• Welcome to TechPowerUp Forums, Guest! Please check out our forum guidelines for info related to our community.

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

Joined
Sep 7, 2010
Messages
774 (0.20/day)
Processor Intel® Core™ i7-4790K
Motherboard Intel® Desktop Board DZ87KLT-75K
Cooling Intel® Stock Cooler
Memory G.Skill RipjawsX {F3-2400C11D-16GXM x 2 [32GB]}
Video Card(s) MSI GeForce RTX 2070 AERO
Storage Samsung 860 EVO 1TB mSATA SSD x2
Display(s) LG 32UL750-W
Case In Win F430
Power Supply Seasonic® Prime Fanless Titanium 600W
Mouse Dell™ KM714 Wireless
Keyboard Dell™ KM714 Wireless
Software Windows 10 Pro x64
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.

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 ?
 

MxPhenom 216

ASIC Engineer
Joined
Aug 31, 2010
Messages
12,498 (3.26/day)
Location
Longmont, CO
System Name Please god I need a GPU!
Processor Intel Core i7 8700k @ 4.8GHz 1.28v
Motherboard MSI Z370 Gaming Pro Carbon AC
Cooling 2x EK PE360 | EK CPU and GPU WB | Full hard line tubing | Singularity Resonance Single res/pump
Memory Corsair Vengeance Pro RGB 32GB 3200 14-14-14-34
Video Card(s) MSI GTX1070 Gaming X -> Asus TUF RTX3080 or Evga XC3 RTX3080
Storage 1TB Samsung 970 EVO 2TB Samsung 970 Evo Plus
Display(s) Dell S3220DGF 32" 1440p Freesync 2 (G-Sync) HDR 165Hz | 2x Asus VP249QGR 144Hz IPS
Case Lian Li PC-011D
Audio Device(s) Realtek 1220 w/ Sennheiser Game Ones
Power Supply Seasonic Flagship Prime Ultra Platinum 850
Mouse Razer Viper
Keyboard Razer Huntsman Tournament Edition
Software Windows 10 Pro 64-Bit
Just disable C6/C7 in the bios and it shouldn't be much of an issue..........hopefully. :rolleyes:
 

OneMoar

There is Always Moar
Joined
Apr 9, 2010
Messages
8,049 (2.02/day)
Location
Rochester area
System Name RPC MK2
Processor Intel Core i5 9600K@ 4.8Ghz 1.32V
Motherboard Asrock z390 phantom gaming 4
Cooling Enermax ets-t50
Memory CMK16GX4M2B3000C15 16GB DDR4-3000
Video Card(s) EVGA GeForce RTX 2060 XC ULTRA GAMING
Storage 512GB Intel 545s ssd 500GB ADATA SU800 ssd 1TB WD blue
Display(s) Cheap VA panel
Case Phanteks P300
Audio Device(s) onboard
Power Supply HX 750i
Mouse M65 Pro RGB
Keyboard K70 RGB
Software Windows 10 +startisback
this could be solved with a aftermarket regulator/capacitor setup I am sure the bigger vendors will come up with a solution
 
Joined
Nov 9, 2010
Messages
5,194 (1.38/day)
Processor Intel i7 950 @ 3.2GHz
Motherboard ASUS P6X58D-E
Cooling Corsair H50 push/pull
Memory Kingston HyperX 1600 8GB
Video Card(s) Sapphire HD 7970 OC
Storage Plextor M5P 128GB/WD Black 2x1TB,1x6TB/Seagate 1TB
Display(s) Panasonic TC-L32U3
Case Antec DF-85
Audio Device(s) Yamaha RX-V371 AVR
Power Supply XFX 850w Black Edition
Mouse Logitech G402
Keyboard Logitech K120
Software W10 Pro 64 bit
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.
 
Last edited:
Joined
Apr 24, 2007
Messages
159 (0.03/day)
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.

:wtf:

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?!? :roll:
 
Joined
May 6, 2012
Messages
785 (0.24/day)
Location
Denmark
System Name Waterfall | Iris
Processor Ryzen 5 1400 @ 3,5 GHz | i3-6157U
Motherboard ASUS X370-PRO | Acer laptop
Cooling Custom Watercooling | Stock laptop
Memory 4*8GB Various at 2133MHz | 2*4GB 2133MHz DDR4
Video Card(s) 2*R9 380 with WC blocks | Iris 550
Storage Intel 660 1TB + Crucial BX100 500GB | SK Hynix 256GB SSD + 640GB WD Blue
Display(s) U24E850R+U2515H | Internal 15,6"
Case Be Quiet! Dark Base 900 | Laptop
Audio Device(s) Monitor + Xenyx Q802USB | Realtek
Power Supply Seasonic Focus Plus Gold 750W | 65W 19V Power brick
Mouse Logitech M330 | Low end Logitech
Keyboard Logitech G610 Orion Brown |
Software Gentoo + Windows 10 Pro | Fedora
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?
 
Joined
Apr 24, 2007
Messages
159 (0.03/day)
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.
 
Joined
Oct 3, 2012
Messages
229 (0.07/day)
Location
Brazil
System Name Tiffany
Processor Intel i7 4770K @ 4.5Ghz
Motherboard Gigabyte Z87X-UD4H
Cooling Corsair H100i Push-Pull
Memory Corsair Vengeance 1600MHz 16GB
Video Card(s) XFX R9 290 Crossfire @ 925Mhz
Storage WD 500GB + Seagate 1 TB
Display(s) BenQ XL2420TX 120hz
Case Cooler Master CM690II Black & White
Audio Device(s) Onboard
Power Supply Cooler Master Silent Pro 1000W
Software Windows 7
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.
 
Joined
Apr 24, 2007
Messages
159 (0.03/day)
You can disable C6/C7 sleep states on the motherboard BIOS, i think...

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.
 
Top