Author: Chris Ledenican
Editor: Howard Ha
Publish Date: Wednesday, February 15th, 2012
Originally Published on Neoseeker (http://www.neoseeker.com)
Article Link: http://www.neoseeker.com/Articles/Hardware/Reviews/AMD_HD_7770_7750/
Copyright Neo Era Media, Inc. - please do not redistribute or use for commercial purposes.
AMD's Southern Island graphics cards have been aggressively hitting the market and while there have been some driver issues, the overall reception for the new cards has been mostly positive. That's because ultimately both the Radeon HD 7970 and HD 7950 push more pixels than their HD 6000 series counterparts while also offering better performance-per-watt and overclocking headroom as well. Today Neoseeker will be examining the latest iteration of the Southern Islands family; the Radeon HD 7770 and HD 7750.
Like their older siblings, both of these new graphics cards are based on AMD’s Graphics Core Next architecture, albeit slimmed down in comparison to Tahiti. This of course reduces the overall performance, but with the trimmer architecture, AMD is able to retail the 7770 series at more cost effective MSRP. This places it in a market sweet spot previously dominated by the HD 6770 and HD 6750.
The retail pricing for the HD 7770 and HD 7750 sit at $159 and $109 USD, respectively. At this price they sit just a bit higher than the Juniper architecture, but with the GCN design they should offer better gaming performance, more efficient parallel computing, Eyefinity 2.0 support, PowerTune technology, ZeroCore Power and Gen 3 PCIe support.
Without further ado, let’s jump right into the hardware of the new Cape Verde graphics cards and see if they really are the prescription needed to enhance, well…performance. For more info on your prescription of Verdetrol check out their website to see if it is right for you.
AMD's Graphics Core Next is a scalable architecture designed to be optimized for both graphics horsepower and compute power. Since the design is scalable, the Cape Verde graphics cards use the same architecture as the Cayman based graphics cards, albeit scaled down as mentioned on the previous page. Looking at the HD 7770, the GPU is compiled of 10 Compute Units giving it 640 streaming processors, 4 Render Back-Ends, 512KBs of read/write L2 cache, and a 128-bit memory bus all running on a PCI Express 3.0 x16 bus interface and packing in a total 1.5 billion transistors. The GPU also includes a single geometry engine that has its own Rasterizer and Render Back-End unit, but share the 10 Compute Units. You can basically think of these Geometry engines as having dual cores inside the GPU.
For the most part, the HD 7750 has all the same internal specifications as the HD 7770 but with two fewer Compute Units. So instead of having 10 compute units and 640 streaming processors, it has 8 compute units and 512 streaming processors. Of course this means it will come with lower clock frequencies, but internally there is little separating the two products.
As mentioned earlier, the Southern Islands GPU is designed to work as both a graphics and compute engine. This is due to the ACE engine which posits three devices in one GPU that are completely asynchronous from one other: the graphics pipeline, the direct compute pipeline and two parallel pipelines inside the GPU. Each of these run independently and asynchronously to the primary graphics pipeline. This allows the GPU to process an intensive compute simultaneously with the graphics pipeline while it is running an intensive 3D application, and maximizes the utilization of the available compute power. In total the HD 7700 has up to 1280 GFLOP/s single-precision floating-point performance, while the HD 7750 has 819 GFLOP/s single-precision floating-point performance.
On top of this, all of the GDDR5 memory is protected by single error correction and double error detection when used in a compute environment. All the internal SRAM has the same capabilities, and also have ECC data protection.
As many are wondering exactly how the efficiency of CGN compares to VLIW4, AMD has stated that we should see more performance per millimeter with the GCN architecture than what was available in previous generations. According to Eric Demers from AMD, this should represent a peak physical improvement of up to 7 to 7.5 times over previous generation architecture, like that used in the Radeon HD 6970. The Tahiti architecture also includes an improved Gen 9 tessellator unit that increases the tessellation throughput via more efficient vertex re-use, larger parameter caches and improved off-chip buffering. All of this gives the GCN architecture up to 4 times the throughput compared to the Radeon HD 6900 series.
The basic compute unit includes all the instruction, wavefront and scheduling; essentially this unit can be thought of as its own core. Each compute unit has four sub-units that run a way-front of 64-bit vector lanes over four cycles that are completely independent of each other. This is a huge departure from the VLIW engine, which had 5 or 4 math units that executed the individual instructions in a parallel process. Since the new GCN architecture runs fully scalar, it eliminates the compilation issues of the VLIW design.
