- Thursday , December 22, 2011
- Brent Justice
AMD Radeon HD 7970 Video Card Review
The new Radeon HD 7970 marks the launch of AMD's next generation video cards. The Radeon HD 7970 represents the fastest single-GPU video card from AMD with a new architecture. We will evaluate gameplay performance and compare it to the previous generation, as well as the competition, in single-display and Eyefinity resolutions.
AMD's much anticipated next generation GPU series is finally here, today we can reveal to you that AMD is going to have a Radeon HD 7000 series of GPUs. The Radeon HD 7000 series of GPUs will be the successor to the Radeon HD 6000 series, offering a new architecture, new specifications, more features and hopefully better performance at the respective price points.
While a whole slew of Radeon HD 7000 GPUs will be coming, they aren't all being launched yet. In fact, we only have official specifications on one of AMD's new 7000 series GPUs, the high-end fastest single-GPU video card, the new AMD Radeon HD 7970. This, right now, is the only video card we have information on, and have in hand to perform gameplay performance testing with. The AMD Radeon HD 7970 is the video card that is being launched today. All of the other Radeon HD 7000 series based video cards will be launched at later undisclosed dates in 2012. Expect to see the next one down the branch released sometime in January 2012.
The AMD Radeon HD 7970 is AMD's new flagship video card, sporting the fastest single-GPU AMD has created to date. The AMD Radeon HD 7970, as the name suggests, is the successor to the Radeon HD 6970. The AMD Radeon HD 7970, however, is launching at a much higher price than the Radeon HD 6970 debuted at a year ago. In December of 2010, the Radeon HD 6970 was launched with a price tag of $369. The new AMD Radeon HD 7970 launching today, is going to sport a MSRP of $549. That is nearly a 50% increase in cost over the debut of the Radeon HD 6970. Right now, Radeon HD 6970 video cards have dropped to as low as $300 with rebates. Therefore, there is a wide gap in price between the previous generation Radeon HD 6970, and the new video card at this point in time.
AMD's reasoning behind the price is actually to compete with NVIDIA's GeForce GTX 580 offering. In November of 2010 the NVIDIA GeForce GTX 580 launched with an MSRP of $499. The current pricing strategy of the AMD Radeon HD 7970 places it $50 above MSRP of the current competition. Currently, GeForce GTX 580's can be found as low as $469 with rebates. With the Radeon HD 7970 being more expensive, it simply must deliver a noticeably better gameplay experience to compete, and that is what we are going to find out today by using a more expensive overclocked Galaxy MDT GeForce GTX 580 video card in this evaluation. Current pricing on the Galaxy MDT GeForce GTX 580 has it about $50 more expensive than the Radeon HD 7970, but it is also overclocked, and should be a great test for the new video card.
AMD Radeon HD 7970
The AMD Radeon HD 7970 is part of AMD's "Southern Islands" product line, with the 7970 belonging to the "Tahiti" class of GPUs. Below that, in time, we will see GPUs based on AMD's "Pitcairn" and "Cape Verde" class of GPUs as well. There are several new features that AMD is anxious to show off. Firstly, the Radeon HD 7970 is a 28nm GPU, using this new process technology. The Radeon HD 6970 was based on the 40nm process. This is a large leap in process technology, and ensures higher performance, more power efficiency and potentially better yields. The big question on everyone's minds is can AMD get enough 28nm GPUs churned out to fill the market? We will just have to wait and see. While Radeon HD 7970 video cards will be trickling out through Christmas, they won't fully be out in retail until January 9th.
Beyond 28nm, AMD has created a whole new architecture with the Radeon HD 7000 series, which actually resembles something already familiar. AMD is also introduced PCI-Express Gen3 (3.0) support with this video card. The Radeon HD 7970 is also the first video card to fully support DirectX 11.1. DX11.1 will be in Windows 8, and Microsoft will make a download available to Windows 7 users.
