iXBT Labs - Computer Hardware in Detail






AMD 785G Chipset with Integrated Graphics for the Socket AM2+/AM3 Platform

Supporting Hardware-Assisted HD Video Transcoding and DirectX 10.1

The AMD 780G chipset, launched over a year ago, was actually the first successful attempt to equip motherboards with a sterling graphics processor. Low-End graphics cards actually offered similar 3D performance, and the UVD allowed to decode HD Video, even if the computer was built with a Sempron, while more powerful processors were offloaded for other tasks. Note the support for all video outputs, including DVI, HDMI, Display Port, and the integrated audio codec to output audio to an HDMI receiver.

AMD used the bleeding edge 55-nm fabrication process (at that time) to obtain such GPU speed. As a result, users got an unexpected opportunity to overclock the graphics core integrated into the chipset. It was often possible to double the GPU frequency.

Later on there appeared a faster modification of this chipset called AMD 790GX, which is still a leader in 3D performance among integrated solutions. It must be noted that both chipsets for the AMD platform together with Phenom/Athlon processors played the locomotive role for the budget and Mid-End segments. That is users really chose the AMD platform that offered attractive motherboards. Besides, the Intel platform with similar functionality would have been much more expensive.

With the rollout of Phenom II and Athlon II processors, popularity of motherboards for the AMD platform has grown due to the attractive processors, which fare well against competing products. But it never hurts to fortify one's position. Besides, from the purely technical point of view, the graphics department in AMD had ready projects that should be adapted to integrated solutions at least for unification reasons. And as is well known, motherboard manufacturers do not like to launch new models with the relatively old chipsets, as new sockets are introduced. As DDR3 memory is getting cheaper, there grows demand for Socket AM3 motherboards with integrated graphics – Mid-End models, if not the cheapest solutions. As a result, there has appeared an overhauled version of the 780G with the index incremented only by five.

The flowchart shows that it's absolutely identical to the AMD 780G in its interfaces and peripheral features. AMD officially allows manufacturers to choose any Southbridge, so they can install either the SB700 that was used with the 780G or the SB710 (probably the most natural choice that features Advanced Clock Calibration support) and SB750 (for top motherboards: it adds RAID 5 support to the SB710 functionality). The main difference lies in the graphics core.

Unlike the HD 3200, the new graphics core HD 4200 supports DirectX 10.1 and hardware transcoding (converting video from one format into another, including main HD Video formats H.264 and VC1, and scaling video for portable players and online video). Besides, the new graphics core contains a state-of-the-art modification of the video decoder (UVD), which should improve its performance and image quality, including smoother scaling of low-res video for large displays. It required some extra transistors on top of the previous 205 millions (they do not disclose how many exactly), but apparently not very many, especially as the other units must have been optimized to free some of the transistors.

As a result, it was decided to keep the 55-nm fabrication process for this chipset. It may seem unexpected, considering that modern graphics processors for discrete graphics cards from AMD are being actively upgraded from the 45-nm to 40-nm fabrication process already. To all appearances, that's economic reasons in action: the contracted chip manufacturer TSMC wants to prolong service life of its 55-nm production lines (the crisis reduced the load on these production lines, so they did not work out their designed service life) and drops prices for its products. Upgrades to thinner fabrication processes are primarily initiated to cut down production costs. It happens because thinner fabrication processes mean smaller die surfaces, and thus more chips from each silicon wafer. But it's not the sole factor that affects pricing in real conditions.

As frequencies remain on the same level as well as the number of shader processors, we can expect performance gains only in those tasks that use the new features of this chipset. That is: video encoding/decoding, as well as in some games that use DirectX 10.1 features (improvements in this version have to do with optimizations rather than with better special effects – that is performance gains due to more effective shader code). Nevertheless, this chipset claims to have lower power consumption, even though indirectly: owing to a more flexible PowerPlay mode that controls GPU frequency and switches off idle units.

Just like the 780G, the chipset allows to install a local video buffer (up to 128 MB of DDR2 or GDDR3 memory). This feature promises to be more popular among motherboard manufacturers than in case of the 780G (but less frequent than in motherboards with the 790GX). But Hybrid CrossFire mode is not mentioned in the specifications at all. From the practical point of view, it would have been strange to keep the same list of graphics cards to work with the 780G, and people would hardly use this opportunity in practice. So this mode will most likely return only after the next family of chipsets (Series 800). However, owners of powerful graphics cards, who may want to install them into a motherboard with the 785G chipset, will probably enjoy another new feature that can be enabled in updated drivers. To all appearances, Hybrid Graphics mode, which has been used in notebooks for a long time already (designed by NVIDIA for the nForce 780a chipset) is almost ready for the desktop platform based on the chipset and graphics cards from AMD. Gigabyte engineers already leaked a word about this feature, but users will have to wait a little more.