In addition, the scalar runs in parallel to the unit and can issue instructions of its own, allowing complex operations to be moved to the scalar for improved efficiency. The unit also includes a 16KB L1 cache that has both read and write functions allowing the textures to run through the cache, as opposed to entering the cache to be processed and then passed on to the back-end before being exported back into the cache. This function can now be handled exclusively though the L1 cache via the read/write functions.
Moving over to this form of computing doesn't necessarily translate into improved graphics performance, but since the VLIW compiling was not necessary efficient, it will improve the total compute power, i.e. parallel processing of the GPU. The compute unit on the other hand has four independent wavefronts running in parallel, as well as a scalar programing model at the lane level to ensure that all instructions running through the GPU automatically work. This eliminates all port conflicts, simplifying the compiler and instructions, thus improving the compute performance dramatically.
When it comes to the memory, each L1 cache has 64 bytes of bandwidth per clock and the HD 7770 has a total of 32, giving it up to 2TB/s of bandwidth. As mentioned before, each L1 cache has both read and write functions, something new to the Southern Islands architecture. However, each L1 still has a L2 cache to fall back on, but the L2 also now includes both read and write functions. The HD 7770 come packed with twelve L2 caches that feed back into the L1 cache which are also 64 bytes per clock.
The GPU also includes a 16KB instruction cache and 32KB scalar data cache that are shared per four compute units, which as mentioned earlier are also backed by the L2 cache. Additionally, each compute unit has has its own registers and local data share. There is also a global data share unit that works as a manage buffer on the chip to allow sharing between any wavefront on the chip.
The Southern Islands architecture also includes a texture mapping technique called Partially Resident Texture, or PRT. Essentially what this feature do is take advantage of all the memory hardware available, and turn the local frame buffer into a local texture cache. So, what does this mean? First, the local graphics memory can behave like a hardware-managed cache where texture data can be streamed in on demand. This prevents stuttering as the pages are brought in, and texture stream has the ability to handle the process more efficiently.
PRT also Improves the memory efficiency and image quality with very large, detailed textures. This allows for texture sizes up to 32 TB (16k x 16k x 8k x 128-bit), done by turning the textures into 64KB chunks that are dynamically selected and loaded into the memory as needed. So, essentially the textures that are not going to be displayed are not loaded. PRT also translates through the page table's every request. The data is rendered if it is available, and if not the application can manage the textures instead. This allows it to dynamically opt to use lower resolution bitmaps which will make the textures slightly blurry, but there will be no lag time in these situations.
Like the HD 6900 series, the Southern Islands graphics cards come equipped with AMD PowerTune technology. PowerTune is basically a means to set a predefined TDP by adjusting the clock speeds in real time. The way in which PowerTune is utilized is very different than the on-board regulation chips used on NVIDIA’s GTX 500 series. NVIDIA’s power management system monitors the power coming from the rails, while AMD’s technology instead relies on performance counters that are embedded throughout the GPU. These performance counters have an internal algorithm that dynamically calculate how much power is being used, and adjust accordingly. This allows PowerTune to maintain the power draw at the predefined level, effectively eliminating huge surges in power from occurring. Since games operate at a lower peak power rate than benchmarking applications such as Kombuster, in-game performance will not be negativity affected.
AMD has also introduced a new feature called "Zero Core Power" which maximizes the idle power consumption of the board. When a discrete GPU is in a static screen state, it works to minimize idle power by enabling a host of active power saving functions including (but not limited to); clock gating, power gating, memory compression, and a host of other features. However, GPUs with AMD’s exclusive ZeroCore Power technology can take energy savings to entirely new heights by completely powering down the core GPU while the rest of the system remains active.
Along with the changes to the architecture, AMD is also introducing Eyefinity 2.0. For the most part, the changes are being made at the driver level but there is one new feature being added to the Southern Islands graphics cards.
The new features gives Southern Islands cards the ability to simultaneously output multiple, independent audio streams. Essentially this means each video source that has the ability to support audio will have its own dedicated audio signal. This allows a single graphics card to connect to multiple displays, each having its own audio signal. In total the graphics card can support up to five audio signals. You can be fragging people on one monitor while watching your favorite show on another, also connected to the Southern Islands graphics card. The technology also follows the video so if the source changes, the audio seamlessly switches to the other device as well. This is actually an interesting feature that really pushes the expansion options of the Radeon series forward.
