A report recently published over at the VR-Zone discussing the new 4th generation Intel Core processors, code-named "Haswell", and their ability to go into a lower power sleep state than any previous processor has caused some concern about PSU compatability with the new processor.

When an Intel Core (i3, i5, i7) processor is idle, it goes into a sleep state that requires less power than when the CPU is active. Since the motherboard voltage regulation modules that provide power to the CPU gets their power from the power supply's +12V rail, these sleep states can dramatically reduce the load on the power supply's +12V rail.

According to Intel's presentation at IDF, the new Haswell processors enter a sleep state called C7 that can drop processor power usage as low as 0.05A. Even if the sleeping CPU is the only load on the +12V rail, most power supplies can handle a load this low. The potential problem comes up when there is still a substantial load on the power supply's non-primary rails (the +3.3V and +5V). If the load on these non-primary rails are above a certain threshold (which varies by PSU), the +12V can go out of spec (voltages greater than +12.6V). If the +12V is out of spec when the motherboard comes out of the sleep state, the PSU's protection may prevent the PSU from running and will cause the power supply to "latch off". This will require the user to cycle the power on their power supply using the power switch on the back of the unit.

While we are still working with Intel on the details of the testing methodology they use to check PSUs for Haswell compatibility, it is already known that a power supply that uses DC to DC for the non-primary rails (the +3.3V and +5V) will not have an issue with the new low power sleep states. This is because a DC to DC buck converter is used to convert +12V to +3.3V and +5V. This means that no matter what load the CPU puts on the power supply, there will always be a load on the +12V because the +12V is required to provide power to +3.3V and +5V.

Corsair utilizes this DC to DC technology in most of their power supplies. Starting with the CX750 and CX750M and moving all of the way through the GS Series, TX and TX-M Series, the HX Series, both the AX Series Gold and AX Series Platinum, and the new AXi Series. So whatever your budget, if you choose Intel's new Haswell processor and wish to utilize the new, low power C7 sleep state, Corsair has a power supply for you.

PSU Series Model Haswell

Compatibility Comment AXi AX1500i Yes 100% Compatible with Haswell CPUs AX1200i Yes 100% Compatible with Haswell CPUs AX860i Yes 100% Compatible with Haswell CPUs AX760i Yes 100% Compatible with Haswell CPUs AX

(Gold and Platinum) AX1200 Yes 100% Compatible with Haswell CPUs AX860 Yes 100% Compatible with Haswell CPUs AX850 Yes 100% Compatible with Haswell CPUs AX760 Yes 100% Compatible with Haswell CPUs AX750 Yes 100% Compatible with Haswell CPUs AX650 Yes 100% Compatible with Haswell CPUs HXi HX1200i Yes 100% Compatible with Haswell CPUs HX1000i Yes 100% Compatible with Haswell CPUs HX850i Yes 100% Compatible with Haswell CPUs HX750i Yes 100% Compatible with Haswell CPUs HX

(Silver, Gold and HX1000) HX1050 Yes 100% Compatible with Haswell CPUs HX1000 Yes 100% Compatible with Haswell CPUs HX850 Yes 100% Compatible with Haswell CPUs HX750 Yes 100% Compatible with Haswell CPUs HX650 Yes 100% Compatible with Haswell CPUs HX

(Legacy Bronze

and below) HX620 TBD Likely compatible — currently validating HX520 TBD Likely compatible — currently validating HX650 TBD Likely compatible — currently validating HX450 TBD Likely compatible — currently validating TX-M

(All Versions) TX950M Yes 100% Compatible with Haswell CPUs TX850M Yes 100% Compatible with Haswell CPUs TX750M Yes 100% Compatible with Haswell CPUs TX650M Yes 100% Compatible with Haswell CPUs TX550M Yes 100% Compatible with Haswell CPUs RM

(All Versions) RM1000 Yes 100% Compatible with Haswell CPUs RM850 Yes 100% Compatible with Haswell CPUs RM750 Yes 100% Compatible with Haswell CPUs RM650 Yes 100% Compatible with Haswell CPUs RM550 Yes 100% Compatible with Haswell CPUs RM450 Yes 100% Compatible with Haswell CPUs TX

(All Versions) TX950 Yes 100% Compatible with Haswell CPUs TX850 Yes 100% Compatible with Haswell CPUs TX750 Yes 100% Compatible with Haswell CPUs TX650 Yes 100% Compatible with Haswell CPUs TX550 Yes 100% Compatible with Haswell CPUs GS

(Current V3) GS800 Yes 100% Compatible with Haswell CPUs GS700 Yes 100% Compatible with Haswell CPUs GS600 Yes 100% Compatible with Haswell CPUs GS

(Legacy V2) GS600 TBD Likely compatible — currently validating GS500 TBD Likely compatible — currently validating GS

(Legacy V1) GS800 Yes 100% Compatible with Haswell CPUs GS700 Yes 100% Compatible with Haswell CPUs GS600 Yes 100% Compatible with Haswell CPUs GS500 TBD Likely compatible — currently validating CS-M CS850M Yes 100% Compatible with Haswell CPUs CS750M Yes 100% Compatible with Haswell CPUs CS650M Yes 100% Compatible with Haswell CPUs CS550M Yes 100% Compatible with Haswell CPUs CS450M Yes 100% Compatible with Haswell CPUs CX-M CX850M Yes 100% Compatible with Haswell CPUs CX750M Yes 100% Compatible with Haswell CPUs CX600M TBD Likely compatible — currently validating CX500M TBD Likely compatible — currently validating CX430M TBD Likely compatible — currently validating CX CX750 Yes 100% Compatible with Haswell CPUs CX600 TBD Likely compatible — currently validating CX500 TBD Likely compatible — currently validating CX430 TBD Likely compatible — currently validating VX

(Legacy) VX450 TBD Likely compatible — currently validating VX550 Yes 100% Compatible with Haswell CPUs VS VS650 TBD Likely compatible — currently validating VS550 TBD Likely compatible — currently validating VS450 TBD Likely compatible — currently validating VS350 TBD Likely compatible — currently validating

Alternately, you can visit Intel's "PSU Selector Tool" located here.

To filter the PSUs that are considered by Intel to be "Haswell Ready", start by changing the value of the "12V2 Min-load 0A" to "Yes".

As we work with Intel over their Haswell testing methodology and discuss with motherboard manufacturers about the different ways they may address potential compatibility problems with power supplies, we will keep you updated right here on this blog. We will also continue to test legacy product (discontinued product) and keep the list updated in this way as well.