AMD Radeon HD 7870 & 7850 Launch Review

Author: Chris Ledenican
Editor: Howard Ha
Publish Date: Saturday, March 3rd, 2012
Originally Published on Neoseeker (http://www.neoseeker.com)
Article Link: http://www.neoseeker.com/Articles/Hardware/Roundups/AMD_HD_7870_7850/
Copyright Neo Era Media, Inc. - please do not redistribute or use for commercial purposes.

The Southern Islands family consists of three 28nm GPUs: Tahiti, Pitcairn and Cape Verde. Of the three, we have examined the high-end Tahiti GPU and mainstream Cape Verde, leaving only Pitcairn untested. In today’s review we are able to round out the series as Pitcairn has finally arrived in our labs, allowing us to benchmark, dissect and analyze AMD’s latest Graphics Core Next (GCN) core.

In total we are going to be examining two new cards, AMD's Radeon HD 7870 and 7850, both based on the GCN architecture. GCN is revolutionary in that eliminates the previous VLIW design for a non-VLIW SIMD engine. Additionally, the “Pitcairn” cores pack in between 16 and 20 GCN cores, 32 raster units and 128 texture units, all while boasting a transistor count of 1.4 billion in a 212mm² die. These specifications place these new products right in the middle of the Southern Islands family, and give them a good shot a competing with last gen's high-end hardware.

Along with the internal specifications, Pitcairn shares the same feature set as the HD 7900 series. This gives both models support for Eyefinity 2.0, App Acceleration, DX 11.1 and HD3D technology. What is different, however, is that the 7800 series runs on a 256-bit interface instead of the 384-bit interface utilized by the HD 7900 series. With the slightly scaled back architecture and memory interface, the HD 7800 series is able to launch at a lower price than the high-end gear, while still having the ability to render massive amounts of pixels-per-second.

If you remember anything about the Radeon HD 7970 launch, then you've probably figured our "review" today is more of an in-depth, hands-on preview of the new graphics cards, as the hardware won’t be in the channel until later this March 19th. AMD has timed the preview launch to happen just before events such as CeBIT and GDC to avoid any possible leaks.

Pitcairn leverages the same GCN architecture as the Cap Verde and Tahiti based graphics cards. This means the 7800 series has the same feature set and internal design as the 7900 and 7700 series, but naturally with different specifications. With that in mind, lets recap the new architecture and look at where the Pitcairn XT and Pro fit.

AMD's Graphics Core Next is a scalable architecture designed to be optimized for both graphics horsepower and compute power. The HD 7800 series brings two new GPUs to the market, "Pitcairn XT" and Pitcairn Pro", which are compiled of 20 and 16 Compute Units, respectively. By comparison, the HD 7970 has 32 compute units, each having 64 streaming processors. This gives the HD 7970 a grand total of  2048 streaming processors. Looking at the HD 7800 series, the HD 7870 packs in more than half of the amount of CUs, which at 20 gives the card a total of 1280 SPs, The HD 7850 meanwhile has exactly half the compute units as the HD 7970, sixteen, which gives this model a total of 1024 streaming processors.

In addition to the compute units, the HD 7800 series includes dual Geometry engines, 8 Render Back-Ends, 768KBs of read/write L2 cache, and a 256-bit memory bus all running on a PCI Express 3.0 x16 bus interface and packing in a total 2.8 billion transistors. Like the HD 6900 series, the dual geometry engines each have their own Rasterizer and Render Back-End units, but share the Compute Units. You can basically think of these Geometry engines as having dual cores inside the GPU.

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 runs independently and asynchronously to the primary graphics pipeline. This allows the GPU to process an intensive compute simultaneously with the graphics pipeline as it is running an intensive 3D application, and maximizes the utilization of the available compute power. Paired with this is the processing core and dual DMA engines which allow the HD 7800 series to saturate the Gen 3.0 PCI-Express interface with a Teraflop of bidirectional double precision.

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 7970 has a total of 32, giving it up to 2TB/s of bandwidth. As mentioned before, each L1 cache has both read and writes functions, something new to the Southern Islands architecture. Each L1 still has a L2 cache to fall back on, but the L2 also now includes both read and write functions. The HD 7870 and 7850 come packed with 8 L2 caches that feed back into the L1 cache which are also 64 bytes per clock. This gives the HD 7870 and HD 7850 a total of 153.6GB/s of bandwidth, with the default GPU clock speed for both reads and writes.

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 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 does 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. Essentially the textures that are not going to be displayed are not immediately 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 for the lower resolution 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.

