AlienBabelTech is not under NDA with AMD for the upcoming launch of their new architecture HD 7970 this coming Thursday, December 22. The HD 7950 is set to launch on January 9, the same day that stock will be hopefully available for both video cards. We are pleased to share with our readers what we have learned about these new video cards. The leaked image below is from OBR Hardware. It is the approximately the same ten inches long as the current HD 6970/6950 reference design.
AMD has had a major realignment of their company since the FX series of CPUs were met by less than satisfactory reviews. Most of their PR were fired and many now work for Edleman who is managing the HD 79×0 launch. This launch of the new HD 7900 series was originally scheduled for next month at CES but has been moved forward to December 22, 2011 as a part of AMD’s new strategy and to give their partners something to show off at CES.
The HD 7970, codenamed “Tahiti”, launches this Thursday, but without availability for purchase until January 9th when the HD 7950 launches. So it is a paper-launch until the day before CES and you will now have a preview of the reviews that you will get in a few days from the tech sites lucky enough to get one.
The HD 7970 launch is also one of the leakiest launches that AMD has had in recent memory, with most of their Press Deck freely available on the Internet. It has been leaked mostly by their partners and testers and even by some who actually have final editions of them in hand since last Friday. AMD had their Press Day in Europe on December 5 in London and Paris, and in other selected locations, and most of the information is now all over the Internet. However, we will do our best to gather it together all in one place to give you the most complete picture of the HD 7970 today.
Is Tahiti Short-lived?
The most interesting thing about this launch is that it appears that Tahiti’s HD 7970 may be short-lived. AMD’s 28nm yields are known to not be great and the specifications of the new GPU indicate that something strange is going on. The chip itself is quite complex with 4.3 billion transistors but its core only runs at a very conservative 925MHz. Most telling is that its performance is not that great except in DX11 games and especially in heavily tessellated scenarios – only about 25% faster than a GTX 580 overall.
Inside sources tell ABT that the HD 7970 is likely to be released much like GF 100 Fermi was. Originally, Nvidia released the hot-running and poor-yielding GTX 480 which was later reworked into the greatly improved GF110 GTX 580. It is pure speculation, however, that this new HD 7970 may ship with some parts disabled that may be enabled in a respin to meet the next generation of Fermi, the GTX 680 in Q1 of 2012.
At the very least, the HD 7970 is debuting very conservatively as a possibly new strategy from AMD’s new CEO. Timing is good as it shows up at the very end of the year so that AMD can now claim the fastest single-GPU crown, and it brings new life to their partners line-up in time for CES. Best of all, it gives AMD time to respin the chips into higher-performing video cards so as to meet the GTX 680.
We are also hearing that across the board, the stock HD 7970 is a bit disappointing as it only scores about 20-30% faster than the stock GTX 580 – well within reach of an overclocked GTX 580 and priced similarly at about $550. We are also hearing that in a few older DX9 games, it is not that much faster than than the previous generation’s HD 6970, and AMD’s emphasis will be on DX11 and heavily tessellated games.
It appears that the HD 7970′s extremely conservative 925MHz clockspeed comes with good overclocking headroom as a special grace. With the overclocked versions that AMD’s partners are free to produce, it may start to run away from the overclocked GTX 580.
Price for the HD 7990 is expected to be right around $550; certainly more expensive in Europe than in North America. The HD 7970 will be previewed by selected tech sites on the 22nd of December, but the card will apparently not be available for sale until the 9th of January when the HD 7950 is officially released.
Here’s an image of HD 7970 Crossfire as leaked by a member of Beyond 3D forums:
Interestingly, we see 8+6 pin PCI-E connectors with a provision also for a two 8-pin connectors. There are also 12 memory chips – 12 x 32-bit = 384-bit memory bus. Before we get into the technical details of the new HD 7970, let’s look at the architectural changes from the HD 6000 series and at more of the leaked slides from AMD’s press deck.
Changes in 7000 series
AMD’s Radeon HD 7900 series will use a brand new GPU built on the 28nm process, codenamed “Tahiti”. The top two GPUs – HD 7970 and HD 7950 each have 4.3 billion transistors. This represents a major break from their scalar VLIW-based computing since HD 2900XT was released, to GCN Quad SIMD.
AMD’s new buzzword is “performance per square mm” as it is higher than the old architecture for DX11 and GPU computing. In this case, the slide below appears to be comparing benchmarks which are much weaker on the HD 6970. And of course, no parameters for any tests are given. We look forward to the benchmarks on Thursday.
AMD intends to catch up to Fermi in GPU computing with this architecture and we can also expect greatly improved geometry and Tessellation. This new Tahiti GPU also supports DX11.1 and PCIe 3.0
And you are going to be hearing a lot of “firsts” – first to DX11.1 and first to PCIe 3.0 even though there are no DX11.1 games yet nor will next year’s upcoming dual-chip HD 7990 saturate even PCIe 2.0
Tahiti features 2,048 stream processors, all of which are enabled on the Radeon HD 7970. These stream processors are arranged along 32 computing units, each with 64 SPs. It has a 384-bit wide memory interface which provides bandwidth around 260 GB/s. The stock HD 79×0 comes with 3 GB of GDDR5 memory using twelve 2Mbit memory chips.