All of the specifications on the Radeon HD 7970 are listed above. At $549 it better pack in new features and a heck of a lot of performance. We can see that there are 2,048 Stream Processors in the Radeon HD 7970. This is compared to 1,536 in the Radeon HD 6970. At first glance, this may not sound like a dramatic improvement, but keep in mind the architecture is completely different, it is not VLIW4 like the Radeon HD 6970. We will discuss the new architecture below.
With 2,048 Stream Processors the Engine Clock is set at 925MHz, versus 880MHz with the Radeon HD 6970. The Texture Units have been increased from 96 on the Radeon HD 6970 to 128 with the new Radeon HD 7970. These facts alone mean a higher compute performance and texture fillrate. The ROP and Z/Stencil count remain exactly the same, with 32 ROPs and 128 Z/Stencil. AMD is betting on the new faster memory bus to improve ROP performance here, instead of just flat out giving us more ROPs.
Speaking of memory, AMD has gone with a total 384-bit wide memory bus, which consists of 3-dual 64-bit paths. What this means is that the memory modules are now arranged similar to the GeForce GTX 580, by way of the inherent nature of a 384-bit bus. AMD has outfitted 3GB of GDDR5 on the Radeon HD 7970, which is 1GB more than the HD 6970, and 1.5GB more than the GeForce GTX 580. By way of this bus interface, we won't see 2GB versions, it can only be either 3GB, or 1.5GB with this memory bus. Thankfully AMD chose the high-road and put 3GB of memory on by default. This is welcomed, and we are glad they did not go with the lesser 1.5GB. The memory runs at the same 5.5GHz as the Radeon HD 6970, but because of the memory bus improvement the bandwidth has shot up to an amazing 264GB/sec of bandwidth versus 176GB/sec with the HD 6970.
Amazingly, with this increase Stream Processor count, clock increase, texture unit increase, memory bus improvement and performance, the board power remains the same as the Radeon HD 6970! AMD has also improved cooling with this video card. AMD is using a larger diameter fan, with new blades which creates higher CFM at lower RPMs. AMD is using a 6th generation vapor chamber heatsink design. AMD has also increased the exhaust port on the back to exhaust more heat. Similar to the Radeon HD 6970 AMD give us dual-BIOS controls to let us create our own BIOS flashes, all while still maintaining a factory default setting.
AMD feels it is time to create a new architecture, developed with the intention of having a high compute architecture that is capable of being scalable and very flexible. The previous generation Radeon HD 6970 utilized the VLIW4 architecture, and the lesser 6000 series used VLIW5. AMD's new architecture is being called Graphics Core Next, or GCN for short. If you look closely at the architecture, you will find that it actually reminds us of NVIDIA's GF100 architecture, also known as Fermi. As you can see above, there are GCN Compute Units which can execute multiple kernels at once. There is a vector unit (4x SIMD-16) and Scalar units, along with the scheduler and texture units. There are also cache units and Local Data Shares.
There are 32 GCN units in the Radeon HD 7970 with dual-geometry engines, 8 Render Back-Ends capable of 32 color OPs per clock and 128 Z/stencil. There is 768KB L2 cache and AMD is leaving it to the fast 384-bit memory bandwidth to offset the 32 ROPs per clock performance. This along, should give us faster ROP performance, even though they have not given the HD 7970 more ROPs. All of this is made up of 4.3 billion transistors. 28nm was definitely needed to pack in this many transistors.
Tessellation performance was generally a low-point for performance with the Radeon HD 6000 series, especially when compared to the GTX 580. AMD has improved Tessellation performance by increasing vertex re-use, making off-chip buffering improvements and providing larger parameter caches. AMD is claiming a 4x improvement to throughput for Tessellation compared to Radeon HD 6900 series.
Though texture filtering was great with the Radeon HD 6000 series, AMD has sought to make it even better with the Radeon HD 7000 series. There was an issue with the Radeon HD 6000 series that sometimes produced a shimmering or crawling effect in the distance on far out textures on certain planes. AMD has improved filter kernel weights that should reduce this shimmering or crawling seen on textures. After having using the new Radeon HD 7970, we can state that AMD has indeed improved and fixed this issue.
