AMD 7-series chipsets, along with Incy Wincy Spider
We've told you already that AMD's Phenom processor needs an AM2+ chipset-based motherboard to realise its full performance and power-saving potential.
Complementing the new processor and recently-released Radeon HD 3800-series graphics cards is a new core-logic from, well, AMD. Welcome to the 7-series chipset family.
| Chipset | CPU support | Northbridge | Southbridge | PCIe x16 slots (mechanical) | PCIe standard | HyperTransport | CrossFire support | Overclocking | Price |
|---|---|---|---|---|---|---|---|---|---|
| AMD 790FX | AM2+ | RD790 | SB600 | Up to 4 | 2.0 | 3.0 | Yes, CrossFire X | Extreme | £99+ |
| AMD 790X | AM2+ | RD780 | SB600 | 2 | 2.0 | 3.0 | Yes, CrossFire | Enthusiast | £79 |
| AMD 770 | AM2+ | RX780 | SB600 | 1 | 2.0 | 3.0 | No | Basic | £59 |
The AMD 7-series will initially have three members but these will be joined in Q1 2008 by a version with an integrated graphics processor - RS780. As you'd expect, the family members share a number of traits. These include AM2+; PCIe 2.0; HyperTransport 3.0; and southbridge SB600 support, as found on the incumbent RD580.
Let's take a closer look at the range-topping AMD 790FX.
The chipset is able to accommodate every AMD AM2/AM2+ processor but the nature of this high-end chipset will, most likely, see the socket populated by a quad-core Phenom.
The RD790 northbridge is based on a 65nm manufacturing process and, AMD claims, offers a 10W TDP, compared to Intel X38's 26W. Memory access runs through a dedicated interconnect to the memory-controller located within the CPU. As we noted earlier, the Phenom range supports DDR2-1066 modules.
A HyperTransport 3.0 link hooks up the RD790's northbridge to the processor and operates at an effective 3.6GHz. The northbridge follows Intel's lead and offers PCIe 2.0 support, doubling the bandwidth to/from the add-in card and system. In the case of a PCIe x16 slot for graphics cards, that's 8GiB/s in each direction (5Gbit/s on 16 lanes). Note that the chipset is fully backward-compatible with cards that use PCIe 1.1.
The precise physical arrangement of the x32 PCIe 2.0 lanes reserved for graphics will be decided by makers of motherboards. We envisage that most partners building on the 790FX core-logic will equip their boards with either three or four mechanical x16 PCIe slots, bringing Tri-Fire and CrossFireX support. Of course, such an action requires a reduction of the bandwidth to each card. So in a CrossFireX four-card set up, each GPU would be given an eight-lane PCIe 'highway'.
A further six PCIe 2.0 lanes are reserved for peripherals - RAID cards and so forth. Note that the lanes provide double the bandwidth available from PCIe 1.1.
In a bid to ensure that RD790 boards ship quickly, AMD has decided to use the established SB600 southbridge, which connects to the northbridge over a four-lane PCIe bridge. The southbridge has no further PCIe lanes of its own, although it does support up to six PCIc slots, along with native command-queuing; four SATA ports with AHCI; RAID0/1/10; 10 USB ports; and high-definition audio.
To create a feature-rich motherboard, designers will need to provide discrete Ethernet controllers and, most likely, additional SATA support.
AMD claims that the RD790 has been designed with extreme overclocking in mind. To that end, retail RD790 motherboards will ship with extensive BIOS-tuning options and AMD's OverDrive software: OS-based tweaking software that hooks in with Windows Vista and provides a surfeit of options for overclocking and performance-tuning.
If run with a Phenom CPU, AMD OverDrive gives the user control over the each core's speed, various voltage rails and a comprehensive system-monitoring overview.
We'll take a look at some of the options during our visual tour of the MSI K9A2+ Platinum.
For the more basic AMD RD780 chipset, quite a few features have been left out - three-way and four-way CrossFire support; granular control over OS-based tweaking; and a few extreme BIOS options. However, it will ship with at a lower price and be used in the volume-selling mainboards.
On the lower end of the scale is the budget RX770 that ships with a single PCIe x16 slot and basic overclocking - in the BIOS- and within the operating system. Support for DDR2-1066 is also likely to be stripped out.
Summary
The AMD 7-series chipsets appear to provide a decent platform for the Phenom processor, even though the southbridge, carried over from the RD580, is a little lacking. However, two replacement southbridges are promised in the next few months - the SB700 and SB750.Incy Wincy Spider
We've managed to get this far without talking about the entire platform proposition - CPU, chipset and graphics card - which AMD dubs 'Spider'. The company recently launched its mid-range DX10.1-supporting Radeon HD 3870 and HD 3850 graphics cards that take advantage of PCIe 2.0, and which we reviewed last week.
Here, we've covered the quad-core Phenom processors that interface with the system via a HyperTransport 3.0 bus and the final member of the triumvirate, the 7-series chipset, takes advantage of both, offering four-card CrossFire (790FX) allied to support for AM2+ CPUs.
There's no reason why you couldn't run an AMD Athlon 64 X2 processor and NVIDIA PCIe 1.1 graphics card on a motherboard based on new-generation AMD chipset, of course, but the Spider platform has inherent synergies among its family members and, uniquely, allows you to use Phenom CPUs (which NVIDIA's 590i SLI chipset still doesn't support) and graphics cards set up in CrossFireX configurations.
Somewhat bizarrely, AMD will not be pushing the Spider platform as a brand the way, for instance, Intel has successfully promoted Centrino. No, instead it will be up to its partners to hammer home the advantages of the platform. We'll be taking a look at the overall value proposition later on in this review.
By the way, can you guess why the platform is dubbed Spider? Answers in our forums, please.