In the above picture posted by VR-Zone, the 5+1 phase PWM is visible. We note that the Tahiti die is rotated 45 degrees and partially covered by a heat-spreader although the die itself is exposed to the heatsink. It’s a big GPU, though a bit smaller than Cayman. The card features two CrossFire connectors as well as the dual BIOS toggle switch just like the HD 6900 series.
Turkish web site Dominhaber originally posted these specifications with just one significant error regarding the ROPs.
- 4.50 billion transistors, die-area of ~380 mm², built on TSMC 28 nm process
Advanced GCN 1D architecture
2048 1D processing cores
128 TMUs, 48 ROPs
384-bit wide GDDR5 memory interface, clock slightly below 1 GHz, target bandwidth of 240~264 GB/s
6pin + 8pin power connector required
PCI Express Gen 3.0
DirectX 11.1 support
Another likely AMD PR slide (with misspelled “embargo”) posted by OBR-Hardware confirms that there are 32 ROPs, not 48. In the new GCN architecture, ROPs are no longer directly coupled to the memory-controllers.
Here is a handy chart which compares the HD 7970 to the HD 6970
Consuming less than 3W at idle is an amazing new feature, considering that the HD 6970 consumes about 20W. As you can see, AMD is pleased to compare the HD 7970′s idle wattage against their competitors using QuadFire as an example.
AMD reference board design still retains their signature black and red color scheme. Even the PCB is black. The cooler shroud is curved and a pair of HD 7970s appear to be designed to work better together in CrossFire, both acoustically and with better airflow between the cards than with the relatively noisy HD 6900 series.
Display connectors include DVI, HDMI, and two mini-DisplayPort connectors. The display ports are all located in one PCIe slot area so designed to exhaust hot air from the second slot and it would be ideal for watercooling. Board partners are evidently required to include HDMI to DVI and active-DP dongles with the video card.
Even though the HD 7970 is clocked conservatively to increase AMD’s yields, the picture will change dramatically when the HD 7970 is overclocked from its base of 925W with its TDP going well over 300W. AMD expects this GPU will clock “well in excess of 1GHz”. This ability to overclock the HD 7970 is its strongest feature and we can expect AMD’s partners to take full advantage of this overclocking headroom to distance the HD 7970 from even the highly overclocked GTX 580s. ABT will be at CES and we will bring you images and specifications of these new designs.
The HD 7970 is based on GCN architecture. According to the slide, it packs 32 ROPs and 128 texture units. ROPs are decoupled from the memory controller in this new architecture. Dual geometry engines are featured and an impressively large L2 global cache of 768KB.
With Tahiti’s new GCN architecture, each CU cluster accesses their own TMU/ROPs directly and there is a bigger cache than with VLIW, including a large global L2 cache. In VLIF architecture, the ROPs were shared and an interface regulates the access.
Even so, the HD 7970 still appears to be a bit unbalanced as though some of the function units are disabled, but that is pure speculation. However, it wouldn’t surprise us to see a “refresh” and a respin of the HD 7970 if/when the GTX 680 turns out to have more performance than AMD is expecting, early next year.
We are getting reports that the HD 7970 is about 20-30% faster than the GTX 580, depending on the game or benchmark used – and faster if it is overclocked. According to the AMD leaked slide from Dominhaber, tessellation is improved at least 1.5 times over the HD 600o series and we expect the most favorable AMD benches to be DX11 and heavily tessellated. There will be no emphasis on DX9 gaming as far as we can tell.
These most favorable benches would include Battlefield 3 at very specific benching conditions. It is very doubtful that the stock HD 7970 will be 1.4 times faster than the GTX 580 across the board. They will be lucky to get over 25% according to what we are hearing now.
The HD 7970 launch looks to be interesting as AMD again strives to be “first” with their new generation, ahead of Nvidia. They appear to have a good short-term strategy as it gives AMD the single-performance crown right now and a new line-up to showcase at CES for themselves and for their partners with a chance to build good momentum. Is the HD 7970 a “stopgap” video card? Well, only the future will tell us if AMD’s new CEO has winning strategy or not.
We hope you enjoyed our preview of the HD 7970. Many thanks to the leaks posted at VR-Zone, Dominhaber, Expreview and other tech sites. Of course, you read it all put together first at ABT. We also brought you the first pictures and accurate specifications of the HD 5970 before it was released. Naturally we eagerly look forward with you to the official reviews on Thursday. In the meantime, join us on ABT forum as we will continue to update you with the very latest news as it comes in.
Next up, due to be published this week at ABT is a review of the Galaxy MDT GTX 560 and another part of our ongoing S3D series – 3D Vision 2 brings a new level of immersion to Trine 2 and Batman: Arkham City. After that, more hardware reviews as we prepare for CES in Las Vegas.
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