In our testing, we found Skyrim to show this issue the most on rocky roads as we are traveling throughout the world on the Radeon HD 6970. We did see this shimmering and crawling. When we installed the Radeon HD 7970 it was gone, and the texture quality was better. It isn't visible in all games, and Skyrim seemed to be the worst offender, in fact, the only offender, we experienced in our testing. AMD has certainly tackled this issue, and texture quality should now be near perfect with the Radeon HD 7970.
AMD has created a new and exciting technology called ZeroCore power. The goal of this technology is to put the GPU, or parts of the GPU to sleep on long idle scenarios. In fact, the GPU can go into such low power that the fan itself on the video card will turn off, saving you even more power. This only occurs during a very long idle time, or blanked screen state. All of this is handled automatically. Part of ZeroCore technology that is really exciting for hardware enthusiasts is how it interacts with CrossFireX.
When you have multiple video cards installed, ZeroCore power is able to turn off un-used video cards at idle when not in use. This means, you could have 4 video cards installed, but if you are idling, all three could turn themselves off basically, and power down the fans, leaving only the primary video card running, and in time, even the primary card can power down. This should make running two or three video cards a much more power and temperature friendly feat. When the video cards are not in use, they will power down, and turn the fans off. When needed, they will instantly kick on when you go to game. This has huge potential for saving power and reducing temperature in extreme CrossFireX systems.
DX11 and Overclocking
As we stated, the Radeon HD 7970 is the first DX11.1 capable video card. DX11.1 however is not all that exciting. DX11.1 will allow target independent rasterization, and native stereo 3D support and more flexible interoperability between graphics, compute and video. It isn't really anything to get overly excited about, at this point, DX11.1 is a check box feature, one which AMD can mark off the list at this point in time. Windows7 and 8 users will have DX11.1.
The default core clock is 925MHZ, but AMD states this video card should be able to be overclocked past 1GHz. We have heard that in-house testing has resulted in overclocks as good as 1.1 and even 1.2GHz, all at default Voltages. That means, as add-in-board partners create custom video cards, with Voltage Tweaking, we might see some well above 1GHz overclocking ability. We didn't have time to test overclocking in this evaluation, but we will dive into that in future articles.
Radeon HD 7970 Pictures
You might expect, with all of these new features, performance improvements and specifications that the Radeon HD 7970 would be a huge video card. In actuality, it is exactly the same size as the previous generation Radeon HD 6970. In fact, the shroud covering the heatsink actually seems smaller. The design of this video card is exactly the same as the HD 6970 in shape and form. It is 10.5" long, same length as a Radeon HD 6970.
On the opposite side of the exhaust port, there are some accent slits, but these are not actually functional for air intake. The Radeon HD 7970 takes its air from the fan and expels it out the back. What's different is that AMD has a larger fan on this video card, with new blades, and a wider exhaust port. Other than that, if it wasn't for the shape of the shroud, you'd mistake it for a Radeon HD 6970.
The AMD Radeon HD 7970 requires one 8-pin PCI-E power connector and one 6-pin connector, same as the Radeon HD 6970. This is good news, if you are running a GTX 580 or HD 6970 now, you will have no problem running this video card, no extra hardware is required.
The AMD Radeon HD 7970 supports CrossFireX in dual and triple form. There is a BIOS switch atop the video card that allows you to flash your own BIOS to the unprotected position, and then switch back to defaults in the protected position. This is a powerful feature for hardware enthusiasts who want to tweak their video card and get the most performance possible, while still having a safeguard incase it doesn't work.
The AMD Radeon HD 7970 does lose one DVI port by extending the exhaust port. Two mini-DP and HDMI port are supported. Maximum displays supported from this video card is six. Because of the loss of a DVI output connector, AMD will be including a HDMI to DVI and mDP to DVI adapter with this video card, so you won't actually lose that DVI port if you use the adapters included.
Above is a comparison to a stock Radeon HD 6970. You can see that it is exactly the same size. In fact, it appears a bit smaller thanks to the slopping curved tapered back-end of the video card shroud. The Radeon HD 6970's shroud is rectangle, the HD 7970's shroud is more curved and rounded off.