8-Series Chipsets, Revealed
Yes, Phenom II X6 is a drop-in upgrade for existing Socket AM2+/AM3 motherboards. But that’s not stopping the company from launching a handful of chipsets alongside its six-core CPUs. The 8-series chipsets logically replace older 7-series parts, even if they’re fundamentally similar.
Starting from the top of the stack, the 890FX succeeds the 790FX as AMD’s discrete graphics-only flagship. The northbridge component sports 42 total PCI Express 2.0 lanes, 32 of which can be used for graphics (2 x 16 lanes or 4 x 8 lanes), four of which are ganged into a 4-lane link, and six of which attach to x1 devices like USB 3.0 and gigabit Ethernet controllers.
890FX also supports IOMMU (input/output memory management unit), which, in a virtualized environment, allows virtual machines direct access to hardware components by remapping I/O DMA transfers and device-generated interrupts. There are a couple of good examples where this might be particularly useful. In a workstation environment, Nvidia’s SLI Multi-OS technology lets you assign a dedicated GPU in a multi-card setup to one particular virtual machine using an app like Parallels’ Workstation 4.0 Extreme. Or, you could assign a specific Ethernet controller to one performance-sensitive VM, cutting back on the performance penalty that you’d suffer otherwise. Intel’s version of this technology is called VT-d, and has been around for a while now.
Like 790FX, 890FX is manufactured on TSMC’s 65 nm node and fit into a 29x29 mm package. Aside from its slightly-expanded suite of PCI Express connectivity, the northbridge’s only real notable change is a doubling of the bandwidth between itself and the SB850 southbridge, from 2 GB/s to 4 GB/s.
|PCI Express||2.0 / 42 lanes||2.0 / 22 lanes||2.0 / 22 lanes||2.0 / 22 lanes|
|NB/SB Interface||x4 A-Link III|
|Integrated Graphics||-||Radeon HD 4290||-||Radeon HD 4250|
|Process Technology||65 nm||55 nm||65 nm||55 nm|
|Package Size||29 x 29 mm||21 x 21 mm||21 x 21 mm||21 x 21 mm|
|USB Ports||14 USB 2.0 + 2 USB 1.1||12 USB 2.0 + 2 USB 1.1|
|SATA||6 x SATA 6Gb/s||6 x SATA 3Gb/s|
|Integrated Gigabit Ethernet||Yes||-|
|Process Technology||65 nm||130 nm|
|Package Size||23 x 23 mm||21 x 21 mm|
Launched last month, the 890GX is less enthusiast and more mainstream. It’s limited to 22 lanes of PCI Express 2.0 connectivity and includes an integrated Radeon HD 4290 graphics processor. Support for DirectX 10.1, hardware acceleration for video playback, and Stream technology support don’t change the fact that integrated graphics is best reserved for folks who don’t do much in 3D-oriented applications.
890GX does support CrossFireX, though. It thus becomes possible to buy a relatively inexpensive motherboard based on 890GX and upgrade it over time to sport a couple of discrete graphics cards that split 16 lanes of PCIe into two x8 links.
Likewise, the AMD 870 chipset boasts 22 PCI Express lanes as well. But because the value-oriented part doesn’t support CrossFireX, its single 16-lane graphics link is reserved for single-card configurations (and not divisible into a pair of x8 links). You won’t find an integrated GPU in this northbridge—it’s decidedly a discrete graphics-only value part.
As with all of the other 8-series chipsets, AMD’s 870 employs the same 4 GB/s A-Link III interface with whichever southbridge motherboard vendors choose to pair it up with.
The entry-level integrated graphics chipset is still fairly well-equipped. 880G boasts 22 PCI Express 2.0 lanes, divisible into one x16 link and six x1 links. Its onboard GPU is called Radeon HD 4250, indicating its relative performance versus the 890GX’s Radeon HD 4290. Nevertheless, it still comes with video playback acceleration, Stream technology and post processing capabilities.
The SB850 Southbridge
While we’re not feeling the bandwidth bottleneck between northbridge and southbridge today, AMD’s integration of a SATA 6Gb/s controller onto its SB850 makes a data crunch much more plausible. Each 6 Gb/s port is theoretically capable of 600 MB/s. Times six ports, you’re looking at 3.6 GB/s. Factor in gigabit Ethernet and a pair of PCI Express 2.0 lanes (yes, the SB850 sports PCIe connectivity for the first time), and you’re in excess of the link’s throughput.
That’s not to say we’re in danger of getting anywhere close just yet. Storage devices are only just taxing the limits of 3 Gb/s SATA links, and it’s rare to see a gigabit Ethernet connection saturated as a pair of x1 PCI Express slots max out their potential bidirectional bandwidth. At the same time, it’s good to see AMD proactively prevent bottlenecks, especially knowing that motherboard manufacturers will be attaching USB 3.0 controllers and secondary network adapters to the southbridge.
As with southrbridge components prior, SB850 supports HD audio and its own PCI bus. SB850 also features up to 14 USB 2.0 ports.