This new feature gives the HD 7800 series 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 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 same 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, 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.

We can really see the Southern Islands family resemblance in the HD 7800 series. Both models share the same red and black color scheme and uses a similar rear mounted blower style fan as their older siblings. Along with the aesthetics, the HD 7800 cards also use the same rounded design of the back end of the shroud, designed to improve ventilation when the cards are being used in CrossFireX configurations. As far as the dimensions go, both the HD 7870 and HD 7850 are 9.5" in length, which means they should fit into most cases on the market.

The "Pitcairn" GPU is the third iteration in the Southern Island series, and is designed to offer better performance-per-dollar than its higher-end counterparts. Examining the core internally, Pitcairn has a total of 2.8 billion transistors and like the other cards in the series is built on a  28nm node. The die size however is different; at just 212mm², Pitcairn is over half the size of the Tahiti GPU and smaller than the 255mm² Barts GPU.

Let’s start with the HD 7870. Internally this card is based on the Pitcairn XT design which sports 20 compute units, 1280 streaming processors, 32 ROPS and 80 texture units. The default GPU clock speed is set at 1000MHz, which makes this the second graphics card released from AMD to have a default clock speed of 1GHz. At this speed, the GPU has a pixel fillrate of 32GPixel/s, a texture fillrate of 80GTexel/s and compute performance at 2.65TFLOPs. Additionally, the HD 7870 runs on a 256-bit memory interface and has a 2GB GDDR5 frame buffer set at 1200MHz (4.8Gbps effective).

Like its older sibling, the HD 7850 is based on the GCN design, but it uses the slightly scaled back specifications of the Pitcairn Pro GPU. This gives the HD 7850 a total of 16 compute units instead of 20, which makes for 1024 streaming processors. The rest of the specifications include 32 ROPs, 64 texture units and a GPU engine clock that is set at 860MHz, giving it a compute performance of 1.76TFLOPS. Turning to the memory, the HD 7850 has the same interface, 2GB frame buffer and clocks speeds, making it identical down to the total memory bandwidth.

Attached to the PCB of both cards is a single CrossFireX connector and a PCIe Generation 3.0 x16 lane.  By using the PCIe 3.0 interface, the board 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. We are a bit disappointed to see the HD 7800 series only supports 2-way CrossFire support, but this tends to be the preferred configuration for most CrossFire users. It would have been amazing to see exactly what three or four of these cards would be capable of though!

Since the HD 7870 and HD 7850 have the same feature-set as other cards in the Southern Island family, they are equipped with PowerTune technology. To recap, PowerTune is basically a power management system that maximizes the performance of the board via dynamic power adjustment. It does this by increasing the GPU clock speed in real time when the GPU detects power headroom, and throttling the clocks when a certain power limit is exceeded. This allows the board to adjust the clock speeds on a microsecond level.

Breaking it down by board, the HD 7870 has a typical board power rating of 175W, while the HD 7850 has a rating of only 130W. Considering these cards could potentially perform at the same level as last generation's high-end hardware, the power ratings for both boards is extremely good. This is in keeping with the better performance-per-watt we have been seeing from the 28nm node, but it should also give both cards the ability to scale beyond 1GHz.

The HD 7870 and HD 7850 also support "Zero Core Power". Traditionally, anyone using multiple GPUs in a single system had to deal with a high power idle state, simply because each card was still actively drawing system power; each graphics card could produce 30+ watts of power even when the system wasn't under load. With "Zero Core Power", the extra graphics cards in a CrossFireX system are disabled, shutting down the fans and capping any voltage from going to the core. Since PowerTune works on a microsecond level, "Zero Core Power" will not interfere with gaming as all the GPUs can become active again in just microseconds.

The video outputs are consistent with the rest of the series. In total there are two Mini-DP connectors, a single HDMI 1.4a connector and a Dual-Link DVI connector. Both cards also uses the same non-stacked DVI design as the HD 7970, which improves both the acoustics and exhaust rate giving airflow a clearer path to travel out of the heatsink. Like many other recent AMD cards, the HD 7800 series comes 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.

All the outputs include the same design and features as those found on the HD 7900 series. This gives the Pitcairn cards' DP 1.2 ports the ability 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 is going to make viewing images and playing games smoother across the board. The HDMI and DP ports can also be paired together (with a HDMI to DVI adapter) to support HD3D Surround.