The next feature is one that we have been hoping would come along for some time now, namely the merging of Eyefinity and HD3D. Unlike the previous feature, having a Southern Islands graphics card is not required to run Eyefinity in 3D. Instead this is a simple driver update that will enable the feature for all graphics cards that already support both technologies. Stereoscopic 3D technology from both AMD and NVIDIA is still niche at best, but we are glad AMD is moving forward and taking Eyefinty to its next logical step.
Another driver fix is the addition of flexible bezel compensation. The image below should give you a good idea of what this is all about. Essentially, it allows anyone to pair three non-identical monitors together and not have to worry about the images not lining up. Instead, the user can adjust the displays and still have the on screen image align perfectly across the displays.
AMD has also added a task bar positioning feature. Anyone that uses Eyefinity knows that previous drivers pushed the main desktop display to the leftmost screen. With this new positioning feature, the user can now pick which display the task bar is set to. Again, this is a huge improvement over the previous generation Eyefinity, and will make using this technology more convenient as the main desktop can now be manually configured to fit the individual needs of any Eyefinity user.
Eyefinity 2.0 also includes a custom resolution feature allowing the display resolution to be manually set to best fit the users' needs. While most gamers will be happy simply setting the resolution to 5760x1080, there are a handful of people that prefer even greater customization. The new Eyefinity 2.0 adds support for 5x1 Landscape with 1920x1200 and 2560x1600 monitors. This means Eyefinity is no longer limited to monitors at or below 1080p, increasing the available display real estate even further.
First up is the AMD HD 7770, which sports the Cape Verde XT GPU. This gives it slightly more power than the Cape Verde Pro GPU, as it comes packed with 1.5 billion transistors built on a 28nm node with a die size of 123mm² . Internally the core features 640 streaming processors, 16 ROPS and 40 texture units. The core clock speed is set at 1000MHz (1GHz) giving the Cape Verde XT graphics card a total compute power of 1.28 TFLOPs. The HD 7770 also utilizes a 1GB GDDR5 fame buffer that is clocked at 1125MHz (4500Mb/s QDR), giving the HD 7770 has a total memory bandwidth of 72Gbps.
Turning to the visual style of the HD 7770, we can see it is similar physically to the Tahiti based graphics cards, but the PCB is dramatically smaller and the Cape Verde cards also adopt a propeller style fan design. While the card still uses the same red and black color scheme, the HD 7770 looks different from other Tahiti graphics as well as those from the previous generation Juniper series thanks to a centrally mounted fan. The HD 7770 does, however, include the same rounded shroud, which was designed to improve ventilation when the graphics card is being used in CrossFireX configuration. Also, since the PCB is smaller than the high-end cards, the HD 7770 measures in at just 8.25" which practically ensures the card that can fit into nearly any mid-sized chassis on the market.
The reverse side of the PCB includes a single CrossFireX connector, which indicates AMD is still only allowing their mainstream cards to be teamed in groups of two. In addition, the HD 7770 utilizes a PCIe 3.0 interface, and has double the maximum data rate over Gen 2.0, giving the card up to 32 GB/s of bi-directional bandwidth on an x16 connector. It is going to be hard for a single graphics card to saturate the PCIe Gen 3 interface with so much bandwidth, so the benefit will most likely only be noticeable with scaling multiple graphics cards together in CrossFireX configuration. However, since the HD 7770 is not a high-end graphics cards it will most likely not saturate the interface, even while running in CrossFireX.
The HD 7770 comes with a maximum PowerTune rating of 80 watts, so unlike Tahiti based graphics cards the HD 7770 does not require two power connectors. Instead it has a single 6-pin power connector at the tail-end of the PCB. This gives the board a total power capacity of up to 150 watts, which is a huge power buffer for overclocking. The HD 7700 series graphics cards also support "Zero Core Power". This reduces the load idle power consumption down to around 3 watts.
Looking at the stock video output configuration, we can see the HD 7770 features the same layout as the HD 7900 series. This gives the HD 7770 two Mini-DP 1.2 connectors, a single HDMI 1.4a connector and a Dual-Link DVI connector. The HD 7770 also uses the same non-stacked DVI design that was first introduced with the HD 7970. Essentially, this design improves the thermal performance thanks to improved heatsink ventilation. The non-stacked design also decreases the overall acoustics by reducing turbulence, making Southern Islands graphics cards quieter than the previous generation.. Also, just like the HD 7970, the HD 7700 will come bundled with a HDMI to DVI dongle, and mini-DP to DVI dongle that allow the card to support up to three DVI connections out of the box.
