So, you lads might be thinking of setting up a Crossfire pair for games and scoring higher on benchmarks. But unfortunately, while those of you have saved enough money to buy one HD7900 series card, most owners don’t have enough money to shell out for a second one, making a Crossfire setup too expensive for single-card owners. But what if there was a cheaper way to do it? You can’t pair a HD7800 series card with anything from the HD7900 family ordinarily, but there is one new card that changes that – the HD7870 LE, as TechpowerUp! discovered this weekend.
Firstly, AMD has been the only option for those who own dual-GPU products like the HD7990, HD6990 and HD5990 to run the card in Crossfire with another one from the same family that only has a single processor. Back in the day you couldn’t run triple Crossfire easily on most boards, but enthusiasts who already had a HD5990 discovered that the HD5870 and HD5850 made the perfect partners. You can mix and match cards in the same family, but the array’s ability will be limited somewhat by the slowest card in the group. Later on this option appeared again, giving HD6990 owners the option of tagging in the HD6970 or HD6950 (which could be unlocked to an HD6970 through BIOS mods) for better framerates.
The HD7990, on the other hand, isn’t even a model officially supported by AMD because it would cost the company far too much to manufacture on its own. AMD did, however, disseminate reference designs of the card, even though it typically requires three 8-pin PEG connectors and sucks up over 250W of power while gaming. Only a handful of companies actually make it and they’re all owned by the insane Club 3D. Club 3D’s been in bed with AMD as a graphics partner since 2001, so they’re usually the brand that does the things that AMD can’t, like actually build and market the HD7990.
At its core, the HD7990 is just two HD7970 chips paired together with a PCI-Express bridge. Each still has their own 384-bit bus and carries 3GB of RAM and a slightly lower TDP because the chips are clocked to lower speeds. There are even versions of the HD7990 that use the GHz BIOS, putting both chips at 1GHz frequencies by default with the PowerTune ability. But what hurts most is that you’d have to stump up a lot of money to put in another card to compliment it, using either the HD7970 or HD7950. For most owners, putting in another HD7990 isn’t an option, mostly because its extremely expensive and doesn’t come in stock often. But what if there was a cheaper option?
The HD7870 LE is a special, limited-edition chip that AMD released to partners a while ago that changes things a bit. Its a cut-down HD7950 sporting 1536 shader cores, 32 ROPs and default clocks of 975MHz and typically falls into the $270 price range, just edging over the HD7870 but not creeping in the area the HD7950 occupies. It also ships standard with DDR5 RAM running at 6GHz on a 256-bit bus. Club 3D’s HD7870 jokerCard is one such LE version and its one of the first on the market. It may read in the BIOS that it’s a HD7870, but that didn’t stop TechpowerUp! finding out if it would match up with an HD7900 series card – and it did!
Caveats? Well, it won’t, however, pair up with a HD7870 or HD7850 card, for starters – these two are based off AMD’s Pitcairn design and won’t link up to any other card outside of their family. Being that the HD7870 LE is Tahiti-based, like the rest of the HD7900 series, its a welcome cheaper upgrade if you can’t find the HD7950 in stock. You could even grab two of these and pair them together and you’d land up with more or less the same performance as a Crossfire pair of HD7950s. It doesn’t sport 3GB of RAM by default, so a Crossfire pair with a HD7970 would be limited to just 2GB of VRAM. Its also struck with somewhat of an efficiency issue consuming an average of 30 watts more under load, leading me to believe that these are fused off HD7950 dies that didn’t make the cut in the first place.
AMD needs to do things like this more often, I think.
You also won’t find many of these in stock, not unless AMD decides to use this design over the regular HD7870 (and given the efficiency issue, I don’t think it will). Overclocked, it’ll match the performance of the HD7970 occasionally, while generally being faster than a stock HD7950. At $270, its a bargain for buyers looking for something better than a vanilla HD7870. Keep your eye out, folks.