The thermal solution used to cool the HD 7800 series has been scaled back a bit in comparison to the higher-end gear. Instead of using a large multi-step vapor chamber heatsink, AMD has stayed with the tried and true heatpipe heatsink design. Considering the size and power consumption rating of the Pitcairn GPU, most any modern heatsink should be more than adequate, as evidenced in how the HD 7800 cards feature the same heatsink used on the older HD 6800 series.

Starting at the base of the heatsink, there are four thermal pads that cover the eight on-board memory modules and a large opening for the actual heatsink. Other than these areas, the base of the heatsink is mostly designed to secure the thermal solution to the graphics card and ensure the weight is evenly distributed.

The actual heatsink used with the cards consists of a small aluminum array that is attached to three separate heatpipes. Each heatpipe is copper and extends from the core throughout a section of the array. This maximizes the heat transfer, by allowing the three pipes to spread out the heat uniformly, thus making it easy for the airflow to push it out of the array. The base of the heatsink is also solid copper, which is one of the best materials for transferring heat. The heatsink is small, but it should be more than efficient to cool the core, especially when we factor in the low thermal load of the Pitcairn GPU.

Directly behind the heatsink is the blower style fan. The position of the fan allows the air to flow directly though the heatsink. This trajectory ensures the hot air being absorbed into the array is constantly moving, preventing any area from getting excessively hot. The dissipation rate is directly tied to the temperature of the core, so the less efficient a fan, the hotter the cores will be. In the configuration AMD has set up, the fan should efficiently dissipate the heat even at low RPM.

The blower style fan on the HD 6800 series utilizes optimized fan blade technology, giving the fan a larger and wider blades. This design allows it to push higher CFM with a lower decibel rating than the fans used on the HD 6000 series. The specs for the fan show it runs at 1.7A @ 12V DC and has a 2 ball bearing design, but unfortunately we don't have the exact CFM or dBA rating for the fan.

Both the HD 7870 and HD 7850 are built on the same PCB, but there is a difference in the amount of power connectors, capacitors and chokes. Both cards include a CHL8228G voltage controller from the CHiL semiconductor corporation. The CHL8228G is a dual-loop digital multi-phase controller that can drive up to 8 phase units, and features Input Voltage Management to allow up to 3 input voltages to be monitored. This will ensure the card is adequately powered, and improves the overall power efficiency.

The board also has a front mounted VRM. With the VRM moved from the back to the front the heat coming off the power circuitry is not going to pass through the heatsink, which allows the heat from the VRM to be exhausted without interacting with the GPU.

(HD 7870)

(HD 7850)

Overclocking:

Graphics cards built on a 28nm node require less power, which in turn allows the clocks to be cranked up without dangerously exceeding the TDP or thermal threshold. In our testing of the other Southern Islands graphics cards, each has been able to easily scale above 1GHz and 1200MHz or beyond when additional voltage is available.

Overclocking the two graphics cards was a slightly different experience in each case due to the fact that Afterburner unlocked the voltage for the HD 7870, but not the HD 7850. This allowed us to push the HD 7870 higher than the HD 7850, but both actually produced good results.

In our labs the HD 7870 was able to scale to 1250MHz when the voltage was increased to 1299mV. That is an increase of just over 205MHz, which is impressive considering the default clock speed is already set at 1GHz. While the GPU scaled well, the memory on the HD 7870 had some issues. In most tests, the memory was able to increase to 1450MHz, but then some benchmarks would crash, leading to major issues with screen freezes and palatalization across the desktop. For this reason, the highest we could get the memory was 1326MHz while still remaining stable, which is an increase nearly 10 percent.

The HD 7850 didn't have the voltage control options available, but we were still able to hit the maximum allotted frequencies. This card was able to overclock to 1050MHz with no additional voltage, which is an increase of 18.1%. Additionally, the HD 7850 didn't have the same memory issues as the HD 7850, so we easily scaled the memory frequency up to 1450MHz (5800MHz effective)

Hardware Configuration:

Drivers:

Benchmarks DX11:

Test Settings:

Usage:

Specifications:

(Note: All models might not be included in this review. The table below is to be used for comparison purposes)
AMD Specifications
Model
AMD Radeon HD 7970 AMD Radeon HD 7950 AMD Radeon HD 7870
AMD Radeon HD 7850
AMD Radeon HD 6970
Processing Cores
2048 1792 1280 1024 1536
Core Clock
925MHz 850MHz 1000MHz 860MHz 880MHz
Memory Clock
1375MHz 1250MHz 1200MHz 12000MHz 1375MHz
Memory Interface
384-bit 384-bit 256-bit 256-bit 256-bit
Memory Type
3GB GDDR5 3GB GDDR5 2GB GDDR5 2GB GDDR5 2GB GDDR5
Fabrication Process
28nm 28nm 28nm 28nm 40nm
NVIDIA Specifications
Model
Nvidia GTX 460 Nvidia GTX 470 Nvidia GTX 480 Nvidia GTX 570 Nvidia GTX 580
Processing Cores
336 448 480 480 512
Core Clock
675MHz 607MHz 700MHz 742MHz 782MHz
Memory Clock
1100MHz 837MHz 924MHz 1250MHz 1002MHz
Memory Interface
256-bit 128-bit 320-bit 320-bit 384-bit
Memory Type
1GB GDDR5 1.25GB GDDR5 1.5GB GDDR5 1.25GB GDDR5 1.5GB GDDR5
Fabrication Process
40nm 40nm 40nm 40nm 40nm

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.

We are going to break things down in terms of percentages, and compare each card to its closest competitors.  On average, the performance of the HD 7870 was around 5% slower than the HD 7950 and 9% slower than the GTX580, but 7% faster than the HD 6970 and 14% faster than the HD 6950. The HD 6850 on the other hand came out 9% faster than the GTX 560 Ti, 14% faster than the HD 7870 and just 3% slower than the HD 6950.

Overclocking managed to improve the performance of the HD 7870 by as much as 17%, while the HD 7850 peaked at 18% faster when testing at 2560x1600.

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 stock results were very good for both cards, as the HD 7850 essentially tied with the HD 6970 while the HD 7870 was faster than the GTX 570. In this benchmark, the HD 7870 was nearly 4% faster than the GTX 570, and 8% faster than the HD 6970. Comparing the HD 7870 to the GTX 580 and HD 7950 wasn't so cut and dry though, because the memory interface is larger on both the other cards. For this reason, the HD 7870 was 6 % slower than the GTX 580 at 1680x1050 and 1920x1080, but a whopping 23% slower once it hits 2560x1600. The same was true for the HD 7950, as the HD 7870 was around 15% slower at 1080P, but 23% slower at 2560x1600.

The HD 7850 performed good as well. In our labs, this $250 graphics card was nearly 6% faster than the HD 6950, 12% faster than the GTX 560 Ti, 18 faster than the HD 6870 and 3% slower than the HD 6970. Not too bad considering the price of the graphics card, and the fact that overclocking the GPU beyond 1GHz can net an additional 10% performance boost.

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.

Moving beyond synthetic benchmarks, we can finally see how the HD 7870 and HD 7850 perform in more practical tests, such as gaming!

The HD 7870 was on average 13% faster than the GTX 570 in AvP, nearly 2% faster than the HD 6970 and 5% slower than the GTX 580. Turning to the HD 7850, it was 8% faster than the HD 6870, 7.5% faster than the GTX 560 Ti and 7% slower than the HD 6950.

Overclocking increased the performance of the HD 7850 GHz and HD 7850 by 11% and 13%, respectively.

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.

The HD 7870 performed at the same level as the GTX 570 and HD 6970, while being around 13% slower than the GTX 580. This could be due to driver support, or the game simply being optimized for NVIDIA hardware in the first place, but the results were just not as good as what we saw in Aliens vs Predator. The HD 7850 had results similar to the HD 7870, but it managed to do slightly better against its closet rivals.

In total the HD 7850 was head-to-head with the HD 6950, 13% faster than the HD 6870 and 18% faster than the GTX 560 Ti.

Battlefield 3 is designed to deliver unmatched visual quality by including large scale environments, massive destruction, 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.

The HD 7870 GHz was able to perform at the same level as the HD 7950, and what that tells us is it is time to break all of our graphics cards and retest this game with the latest drivers. Looking at the cards where the performance should be right on even with slightly older drivers, we can see the HD 7870 is roughly 14% faster than the HD 6970 and between 5% and 16% faster than the GTX 570, depending on the resolution.

The HD 7850 also did well in this benchmark, but again it was on a per resolution basis. Looking at the performance between the HD 7850 and the HD 6950, we can see the HD 6950 was faster at the lower resolutions, but the HD 7850 pulled ahead at 2560x1600. The same was true for the GTX 560 Ti, but the difference was more dramatic between these two cards.

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.