With the AMD HD 7770, AMD is continuing their improved Eyefinity and HD3D support. The card includes an HDMI port that uses the latest 1.2 standard, which allows it to support up to three monitors per port (via MST Hub) as well as AMD's HD3D technology. The middle HDMI 1.4a connector also supports 3GHz speeds with frame packing. Essentially this allows the connection to run the frames faster, which makes viewing images and playing games smoother across the board. The HDMI and DP ports can also be paired together to support HD3D Surround.
Since the HD 7770 has a TDP below 100 watts, using a thermal solution similar to those on the Tahiti based graphics cards would simply be overkill. Instead, AMD has included a smaller oval shaped heatsink that has a large aluminum fin array and a centrally mounted propeller fan. Additionally, the base of the heatsink is custom designed to match the dimensions of the Cape Verde GPU, while the mounting brackets ensure the heatsink applies enough force to properly cool the core.
We really like this design, as it should get the job done and still be quiter than the traditional AMD thermal solutions that use a blower style fan. However, very few consumers will ever see this particular design, because most of AMD's AIB partners are going to release HD 7770 graphics cards with their own custom design and thermal solution.
The printed circuit board of the HD 7770 is considerably scaled down in comparison to the high-end models. Looking over the PCB we can see there are four HYNIX memory chips on the sides of the GPU in a 2 x 2 configuration, a front mounted 3-phase VRM, and eleven solid capacitors throughout the PCB. Most striking though is just how small the die size is. At just 123mm² it is impressive how AMD managed to squeeze in 1.5 billion transistors, so even while the performance will be mainstream the Cape Verde chips should offer a ton of performance per millimeter. In comparison to the 365mm² Tahiti GPU, the Cape Verde die has been shrunk by over 50%.
Next up to bat is the Cape Verde Pro GPU. Like its older sibling, the Pro version was designed to fit into the mainstream market but the performance is slightly lower, allowing it to retail for a lower MSRP. The Cape Verde Pro core has the same 1.5 billion transistors and is built on a 28nm node with a die size of just 123mm². However, what is different is the GPU has only 8 compute units, giving it a total of 512 streaming processors, 16 ROPS and 32 texture units. With these internal specs and an 800MHz GPU clock, the HD 7750 has a total compute power of 819 GFLOPs. Additionally, the HD 7750 has the same 128-bit 1GB GDDR5 frame buffer as the HD 7770, though the clock speed on this model is set at 1125MHz (4.5Gbps QDR) to give it a bandwidth rating of 72Gb/s, same as the HD 7770.
Visually the style and length of the HD 7750 look similar to graphics cards traditionally found in the entry-level segment. This isn't necessarily a bad thing though. Essentially what this means is that with the 28nm node, AMD has been able to reduce the power requirement to fewer than 75 watts so there is simply no reason to include a large PCB or heatsink. That said, this design is not going to be seen in the wild to great degree because like the HD 7770, most retail models with have a custom design. One really nice aspect of this design is the size. At just 6.75 x 0.75 x 4.25 the HD 7750 can fit into any mid-sized case, and some SFF cases as well.
Like the other cards in the Southern Islands family, the HD 7750 utilizes a Gen 3 PCIe interface which gives the card up to 32 GB/s of bi-directional bandwidth on an x16 connector. In comparison to the HD 7770, the HD 7750 has a simple design that lacks add-on voltage regulation circuitry, CrossFireX connectors, and a power connector. While the board doesn't include a CrossFIreX connection point, the technology is supported for up to two cards.
Since the PowerTune rating of the HD 7750 is only 55 watts, all the power is supplied to the board via the PCIe slot, and not a 6-pin power connector. Like the HD 7770, the HD 7750 comes with support for AMD ZeroCore power, which reduces the long idle power rating to below 3 watts. With a power rating of just 55 watts and a host of power saving features, the HD 7750 should be one hell of a power efficient graphics card.
The HD 7750 marks the first graphics card in the Southern Island family to not include four video outputs standard. What is included is a single 1.2 DisplayPort output, a HDMI 1.4a output and a DL-DVI output. Even while the configuration is slimmed down from the more expensive models, the HD 7750 can still support Eyefininty, HD3D technology and 3GHz speeds with frame packing via the HDMI connector. So, while this graphics card has a low MSRP it still has plenty of video expansion options.
