Platform Support For FX: Make Sure It’s AM3+
When AMD launched its 990FX chipset (The 990FX Chipset Arrives: AMD And SLI Rise Again), there wasn’t much new to report aside from Socket AM3+ and Nvidia SLI support. But pushing out a platform update ahead of FX’s launch wasn’t a bad idea. After all, existing Socket AM3-compatible CPUs could easily drop into the 990FX-based motherboards, establishing a foundation for Socket AM3+ FX processors.
From my 990FX platform review: "You need the 942-pin Socket AM3+ (AM3b) interface, though, in order to support Zambezi’s power and frequency management features."
If you already own a Socket AM3+-equipped board, you need to flash its firmware with a Socket AM3-based processor installed before upgrading to an FX CPU. The firmware updates AMD’s AGESA (AMD Generic Encapsulated Software Architecture) to support the Bulldozer architecture.
Enthusiasts still running previous-generation Thuban- or Deneb-based Phenom IIs may not want to adopt these FX-enabling BIOS updates. We hear from the motherboard vendors that the performance of an older processor could be negatively affected by extensive changes made to the AGESA.
FX processors will not work in an AM3-based board. AMD deliberately blocked that combination out in its BIOS. Now, what if you’re rocking an 890FX-based motherboard with a Socket AM3+ interface? AMD isn’t explicitly supporting such a configuration, though Socket AM3+/890FX boards do exist. Compatibility could be a roll of the dice, but there isn't any specific reason a vendor claiming interoperability can't achieve it.
In addition to the 990FX chipset, AMD also supports Zambezi-based FX processors with its 990X and 970 chipsets. Of course, 990FX supports as many as four graphics cards through a 4 x 8-lane PCI Express 2.0 configuration (or you can do two true x16 slots). AMD’s 990X does up to two discrete cards through a pair of x8 slots (or one card in a x16 slot). Going the 970 route caps you at a single x16 slot for graphics; CrossFire simply is not supported on that platform.
Because AMD designs its own CPUs, chipsets, and graphics cards, it’s able to build complete platforms. Two years ago, the company’s Dragon platform included Socket AM2/AM2+ Phenom II processors, the 790 chipset, and Radeon HD 4000-series GPUs. Last year, Leo added the Socket AM3-based Phenom IIs, its 890-series chipsets, and Radeon HD 5000-series cards. In 2011, Scorpius centers on an AM3+-based FX, any of those three 900-series chipsets, and a Radeon HD 6000 add-in board.
On Unlocking Cores
All seven of the Zambezi-based FX processors employ the same silicon. Some of the processors have one Bulldozer module disabled, and some have two turned off. Seemingly, that’d set us up for the same sort of situation we saw when I got my hands on AMD’s quad-core Zosma processor, where a quad-core chip based on a hexa-core die could be unlocked to enable all six cores. Apparently, AMD says that won’t happen this time around. The company claims to have disabled the way in which this might have been possible. It's instead cranking up the clocks on SKUs with fewer cores, Turning on that disabled logic could cause stability issues.
With all of that said, we heard that core unlocking wasn’t possible a couple of years ago. And yet, we still managed to get several Phenom II X3s unlocked. We won’t close the door on the FX until motherboard vendors start confirming they can’t take a, say, FX-4100 up to something similar to an -8150.