The performance of the HD 7850 here was better than that of the HD 6950 by 2%, and 12% better than the HD 6870. Comparing against the NVIDIA solutions was hard though, as the HD 7850 was faster than both the GTX 570 and GTX 560 Ti at the highest resolutions, but the NVIDIA cards seemed to have an easier time up to 1080P. The HD 7870 however was 12% faster than the HD 6970 and 13% faster than the GTX 570.

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.

The HD 7950 again fell slightly behind the GTX 580, but continues to display performance beyond the capabilities of the HD 6970. The 7870 GHz meanwhile was between 5% and 9% faster than the HD 6970. The HD 7850 continues to be slightly slower than the HD 6950 it is replacing.

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.

Metro 2033 loves memory bandwidth, and with their 2GB frame buffer on a 256-bit interface, both the HD 7870 and HD 7850 performed at levels not usually seen in graphics cards at this price range.

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.

During our Total War benchmarking, the results were mostly consistent with what we have been seeing throughout the testing process. Looking at the HD7850, it is simply just not as fast as the HD 6950. This would have been fine if it was the replacement for the HD 6850 but since its not, the price tag might be an issue with some gamers. The HD 7870 was able to surpass the HD 6970 due in no small part to the 1000MHz clock speed.

Temperature:

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.

During our testing, the HD 7800 series proved to be one of AMD's most efficient to-date. At the default settings, the temperature of the HD 7870 only reached 71°C, while the HD 7850 never passed 56°C. This put the higher end HD 7870 and HD 7850 below even mid-range graphics cards such as the HD 6850. Since the GPU was able to remain nice and cool during our testing, the fan RPM level stayed consistently low even though we were benchmarking a card using the reference thermal solution, so both cards were quiet even during long gaming sessions.

Power Consumption:

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.

When it came to performance-per-watt, both the HD 7800 series cards performed brilliantly. At the default settings, the idle and load consumption ratings were a sparse 91W and 101W, respectively. This made it more efficient than any cards in this range we have tested to date. The load power state was also very good as well, as even when overclocked, both cards still remained well under 300W. So, even while the HD 7870 GHz and HD 7850 are not dramatically more powerful than the cards they are replacing they offer substantially better performance-per-watt

The metric we tend to use for gauging the performance of new mid-range graphics cards is its ability to meet or exceed the performance of the previous generation’s higher-end models. In this regard the HD 7800 series does a phenomenal job, as the HD 7870 and HD 7850 were not only able to keep pace with the HD 6970 and HD 6950, respectively, but they also bested them in terms of performance-per-watt and overclocking potential. So, overall the HD 7870 and HD 7850 are both better graphics cards than the current gen models they are replacing.

Both the HD 7870 and HD 7850 also have the same robust feature set as the HD 7900 series. With this level of support, both cards come packed with native support for features such as HD3D, Eyefinity 2.0, DX 11.1, App Acceleration, and ZeroCore Power technology. The HD 7870 and HD 7850 not only perform at essentially the same level as the 6900 series cards they are replacing, but also have better feature-sets to boot. This should give you a good perspective on exactly where the cards stand in terms of performance and features, but pricing is also a huge metric we have to factor in.

AMD made clear that the HD 7800 graphics cards are not the replacement to the 6800 series, but rather they should be considered the replacement for the HD 6900 series. Obviously this isn’t due to the performance, because both the HD 7870 and HD 7850 are extremely similar to the HD 6900 cards they are replacing. The real reason is the pricing structure.

At time of launch, the HD 7870 GHz Edition and HD 7850 will have an MSRP of $349 USD and $249 USD, respectively, which is exactly the same as the current retail pricing of their 6900 series counterparts. So, offering them as the replacement to previous generation's high-end hardware gives AMD the ability to keep the prices higher than if they were the direct replacement to the HD 6800 series.

However, since both Pitcairn graphics processors are built on a 28nm node they can overclock through the ceiling, allowing the chips to yield performance higher than what was possible with the HD 6900 series. In our labs, we were able to get the HD 7870 to 1250MHz and the HD 7850 to 1050MHz. At these speeds, both the chips increased in performance by up to 20%, allowing them to compete with graphics cards well beyond their price range.

While we would have liked to see the price of the HD 7870 and HD 7850 fall somewhere in between the HD 6800 and HD 6900 series, both models are still great cards that excel when it comes to performance-per-watt and overclocking. These alone make them better options than the current gen models they are replacing, but add to this a robust feature set, phenomenal thermal performance and quiet acoustics, and the HD 7800 series becomes a damn good option for any high-end gamer.

»Neoseeker.com

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