The prospect of using a chipset with integrated video would be enough to send most gamers over the edge. After all, many of these onboard GPUs don't even support the majority of 3D games, and even if it can play the game, the overall performance will either result in a slideshow at standard settings, or terrible image quality when detail levels are dropped.
This scenario started to change a bit with the release of the AMD 780G chipset. This chipset offered an integrated HD 3200 GPU, and while not that powerful, it did have the same features and software support as other HD 3000 series cards, and could link up in multi-GPU Hybrid Graphics mode. But there were some noted issues, such as the inability to handle higher-TDP Phenom X4 processors, and a design that was decidedly entry-level.
The AMD 790GX looks to alleviate these concerns, and its design is like melding the best from the AMD 790FX and 780G chipsets, and creating a high-end chipset but with integrated graphics. This is a very interesting strategy, and not only have many of these features been ported over, but some have been improved as well. For starters, the integrated video has been upgraded from HD 3200 of the 780G to the faster HD 3300 mGPU found on the 790GX.
The AMD 790GX Northbridge is similar to the 790FX, but with some noted differences. It features HyperTransport 3.0 (41.6 GB/s of aggregate bandwidth), support for up to DDR2-1066, a single x16 PCIe 2.0 slot (or dual PCIe x8 slots), up to six PCIe x1 slots, a DVI/HDMI/DisplayPort w/ HDCP interface, and a Unified Video Decoder. It supports all AMD AM2/AM2+ processors, from the fastest Phenom X4 down to the entry-level Sempron.
Like the 790FX, the AMD 790GX supports dual-GPU CrossFireX technology and can handle Phenom processors up to 140W. This allows the AMD 790GX to exist as a performance chipset, with all the overclocking and power that enthusiasts demand, but with integrated graphics built-in. In the AMD hierarchy, it fits right in between the AMD 790FX and 790X chipsets.
In addition, AMD has also added a new SB750 Southbridge, which supports 12 USB 2.0 connections and 6 SATA 3.0Gb/s with RAID/eSATA functionality. It links to the 790GX Northbridge using a high-speed A-Link Express II interface, and includes a single PATA channel, a HD audio controller, and Advanced Clock Calibration. This last option works with AMD OverDrive to provide the latest in Phenom overclocking.
The 55nm AMD 790GX joins the 780G as integrated chipsets with a full DirectX 10 core. The two differ in terms of model numbers, as the 780G sports the Radeon HD 3200, while the 790GX includes the upgraded HD 3300. The two graphics cores are identical in terms of base architecture, but Radeon HD 3300 is clocked at 700 MHz, compared to only 500 MHz on the HD 3200.
The 700 MHz GPU clock is matched with a 400 MHz/800 MHz DDR2 effective memory speed, which translates into an overall fillrate exceeding that of a 600 MHz Radeon HD 3450. The naming convention does seem a bit strange, as this model would be more in line with a hypothetical HD 3460 GPU, as the HD 3470 is clocked at 800 MHz. One reason may be that the memory bandwidth is tied to the system memory and the speed and latency of the DDR2.
But one area that can improve performance is the presence of up to 128MB of onboard display cache memory, which AMD has dubbed sideband (or sideport) memory. This is an option on the 780G, but you'll find it much more prevalent on the 790GX motherboards, such as our Foxconn A7DA-S board, which features 128MB of DDR3-1333 memory. This can provide higher gaming performance, up to a 15% increase according to Foxconn, and we'll put it to the test in our benchmarking. The HD 3300 also supports Hybrid Graphics technology (pictured below), where the onboard HD 3300 GPU is matched with a Radeon HD 2400 or 3450/3470 video card in CrossFire mode.
The AMD 790GX also includes a UVD (Unified Video Decoder), which along with Avivo HD, helps with standard and HD video playback. It has support for MPEG-2, VC-1, and H.264 playback, and the HDCP compliant outputs ensures Blu-ray/HD-DVD output for your PC or big screen. The 790GX also supports SurroundView, for dual monitors in standard mode, or up to four displays using a dedicated graphics card. AMD has made some power savings enhancements with the 790GX, offering a deep sleep mode for the sideband memory, voltage scaling, enhanced PowerPlay features, and a new lower power CPU state.