The heatsink design used on the HD 7750 is extremely simple. It has a large shroud that covers rows of vertical pillars and a centrally mounted fan. Again, this is more like a solution that would traditionally be found on entry-level graphics cards, but with the thermal envelope being reduced below 75 watts it should get the job done. Additionally, the heatsink has a large metal base with a contact area for the GPU and four screw holes to attach it to the core.
The only aspect of the graphics card that looks anything like what we have seen thus far from the Southern Islands graphics cards is the red stripe running down the middle.
The Cape Verde Pro PCB has a similar layout to that of the HD 7770. Located at the front is the VRM followed by the memory and the 123mm² Cape Verde Pro GPU. Once again there are four memory modules on the PCB that are manufactured by HYNIX and have a 256MB capacity. This gives the board a grand total of 1024MB worth of graphics memory running on a 128-bit bus. This gives it roughly the same memory interface as the HD 6700-series (albeit with a high bandwidth rating) so we aren't expecting any massive performance increases over the previous generation when it comes to gaming at high resolutions.
The HD 7770 and HD 7750 mark the third and fourth graphics card we have examined in the Southern Islands family. Up this point we have been impressed with just how far we have been able to push the 28nm design, and just like the reviews before we were impressed with the overall overclocking potential of the HD 7770.
To overclock both the cores we used MSI Afterburner, and to ensure we achieved the highest rating possible the GPU voltage was unlocked. This allows us to scale the core voltage up to 1350mV, which resulted in a 1260MHz overclock. At this speed the core is running 20.6% faster than the reference clock speed, which is quite good considering the default GPU clock is already set at 1GHz. When it came to the memory we were able to turn the dial up by 160MHz, which is an increase just shy of 13%. That translates into the memory running at 1285MHz (5140MHz effective), increasing the total memory bandwidth to 82.2GB/s.
Since the HD 7750 was not able to utilize the over-voltage function, it didn't fair quite as well as the HD 7770. The HD 7750 was only able to net an additional 90MHz over the reference 800MHz clock in our labs. This gave us an increase of just over 10%, which isn't going to produce results that are drastically different from the reference clock speeds. The memory also capped out right around 10%, meaning we were able to increase the frequency of the GDDR5 memory up to 1271MHz. In comparison to the reference memory clock that is an increase of 146MHz, which increases the bandwidth to 81.3GB/s.
||AMD Radeon HD 7970||AMD Radeon HD 7950||AMD Radeon HD 7770||AMD Radeon HD 7750||AMD Radeon HD 6970|
||3GB GDDR5||3GB GDDR5||1GB GDDR5||1GB GDDR5||2GB GDDR5|
||Nvidia GTX 460||Nvidia GTX 470||Nvidia GTX 480||Nvidia GTX 570||Nvidia GTX 580|
||1GB GDDR5||1.25GB GDDR5||1.5GB GDDR5||1.25GB GDDR5||1.5GB GDDR5|
Futuremark's latest 3DMark 2011 is designed for testing DirectX 11 hardware running on Windows 7 and Windows Vista. The benchmark includes six all new benchmark tests that make extensive use of all the new DirectX 11 features including tessellation, compute shaders and multi-threading.
The results of the HD 7770 were quite good in 3DMark 11, as it nearly matched the HD 6850 at the default clock speed and easily outperformed it once we got the clock speed up to 1260MHz. The HD 7750 didn't fair quite as well, as it was not able to surpass the previous generation HD 6770 even after we overclocked the core to 890MHz.
To better understand the results, lets break them down into percentages and compare the cards to their competition. Looking at the HD 7770, we can see the performance at the default speed is roughly 5% slower than the HD 6850, 6% faster than the HD 6790 and 17% faster than the HD 6770 is actually replaces. Overclocking of course improved the results, as the increase from the stock frequencies to our custom clocks maxed out at 15%.
In comparison, the HD 7750 was 6% slower than the HD 6770, and 17% slower than the HD 6790. While these results aren't overly impressive, they should give the HD 7750 a performance increase of around 10% compared to the HD 6750.
Unigine Heaven became very popular very fast, because it was one of the first major DirectX 11 benchmarks. It makes great use of tessellation to create a visually stunning heaven.
