It makes for great headlines to say that the new AM3 Phenom II processors are “plagued” by a DDR3-1333 bug. Fanboys and girls love to jump and point fingers, nevermind getting to the heart of the matter. We take a different approach at Icrontic, and we called AMD to get the story.
Is there a problem with the integrated memory controller in the Phenom II that makes it incapable of handling four sticks of DDR3-1333? Why would they downclock your RAM to a slower speed?
Damon Muzny, a PR representative at AMD, took the time to explain the situation. Yes, the Phenom II doesn’t “officially” support four sticks of DDR3-1333 or DDR2-1066. Internal testing showed that four sticks triggered instability in multiple test platforms when using standard JEDEC voltages and speeds. Two high-speed sticks on a single channel can push the memory controller’s limits; combine that with subtle variations in motherboard architectures, and inter-component signaling can become erratic.
“We had to make a choice,” Muzny said. “It was enough of a problem that we had to make a choice.”
Overclockers know that a bump in voltage is the easiest way to fix memory instability. A little extra juice in the system keeps things working correctly and will allow users to fill all four memory slots on their motherboards.
According to Muzny, AMD had three options for rectifying the Phenom II’s memory situation:
- No official support of DDR3-1333 and DDR2-1066 in any capacities.
- Require motherboards to run outside of JEDEC voltage specifications when they detect two memory sticks on a single channel.
- Clock memory down to fail-safe speeds.
Muzny said not supporting DDR3-1333 and DDR2-1066 would be a terrible choice because both speeds work, and requiring motherboards to run out of official specifications still left room for instability or legal troubles. Downclocking was the safest bet catering to the lowest common denominator and, as such, motherboard manufacturers were instructed to have the BIOS downclock DDR3-1333 to DDR3-1066 and DDR2-1066 to DDR2-800 to ensure stability.
“We have to take the most conservative approach,” Muzny said.
Overclockers and enthusiasts are still encouraged to manually set memory parameters for stable operation. After all, the most popular overclocking RAM already runs well outside specification. In the end, it’s nothing new. It’s just AMD playing things safe.
According to Muzny, future chip revisions could address the issue, but the problems aren’t just caused by the Phenom II’s memory controller. Motherboard manufacturers will need to use quality components to ensure clean, clear signals if they want to do their part.