Intel's upcoming Haswell CPUs have a new sleep state that draws just 0.05A on the 12V rail—one tenth the idle draw of existing Ivy bridge chips. Not all PSUs can supply that little 12V current, and those that can't may have problems waking Haswell from its lowest-power state. Corsair and Seasonic have already detailed which of their PSUs are compatible with Haswell's new sleep state. Today, it's Fractal Design's turn.
In a press release (PDF) that hit our inbox this morning, Fractal Design confirms that all of its Newton R3 and Tesla R2 PSUs support Haswell's low-power state. Those units employ DC-to-DC conversion to generate 3.3 and 5V power from the 12V line, so there will always be an additional 12V load.
Fractal's Integra R2 PSUs don't use DC-to-DC conversion and instead rely on the "group regulation method" to generate 3.3 and 5V power. Output voltages can be affected if there's a large discrepancy between the loads on those rails and the 12V line, the press release says. Based on internal testing, Fractal expects those voltage fluctuations to be within the range allowed by the ATX specification "for any load levels on 3.3V and 5V likely to occur during system sleep."
Despite the results of its internal testing, Fractal lists the Integra R2 as "likely compatible" with Haswell. The press release claims Intel still hasn't released its "testing methodology or a formal definition of Haswell compatibility," making it difficult to guarantee the Integra won't have issues. With Haswell less than two weeks away, I would have expected Intel to be working more closely with PC component makers to ensure compatibility.