The results in Unigine came out similar to what we observed during our Futuremark benchmark; the results of the HD 7770 were remarkably similar to the HD 6790 at the default clock speeds, and slightly better than the HD 6850 once overclocked. Meanwhile the performance of the HD 7750 was nearly spot on with the HD 6770.
Since the HD 7750 essentially tied with the HD 6770, we are going to skip the percentage difference for that model because it appears as if it is going to fill the performance spot of the HD 6770, but with better power efficiency. The same can be said for the HD 7770, as the results thus far show it pushing a similar amount of pixels as the HD 6790 at the stock level, and slightly outpacing the HD 6850 once overclocked.
Aliens vs Predator is a DX11 Benchmark that runs though a scene straight out of the classic 80’s movie, Aliens. Since it uses DX11, it can often be more than a graphics card can handle.
Aliens vs Predator showcases the trend seen in the previous benchmarks. Looking at the HD 7770, it is right on par with the HD 6790 at the stock 1GHz speed, and slightly faster than the HD 6850 once overclocked. However, since the HD 7770 has a smaller 128-bit memory interface, it is going to be hard for it to compete with the HD 6850 at 2560x1600 or higher simply because the bandwidth isn't there.
On the other side of the coin, the HD 7750 didn't manage to impress at all in this benchmark. On average it was 25% slower than the HD 6770. Our first reaction was that this was a driver issue, but since the HD 7770 scored relatively well, the issue must lie with the hardware and not the software.
Batman: Arkham City is the sequel to the smash hit, Batman: Arkham Asylum. The game was created with the Unreal 3 Engine, and includes areas with extreme tessellation, high res textures and dynamic lighting. Batman, also includes native support for PhysX and is also optimized for Nvidia 3DVision technology.
Both of the graphics card did well for their respective price points. Comparing the HD 7770 to the cards around it, it came out 4% faster than the HD 6790 and 10% slower than the HD 6850. As with most of the prior tests, the HD 7750 really only competes with the HD 6770.
Battlefield 3 is designed to deliver unmatched visual quality by including large scale environments, massive destruction and dynamic shadows. Additionally, BF 3 also includes character animation via ANT technology, which is also being utilized in the EA Sports franchise. All of this is definitely going to push any system its threshold, and is the reason so many gamers around the world are currently asking if their current system is up to the task.
Unlike the other games we benchmark, the performance of Battlefield 3 is tested during online game play. We ensure our results are accurate by running through each resolution four times before averaging the results.
Interestingly, the results in one of the most demanding games currently on the market showed the HD 7770 and HD 7750 performing slightly better than they have prior to this point.
The HD 7770 performed better than the HD 6790 by 14%, and was actually dead on with the HD 6850 in most resolutions. Additionally, the HD 7770 at 1260MHz was able to compete aggressively with the both the HD 6870 and GTX 560, something we have not been seeing up to this point.
The HD 6750 however was still roughly in the same ball park as the HD 6770, but it did manage to beat it in two out of thee three resolutions once overclocked.
Crysis 2 is a first-person shooter developed by Crytek and is built on the CryEngine 3 engine. While the game was lacking in graphical fidelity upon its release, Crytek has since added feature such as D11 and high quality textures. This improved the in-game visuals substantially, which in turn pushes even high-end hardware to the max.
We can only assume a driver issue is at work/fault here, because the performance is Crysis 2 was just not where it should have been for either of the new cards.
DiRT 3 is the third installment in the DiRT series and like it's predecessor incorporates DX11 features such as tessellation, accelerated high definition ambient occlusion and Full Floating point high dynamic range lighting. This makes it a perfect game to test the latest DX11 hardware.
One thing we can say is other than the few oddballs (I'm talking about Crysis 2), the performance of both cards remained consistent across the board. Basically this means the HD 6750 is on par with the HD 6670, while the HD 7770 is more or less equal to the HD 6790 and once overclocked it is roughly equal to the HD 6850. From these results we can see that the performance of the Cape Verde graphics cards is not earth shattering, but rather just a shift from the previous generation.
Metro 2033 puts you right in the middle of post apocalyptic Moscow, battling Mutants, rivals and ratio-active fallout. The game is very graphics intensive and utilizes DX11 technology, making it a good measure of how the latest generation of graphics cards perform under the latest standard.
