AMD's 785G Chipset - Revolutionary or Evolutionary?

Introduction

Remember when ATI made crappy chipsets that no one bought, and all AMD systems were built with NVIDIA or even VIA chipsets? Yeah, that memory is fading for us too.

Today we get to officially unveil the 785G, the latest in integrated graphics chipsets by AMD for AMD. As the name implies, there is very little separating 785G from its predecessor (780G) and we’re quite ok with that. In fact, the only reason not to get a 780G is addressed by the 785: the new chipset supports 8-channel LPCM audio over HDMI. The lack of TrueHD and DTS-HD audio bit-streaming remains but neither is this feature supported on other chipsets. We also see a jump from HDMI 1.2 to 1.3 standards. Update: This story is developing in real time but AMD is telling us that 8-channel LPCM over HDMI is not supported in the final chipset. More info here.

The rest of the major improvements are strictly related to video playback duties. We jump from Universal Video Decoder (UVD) 1.0 on the 780G to UVD 2.0 capabilities on the 785G. The video decode engine supports decoding multiple HD streams (useful for picture-in-picture on a Blu-ray movie) and additional post processing effects if you are not a big video purist. Also new is the 785G's ability to perform detail enhancements on the fly.

The graphics side has not really changed that much. The new GPU is based off the RV620 core and is roughly the same size/complexity as the old one. In other words we get the same 55nm node process and almost the same amount of transistors, just a tad over 205 million.The 785G’s PowerPlay technology is improved with the core constantly adjusting clock speeds based on GPU utilization with a 60MHz target when idling compared to 500MHz at full load. AMD adds DirectX 10.1 support but stream processor count and clock speeds have not changed. Thus gaming performance remains mostly unchanged.

And in this corner: Intel

AMD is targeting Intel’s G41 with this 785G, and by simply by adding 8-channel LPCM and UVD 2.0 support it is no longer at a feature deficit for the HTPC audience. In fact, we cannot find one area where the 785G comes up short compared to the G41.

Intel’s G41 is a cost-reduced version of Intel’s G45 chipset. You lose PCIe 2.0 support (1.1 only) and integrated Gigabit Ethernet (only 10/100). Considering Intel recommends mating the ICH7 Southbridge to the G41 for cost purposes, you also lose RAID support, four USB ports, and two 3GB/s SATA ports compared to the AMD SB710.

The Radeon HD 4200 is where all the action is with this update but the more things change, the more they remain the same. We still have the traditional Northbridge/Southbridge layout with the NB supporting a 2GHz HyperTransport link compatible with the latest Socket AM3 processors. The 22 PCI Express 2.0 lanes are still around along with the four lane PCI Express 1.1 lanes supporting the A-Link Express connection between the two bridges.

The NB splits its 22 lanes between a single x16 link for graphics and six x1 links for expansion slots and onboard peripherals. Technically, the 785G chipset can't split its x16 graphics link into two x8 links for CrossFire X operation. The 785G supports hybrid CrossFire operation, but only with the older HD 3450/3470 video cards. We recommend skipping this feature, for now.

The SB710 is essentially an updated SB700 with ACC (Advanced Clock Calibration) support, or looking at it a different way, a cost reduced SB750 without support for RAID 5 arrays. The SB710 has six 300MB/s Serial ATA ports with RAID 0, 1, and 0+1 support plus a single IDE port supporting two drives so JMicron and Marvell are held at bay on these systems. Twelve USB ports and a high-definition audio interface round out the SB710 as native GbE support is still missing.

It would have been nice to see next-gen USB and SATA support but that will have to wait for the SB8xxx updates next year. However, compared to the ICH7 mated with the G41, the SB710 is positively feature rich at the same price point.

We could continue on with subtle hints about why this chipset is a better alternative than the Intel G41 or its 780G/790GX siblings, but the bottom line is that AMD has taken an evolutionary step with this chipset, one for the better. That said, let's see how it performs against the other chipsets in its class.