We only wish that this implementation is more convenient than what NVIDIA offered and switches automatically from a discrete graphics card to the integrated core when you quit a game and vice versa. There is another cosmetic addition: the integrated audio codec can now output 7.1-channel audio through HDMI (it used to support only stereo and 5.1-ch formats). It's hardly interesting for a Low-End integrated solution, which is usually plugged to a TV set with stereo speakers. However, it's an expectable and logical addition, because this mode is formally supported by competing chipsets (without integrated audio codecs, that is capable of outputting audio only from the on-board audio chip).

By the time this chipset was announced, practically all manufacturers were getting ready to launch such motherboards. We shall certainly test the most interesting models, when we get them in our lab. As for now, we'll get acquainted with the chipset by the example of Gigabyte MA785GT-UD3H, which did not even make it to the official slide. That is considering the six motherboards from Gigabyte mentioned on the slide and its active usage of previous chipsets, we can conclude that Gigabyte apparently likes to design motherboards based on integrated chipsets from AMD. And it probably wants to repeat the success of such hits as the MA78GM-DS2H and MA790GP-DS4H.

Performance tests

Testbed configuration:

  • Motherboards:
  • Processors: AMD Athlon II X2 250 and Intel Core 2 Duo E7400
  • Memory: 4 GB DDR2-1066 Corsair CM2x2048-8500C5D (DDR2-1066, 5-5-5-15-2T)
  • HDD: Seagate Barracuda 7200.10 (SATA-II, 7200 rpm)
  • Power supply unit: AcBel ATX-550CA-AB8FB


  • OS and drivers:
    • Windows Vista Ultimate SP1 x64
    • ATI Catalyst 9.8beta
    • Intel G45 Express Chipset + INF Update
  • Test applications:

Test results

Judging by technical characteristics, performance difference from the 780G may appear only in those applications that use the new features. So first of all we were interested how much the 785G could accelerate transcoding.

You can read about hardware-assisted video decoding in Cyberlink PowerDirect here. But now we'll use a simpler utility (MediaShow Espresso) from the same developer. This program does not have video editing functions, and it's written for non-professional transcoding tasks. It has a simple interface, and novice users can choose ready profiles for their needs, be it converting video for iPod, PlayStation 3, or YouTube.

This very program is considered to use ATI Stream features in the best way. Subjectively, it agrees with prospects of using GPU resources for serious encoding tasks and many other applications including shader processors. I'll risk an assumption that such non-professional transcoding tasks are currently the most adequate and useful application. The fact is, when users want to convert high-quality home video into a top-quality format, it makes sense to use a familiar codec they know how to configure. It does not matter how long it takes to complete a one-time or rare procedure. But if you need to prepare a video clip to publish in the Web or to compress video from a high-quality medium to a portable player, it's quite another matter. Encoding times are often critical here, because results in such situations are required immediately or never.

So what can ATI Stream offer to us? First of all, the menu of this utility now includes an option confirming that it's possible to enable hardware-assisted encoding and decoding.

Indeed, the H264 format can be encoded and decoded by the chipset. We've taken a 10-minute extract from Iron Man (1920x1080, 30 MB/s), "iPod Classic" profile (640x360). Besides, we've encoded DV video (720x576) into "YouTube" (H264, 480x360).

  HD Video ->"iPod Classic" DV ->"YouTube"
time, min:sec CPU, % GPU, % time, min:sec CPU, % GPU, %
Athlon II X2 250 + 780G
Athlon II X2 250 + 785G
Athlon II X2 250 + HD4850
Core 2 Duo E7400 + G45

Quite impressive results: encoding time in the heaviest first task has been halved! And CPU usage has never exceeded 90%. In other words, the chipset leaves enough CPU resources to promptly respond to user commands, so that you can do other tasks during encoding. Unfortunately, GPU-Z cannot monitor integrated GPU usage, so there is no way for us to know how much it was loaded by this task. But it's irrelevant.

