2 - AMD 790GX core logic

AMD 790GX core logic

In this test we'll use the Foxconn A7DA-S as the baseline test product. To understand the mainboard a tad better we need to explain the chipset. The AMD FX790 Chipset based platform includes the new SB750 Southbridge and AMD 790GX core logic. It's interesting to see AMD pursue this market again, as their strategy lately has been all about performance per dollar and product value. Well that still applies. To explain the chipset we need to have you look at the following block-diagram:

As you can see, the chipset is a bit difficult to position. It's feature rich, but what is it? A high-end board or a gamers mainstream chipset? We think it's both. The AMD 790GX Northbridge is coupled to the AM2+ socket through a HyperTransport 3.0 link.

The AMD 790GX core logic is build upon a 55nm fabrication process, which seems to be the key to AMD's success lately. It actually has a GPU embedded (Radeon HD 3300 Graphics Processor (IGP)) and includes support for DirectX 10, ATI Avivo HD, Unified Video Decoder (UVD). It supports 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. Also introduced with the 780G, the 790GX also supports SurroundView, for dual monitors in standard mode, or up to four displays using a dedicated graphics card.

Interfaces include support for DisplayPort, DVI and HDMI. The graphics core is virtually identical to the one found in the 780G chipset based products, but in the 790GX, it is clocked higher (700MHz) for up to 33% better performance. New is the presence of 128MB of onboard display 'cache' memory, which AMD has labeled as sideport memory. This actually is an option on the 780G, but you'll find it much more widespread on the 790GX motherboards, such as the Foxconn A7DA-S board we test today. It features 128MB of DDR3-1333 memory - on a 128-bit memory bus.

The 790GX supports ATI Hybrid CrossFireX that makes it possible to combine the integrated graphics with discrete ATI Radeon HD 3400 or ATI Radeon HD 2400 cards, which obviously is extremely low end. In its turn, the supported CrossFireX technology supports multi-GPU configurations based on ATI Radeon HD 4800 series just as well. We spot PATA, 6 SATA ports, HD audio, and 12 USB ports supported by the SB750 Southbridge. When you look a bit closer you'll see a a new feature called ACC, or Advanced Clock Calibration. More on ACC later though.

When we focus on the new SB 750 Southbridge chip then we see a new A-Link Express II interface that the SB750 Southbridge uses to communicate with the Northbridge.

Traditionally a Southbridge chip always support for both SATA RAID and IDE drives. The SB750 supports 6x SATA 3.0 Gb/s ports that can be setup in IDE, AHCI, JBOD, RAID 0, RAID 1, RAID 5 or RAID 10 modes, 12x USB 2.0 and 2x USB 1.1 ports, 6x PCI slots, HD Audio, IDE, and Serial and Parallel ports. A nice  improvement in the SB750 over the SB600 is the increase in USB 2.0 performance and the number of ports available. You'll now have a dual-channel controller sporting 12 USB 2.0 capable ports