What does "that PSU is not haswell ready" mean?
All PSUs are compatible with all CPUs right? This is what someone on one of my posts told me. It was a SeaSonic S12II with an i3-6100, which is Skylake (not haswell). What does this mean, or does this guy not know what he is talking about?
It's just with Haswell, Intel introduced some new C states (C6 and C7 I think), so you need a PSU that can provide low idle power to support those C states, but you can literally disable those C states and you won't have any problems.
So yes, all PSU's are compatible with CPU's, but some PSU's can't take advantage of all the features of a CPU.
Corsair Explains it here.
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.
See here for a description:
Skylake uses the same low power c-states as haswell I believe, so "haswell-ready" still applies. If you do get a non haswell ready psu, you can always disable the specific c-states that cause the issue in BIOS.
"Way back when the Intel Core i7-4770K and its kin first launched, there was some concern over power supply compatibility. Specifically, these processors added additional low power sleep states that could cause trouble with some power supplies. The new processors inherit these sleep states and the complications therein.
The overwhelming majority of power supplies support these sleep states without issue. However, if you purchase a power supply that doesn't support the lower power sleep states, you will need to disable them in BIOS."
Everything else should work - it is just the sleep states that have issues, and with the sleep states disabled, all power supplies should work with the new processors.