The results in Metro 2033 demonstrate the power of the Southern Islands' 9th generation tessellator, as both cards managed to do quite well considering they both run on a 128-bit memory interface. However, since this game runs best on graphics cards with high memory bandwidth, it is going to be hard for the Cape Verde cards to compete with graphics cards that have a 256-bit memory interface.
Total War: Shogun 2 is a game that creates a unique game-play experience by combining both real-time and turn-based strategy. The game is set in 16th-century feudal Japan and gives the player control of a warlord battling various rival factions. Total War: Shogun 2 is the first in the series to feature DX11 technologies to enhance the look of the game, but with massive on-screen battles it can stress even the highest-end graphics cards.
The cards complete our gauntlet of benchmarks essentially the same place where the started. In this last benchmark, the HD 7770 was slightly faster than the HD 6970 when running at 1GHz, and slightly faster than the HD 6850 at 1260MHz. Similarly, the HD 7750's results were close to the HD 6770, although the stock performance was again lower than what we would have liked to see.
To measure core GPU temperatures, we run three in-game benchmarks and record the idle and load temperature according to the min and max temperature readings recorded by MSI Afterburner. The games we test are Crysis 2, Lost Planet 2 and Metro 2033. We run these benchmarks for 15 minutes each. This way we can give the included thermal solution and GPU time to reach equilibrium.
From a thermal standpoint both of the Cape Verde graphics cards were solid. They both displayed excellent thermal results and were extremely quiet across the board. The only time we noticed much fan noise at all was when we manually set the HD 7770 fan speed above 50% so that we could comfortably increase the voltage level.
To measure power usage, a Kill A Watt P4400 power meter was used. Note that the numbers represent the power drain for the entire benchmarking system, not just the video cards themselves. For the 'idle' readings we measured the power drain from the desktop, with no applications running; for the 'load' situation, we took the sustained peak power drain readings after running the system through the same in-game benchmarks we used for the temperature testing. This way we are recording real-world power usage, as opposed to pushing a product to it's thermal threshold.
Both the HD 7750 and HD 7770 really delivered when it came to performance-per-watt. At the default settings, the idle and load power rating was a sparse 99W and 161W for the HD 7750. As for the HD 7770 it managed to run at a low 106W during idle and 212W under full load. So, what both cards lack in overall performance they make up for in sheer power efficiency. However, after we over-voltage the HD 7770 the power consumption increased substantially.
Since Cape Verde marked the first true update to the Juniper series in two generations, we had high hopes for these new 123mm² graphics processors. However, the performance just never materialized as our results showed both Cape Verde based graphics cards didn’t necessarily bring anything new to the $109 through $159 market segments in terms of performance. Instead what we got was a slight shifting around, where the HD 7770 essentially replaces the HD 6790 in terms of performance, and the HD 7750 takes the performance spot of the HD 6770.
What the HD 77xx series does do right though is delivering a robust feature-set that includes support for Eyefinity 2.0, HD3D technology, ZeroCore Power, DirectX 11.1 and App Acceleration. All of these, along with the performance, make both the HD 7770 and HD 7750 well-rounded graphics cards can produce over 30FPS in DX11 games at the higher resolution settings. Additionally, the performance-per-watt has been significantly improved over the previous generation, as the HD 7770 is able to run with a clock speed of 1GHz and still consume less power than the stock HD 6790, while the HD 7750 has a max power rating of only 55 watts.
Overclocking was also able to improve things on the performance front, at least when it came to the HD 7770. In our labs we were able to turn up the knob on the 1GHz core to 1260MHz, which is an increase of just over 20%. At this speed, the HD 7770 netted on average an additional 15% performance boost, which allowed it to perfom better than the HD 6850, and at times nip at the heels of the HD 6870. We were pleased with these results, as it allows the HD 7770 to offer the same performance as a graphics card with a slightly higher MSRP. The HD 7750 on the other hand was only able to overclock by 10%, which didn’t deliver much of an impact on the performance.
The Cape Verde graphics cards are both well-rounded products that offer better performance-per-watt and performance-per-millimeter, as well as improved thermals and acoustics, than the previous generation. However, if you were expecting the HD 7770 and HD 7750 to effectively perform equal to the HD 6870 and HD 6850, know that Cape Verde just doesn't quite get there.
Most Cape Verde based graphics cards will not come with the default clock speeds though, as most HD aftermarket HD 7770s will come with a GPU clock speed of around 1.1GHz. So, most models on the market will have better overall performance than the AMD reference models displayed in this article.
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