $195 and a 2GB model (2GB is far better than 1GB for Crossfire setups at higher resolutions/quality/AA/AF) at $210 to $220 would be good. Also, 7830 is the best name for this, at least in my opinion. All that would need to be done is bringing down the power usage a little (need is a strong word for this, that it is lower than the 7850 is still a great improvement over the 5830 and 6790 fiascoes). I would like to see a 100 to 110 watt TDP, rather than a 120w TDP (sure, TDP does not equal power usage, but still). Even without doing that, it still uses less power than the 6870, so it's acceptable. However, if Nvidia makes a competing card (looks like they will), then Nvidia would probably undercut it by at least 15 to 20w.

    Regardless, come on AMD, release this as a 7830 or something such as that! It's a great card and it fills a market that is almost desperate for a refresh!

    NivalisSay hello to the AMD HD Radeon 7790.

  • x3style
    Give single slot card so we can revigorate our minimalistic solutions with extra power for when diablo III arives.
  • blazorthon
    wolley74while a nice card, the 6850 is incredibly close and nearly $60 cheaper, the only thing is it does consume more power

    You mean the 6870, not the 6850. If more games were included, we would see the 6870 closer to this hypothetical 7830 most of the time. Keep in mind that Tom's tested a 2GB model, so you would have to compare it's price against the 6870 2GB for a fair comparison, not the 6870 1GB.
  • manu 11
    want one, cant afford the 7850! $160 should do it justice.
  • Rattengesicht
    Do it AMD ! You know you want to ;-)
  • Maximus_Delta
    I really like this sort of investigative journalism. Two thumbs up.
  • Darkerson
    I guess we'll just have to wait and see if they change their mind and release it eventually. Would be a nifty little card with a more affordable price tag.
  • esrever
    Anyone else notice that the 7970 and the 680 are trading blows? And it seems that they are pretty even?
  • Allan_01
    this should me HD7790
  • youssef 2010
    ArticleThere is one small change to note: as a result of the wear and tear associated with constantly switching out graphics cards, the x16 PCIe slot on our Gigabyte Z68X-UD7 B3 literally came off the board. We are using the Gigabyte Z68X-UD5 B3 in its place, giving us identical performance.

    Ouch, has that ever happened to another board in your lab?
  • youssef 2010
    I think AMD should mass produce the GPU. After all, it the company that invented the sweet spot strategy.
  • redeye
    why not just send it back?. but since you love Nvidia, it will not make a difference if the next new AMD card is on a slow-boat-from-china...
  • ScrewySqrl
    pretty much right where I predicted it would sit in my comment on the original news article yesterday. This would be a GREAT card in the $180-200 price point.