Most power supplies won't support Haswell's C6/C7 low-power states

By Shawn Knight
http://www.techspot.com/news/52423-most-power-supplies-wont-support-haswells-c6-c7-low-power-states.html

I guess I'm safe as i got ATX12V v2.3 ?

 

Just disable C6/C7 in the bios and it shouldn't be much of an issue..........hopefully.

 

this could be solved with a aftermarket regulator/capacitor setup I am sure the bigger vendors will come up with a solution

 

Any PSU with DC to DC won't be an issue.

 

Well I think I'm outta luck unless as mentioned it can be dealt with in the BIOS. The jonnyGURU review on mine states DC to DC regulation only for the minor rails (the listed spec makes that obvious). Nothing about the 12v one though.

"DC to DC regulation on the minor rails"
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=165



Seems to me saying "Any PSU with DC to DC won't be an issue" is kinda misleading since a lot of PSU manufacturers don't even say anything specific about 12v regulation specs. How many PSUs have DC to DC regulated 12v rails?

That said, I'm not sure it's that big a deal since Haswell seems geared more toward integrated graphics performance and laptop use with it's low power consumption. I doubt it's going to be much of an improvement for desktop gaming.

 

If a desktop PSU uses DC to DC, it's only going to be on the non-primary rails (+3.3V and +5V). The +12V is converted from the AC and then the non-primary rails are then converted from that.

You're not going to have +12V DC to DC. Where's the +12VDC going to convert from?!?

 

A thing I've been thinking about.

If the PSU is single rail, is this still going to be an issue, since there will most likely be other things pulling on the 12V?

 

Even if the PSU is multiple +12V rail, the CPU's rail is virtual. It gets its power from the same source as the other +12V rails. What makes it a separate +12V rail is just the fact that it's branched off and has an OCP limited on it.

This is a sleep state we're talking about, so if your fans, etc. are powered by the motherboard's fan headers, they too will go to sleep when the CPU does. The problem is memory, SSD's, etc. that are using +3.3V and/or +5V putting too great of a load on the PSU while the +12V is hardly loaded. This will cause the +12V to go out of spec (+12.6V and up) and prevent the computer from coming out of the sleep state without hard power cycling the power supply because the OVP protection in the PSU would cause it to latch off.

Most PSUs use DC to DC on these non-primary rails, so there's always a load on the +12V regardless of sleep state. The only PSUs you have to worry about are the group regulated ones like the FSP Aurum units that are out there. Most decent (say, 80 Plus Gold and up) use DC to DC for the non-primary rails because it's a much more efficient design than group regulation and the cost adder is only about $5 to $10.

Of course, if you do have a problem, I'm pretty sure you're going to be able to disable the C7 sleep state in the motherboard BIOS.

 

You can disable C6/C7 sleep states on the motherboard BIOS, i think...

And i believe that running on C6/C7 won't make you save a lot on the electricity bill also. Actually, $5 annually is my guess.

 

It hasn't been confirmed yet. Only speculated. But I assume to keep out of hot water the mobo manufacturers are going to have to allow disabling of C7 state.