New South Bridge
The AMD 890GX sports the new South Bridge SB850. Frankly speaking, we don't think the SB750 chip that was used in AMD's previous chipsets is outdated, but the developer has just added a couple of hot features. First, it is a new Serial ATA controller that supports data-transfer speeds up to 6 Gbps. The AMD 890GX is in fact the world's first South Bridge to support the new interface. It must be noted, however, that the higher speed of SATA 6 Gbps is only a marketing advantage so far. It will only bring about tangible performance benefits when there appear appropriate SSDs capable of reading data at a speed higher than 300 MBps, which is the peak bandwidth of the current SATA-300 standard.
The support for the newest version of the SATA standard is not the only special feature about the SATA controller implemented in the SB850. AMD's engineers have given up using technologies they had previously licensed from Promise, so the new Serial ATA controller is AMD's own design.
Considering the SATA-600 implementation, it is rather odd that the AMD SB850 has no SuperSpeed USB 3.0. Instead, this South Bridge only offers 14 USB 2.0 ports. AMD suggests that USB 3.0 is implemented by means of external USB 3.0 controllers connected to the South Bridge via two PCI Express 2.0 lanes. This implementation ensures the full bandwidth of the new USB standard with data-transfer speeds up to 500 MBps.
Overall, the AMD SB850 looks a more advanced solution than its predecessor, yet some of highly anticipated features are still missing.
The SB850 does not have the exclusive Advanced Clock Calibration technology found in AMD's earlier South Bridges. It helped increase overclockability and power efficiency of first-generation Phenom processors and was later found suitable for unlocking disabled cores in dual- and triple-core Athlon II and Phenom II processors. At one time, AMD tried to block ACC for its new CPUs in the BIOS but a number of mainboards still support this technology. No wonder that it is now missing in the chipset. On the other hand, this does not mean that 890GX-based mainboards won't be able to unlock disabled CPU cores. For example, ASUS has successfully implemented this feature in its 890GX-based board, suggesting that users can still enjoy undocumented capabilities of AMD's dual- and triple-core CPUs.