Intel Haswell low power states could require a new PSU
If you get your freak on by an extreme low power state you may need to get a new power supply if you want to use the new C6/C7 low power states of Intel's upcoming Haswell processors. These new power states require a power supply that can maintain a minimum current load of 0.05A on the CPU exclusive 12V2 rail.
The previous ATX12V v2.3 design guidelines called for a minimum load of 0.5A on the CPU power rail, so a lot of older and budget power supplies will likely not meet the new specification, resulting in stability or shutdown issues once the system enters the C6/C7 power state.
Unfortunately, there's no way to know which power supplies are fully Haswell compliant as PSU manufacturers do not usually report the minimum load on their specification sheets.
Older or bargain basement power supply units may be unable to achieve this, and might become unstable or trigger a UVP/OVP shutdown once the system enters the C6/C7 power states. This is because the previous ATX12V v2.3 design guidelines for Ivy Bridge and its predecessors only called for a minimum load of 0.5 Amps on the CPU power rail, hence a less sophisticated internal feedback loop/protection could be used in older or cost-reduced offerings, which will not support the new standards.
Most worryingly, PSU manufacturers (even the enthusiast grade ones) do not usually report the minimum load on their spec sheets, so it is virtually impossible for us to come up with a list of supported units at this time. To ensure a smooth transition, mainboard designers and system integrators have been told to implement a BIOS-level toggle to enable/disable the new C6/C7 power states.
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Senior Member
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hmm, hopefully it wont be a issue
Senior Member
Posts: 1226
Joined: 2008-10-08
They are introducing even lower power states in Haswell?well for laptops and tablets it will be a nice feature to prolong battery life but seriously their desktop cpu's should have an option on motherboard's bios to disable these new C6/C7 low power states if they are going to be an issue with your power supply,A lot of power users have invested in expensive top class PSU's it would be frustrating for who ever will be upgrading to the new platform and find out that they don't meet the those requirements.
Senior Member
Posts: 2763
Joined: 2004-02-02
I'm for extremely low power usage, it needs to become more of a norm.
Senior Member
Posts: 25214
Joined: 2007-08-23
I don't believe it. AMD FX processors can use C6 without requiring a new PSU....
Also vr-zone doesn't mention a source for this info; any article that begins with "According to our sources" should be taken with a grain of salt imho.....
Senior Member
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Joined: 2008-01-06
Screw using low power designs! OVERCLOCK LIKE A BEAST!!!!