Intel's Haswell processor is just around the corner and if you are planning to pick up some new silicon, you'll likely want to keep reading. That's because it has been discovered that a number of power supplies currently on the market don't support Haswell's C6/C7 low-power states due to the fact they are unable to deliver less than 0.05 amps across the 12V2 rail according to a report from VR-Zone.
According to an Intel document viewed by the gang at The Tech Report, Haswell's C6/C7 states requires a minimum load of 0.05 amps on the 12V2 line. Power supplies that are older or budget models simply aren't capable of delivering such a small amount of juice. As a result, users with incompatible power supplies may experience stability problems or worse, the system may shut down completely if the PSU's under- or over-voltage protection kicks in.
The problem will be difficult to diagnose as most power supply makers don't advertise a unit's 12V2 rail specifications. Intel's Reseller Center website does have a list of power supplies that can be sorted by minimum 12V2 load. At present only 23 power supplies appear to be compatible with these new C6/C7 states: 19 from Corsair, three from InWin and one from Seasonic.
Corsair's Robert Pearce said he expects most motherboard vendors to disable C6/C7 by default in the BIOS as there are simply too many power supplies on the market that don't support the power-saving feature. He further noted that Corsair is working to ensure all of their power supplies are C6/C7 compliant.