Older or cheaper power supplies might have compatibility with the upcoming Haswell CPUs because they are too efficient.
Yesterday, we gave you a full roundup of all the rumors that we have reported regarding Intel's desktop lineup of Haswell CPUs. In the meantime, yet another rumor has surfaced. According to VR-Zone, a number of power supplies will actually not be able to support the Haswell CPUs, not because they cannot deliver enough power, they cannot deliver a low enough level of power.
While the Ivy Bridge CPUs had a minimum power consumption of 0.5 A in a C6 or C7 state, the next generation of processors would require only as little as 0.05 A, a 10x reduction. The problem is that a number of older or lower-quality power supplies are unable to deliver such low loads at stable voltages, meaning that the system could crash due to unstable voltages when in C6 or C7 state.
Fortunately, there is a solution. Users with problems could simply go into the motherboards' BIOS interface and disable the C6 and C7 power states. However, this would lead to higher power consumption. Fortunately though, most modern power supplies shouldn't have issues with the low power draw. A number of manufacturers are already advertising power supplies that have perfectly stable voltages even down to 0 W, among which is Enermax.