Articles: Mainboards

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AMD 785G: Gigabyte GA-MA785GM-US2H

AT first glance the new AMD 785G chipset is not that much different from its predecessor, AMD 780G. Especially, if we look at its formal 3D specifications: the graphics core in both chipsets has the same number of shader processors (40) and the same number of rasterization units (4). Moreover, the GPU in both these chipsets works at the same frequency of 500 MHz. However, the graphics core in the new chipset is called Radeon HD 4200, while the GPU integrated into the AMD 780G was called Radeon HD 3200.

What was the reason for such serious change in the model name of the integrated graphics accelerator? Looks like AMD marketing people decided to stress the fact that the new graphics core supports DirectX 10.1. At the same time it is important to understand that it has very little effect on performance: the updated API version only offers additional options for shader optimization. Therefore, you shouldn’t expect the new chipset to run faster in any of the contemporary 3D applications.

However, what did change seriously is the part of the chipset responsible for video decoding. And even though the new chipset is not very different from its predecessor in the number of transistors or die size, the video decoder in AMD 785G was updated to version 2, which allowed it to perform simultaneous hardware video decoding of two data streams. It can be used during Blu-ray viewing when picture-in-picture mode is on.

The HDMI interface has also been updated to version 1.3 and now it can transfer 7.1 sound stream. However, since the audio part of the new chipset has been borrowed in full from the previous one, AMD 785G doesn’t support 8-channel LPCM sound. It is a pretty serious drawback that makes it questionable whether AMD 785G platforms can be used as a basis for high-end home theater systems, especially since the competing solutions from Intel do support eight-channel LPCM. However, if you are not one of the dedicated audiophiles, the absence of LPCM support won’t be such a big deal for you. Especially, since the new AMD chipset has no problems with any other popular formats such as multi-channel Dolby Digital or DTS.

Gigabyte provided us with their Socket AM2+ mainboard - GA-MA785GM-US2H – based on the new AMD 785G. This mainboard is one of the simplest example of how the new chipset could be used: it is designed for DDR2 SDRAM, not DDR3, and has no Sideport – a fast 128 MB cache based on DDR3 chips installed between the graphics core and system memory and slightly boosting the performance. Since these additional features are absent, the board sells at a very democratic price of about $80-$90 and is compatible not only with new Socket AM3 processors, but also with cheaper Socket AM2 CPUs.

At the same time, GA-MA785GM-US2H doesn’t look like a cheap product at all. Moreover, it uses only high-quality components and is built on Gigabyte’s brand name PCB with thicker conductive copper layers. However, solid-state capacitor with polymer electrolyte are only used for the four-phase processor voltage regulator circuitry, while most of the remaining capacitors or the ones with liquid electrolyte. Gigabyte also saved some money on the voltage regulator circuitry cooling, there are no heatsinks of any kind over it. Nevertheless, the board can work with all AMD processors, including the models with up to 140 W TDP. Therefore, the processor voltage regulator is powered via an 8-pin 12 V power connector instead of a common 4-pin one.

The functionality of this mainboard is quite sufficient for a performance fully functional system. Despite small MicroATX form-factor, the board is equipped with four DDR2 SDRAM slots, two PCI slots, a PCI Express x1 slot and even a PCI Express x16 2.0 slot that allows adding a fast discrete graphics card into the system. All slots and CPU socket are located in such spots that any large CPU cooler (a fanless one, for example) will fit perfectly in. Moreover, the board design is very convenient for system assembly, so the GA-MA785GM-US2H owner will not experience any difficulties with system building or cable management.

We are very pleased to point out that the BIOS of Gigabyte GA-MA785GM-US2H mainboard has all settings necessary to satisfy a computer enthusiast. The board allows you to overclock your processor as well as graphics core, as all needed options are there. However, there are certain limitations when it comes to voltage adjustment: memory voltage can be increased by no more than 0.3 V above the nominal (only to 2.1 V), while the CPU Vcore – only by 0.075 V.

However, there are options in the BIOS that allow enabling blocked cores in Phenom II X3 and Phenom II X2 processors.

Unfortunately, low price of this mainboard did have some effect on the chipset cooling system design: it is very primitive and consists of two stand alone aluminum heatsinks secured with plastic push-pin clips with springs. As a result, we were a little concerned about extremely high temperature of the chipset North Bridge during our test session. And even though it didn’t cause any problems, we assume that it would be dangerous to undertake any GPU overclocking experiments without modifying and improving the chipset cooling first.

The mainboard back panel has three monitor connectors: D-Sub, Dual-link DVI and HDMI. The mainboard also allows connecting two monitors simultaneously, although in this case you can’t use DVI and HDMI Outs together. Moreover, the existing DVI port is not compatible with a standard D-Sub adapter, which you should also keep in mind. There is also a PS/2 connector for keyboard or mouse, six USB ports, Gigabit network port, IEEE1394 connector and one eSATA port. The sound section is implemented via eight-channel Realtek ALC889A codec with very decent signal-to-noise ratio of 106 dBA.

Additional interface connectors are laid out as onboard pin-connectors. Overall, there are twelve USB ports, two IEEE1394 ports, serial and parallel ports, five Serial ATA-300 ports and a Parallel ATA port. By the way, since Gigabyte decided to use a relatively new AMD SB710 South Bridge, GA-MA785GM-US2H supports RAID 0, 1 and 0+1 arrays.

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