Another interesting fact comes into view, when we compare results obtained with a graphics card. Radeon HD4850 just cannot be compared to any integrated solution in games, but they are practically on a par in transcoding. However, if we take into account CPU and GPU usage, the discrete card offloads a CPU better, and its GPU is not loaded much either. That's it's probably not a matter of power, but load balancing. However, from the practical point of view, you don't need a graphics card anymore, if you use it for transcoding only. From the point of view of MediaShow Espresso, there is still a difference, because the 785G failed to accelerate the second task, while the discrete graphics card manages to provide some performance gain. It's not very important, because even weak CPUs process easily-decodable formats (such as DV) at sufficient speed, especially in low resolutions. On the other hand, it's a question of program optimizations, so this support may appear in future.

  Intel G45 AMD 780G AMD 785G AMD 790GX
Video decoding (DXVA), CPU usage
FarCry 2 (Low@1280x720), fps
Devil May Cry 4 (Low@1280x720), fps
Crysis (Low@1024x768), fps
Crysis (Low@1280x1024), fps
S.T.A.L.K.E.R. Clear Sky (Static lights, High@1280x720), fps
S.T.A.L.K.E.R. Clear Sky (Dynamic lights, Low@1280x720), fps

Promised optimizations in video decoding have to do only with several parallel threads, which we don't test so far (but Windows 7 may change the situation, and this exotic mode may become a usual thing). What concerns a single thread, the presence of UVD (a special unit for HD video decoding inside a graphics core) is a step forward from the older schemes. Our test uses the same high-bitrate video extract from Iron Man.

Results in games are far from surprising as well, we could expect some performance gain only in S.T.A.L.K.E.R. Clear Sky, which supports DirectX 10.1. Indeed, there is some formal performance gain (although we didn't expect it, because we used low image quality settings that skip some special effects). However, AMD 790GX still takes the first place.

Power consumption of the entire system (measured by the Watt-meter integrated into the power supply unit)

  Intel G45 AMD 780G AMD 785G AMD 790GX
Text editing, W 28 16 14 20
Video decoding, W 25-40 19-36 19-31 24-36
FarCry 2 (Low@1280x720), W 40-70 41-56 35-55 48-60

Power consumption of a chipset depends on a given motherboard. Our reviews show that the spread of results among motherboards on the same chipset is very large.

For example, if we take a Biostar TA790GX A3+ with the 790GX chipset, its idle power consumption with the same processor (Athlon II X2 250) will be around 16-18 W. That is, the 780G and 790GX chipsets can reduce their power consumption in the idle mode to the similar level. And the 785G really looks like it consumes less power. We've used a full-size motherboard here, and they traditionally have higher appetites than microATX models, even if they use similar power circuitry. And the 785G also shows a little advantage in modes under load.

What concerns the system based on the Intel G45, this chipset is noticeably hotter. Heatsinks on all our motherboards have similar size, but the heatsink on the G45 easily exceeded 50C. And the ones on 790GX did not reach even 45C under prolonged load. It happens even though this ASRock motherboard features minimal chipset cooling compared to most other motherboards with the 790GX.


The most impressive improvement in the new chipset is certainly transcoding support. And it really works. It significantly accelerates the video conversion process and also offloads a CPU. So a computer remains responsive in other programs even during video encoding.

By the way, a graphics card is expected to demonstrate such features. Using graphics cards for generic computations was announced long ago. And now that it happens, users regard this feature from the practical point of view – there is nothing special about a powerful (and expensive) graphics card doing something more than games. It's another matter entirely for the integrated chipsets – a couple of years ago we didn't expect acceleration from such chipsets at all – they were used only for 2D. The practical component is apparent here – computers with integrated chipsets are rarely equipped with powerful quad-core processors that can smooth the effect from moving computations to a graphics core.

The new chipset also features routine improvements to lower power consumption at the same frequency level with the same fabrication process. On the whole, it's a very good Mid-End chipset.

How will it negotiate into the existing series? Motherboards with the 780G will be gradually pushed out, some successful products won't be discontinued, especially inexpensive ones. And the 790GX will preserve its positions until the next-gen chipset with higher performance in games rolls out. Besides, this chipset is used in many attractive motherboards for all-purpose computers designed for users who do not rely on integrated graphics and even use CrossFire. There are also many well-bundled full-size motherboards with the 785G planned, so they will expand your choice in this segment.

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