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I am looking at putting together a collection of parts with a Haswell CPU in the middle.
My shopping list needs to include a new PSU because my last spare has just gone bang.
What is the actual consequence of a PSU not supporting the C6/C7 power states?
Will it just use more power, or fail to shut down properly?
For starters, virtually all good PSUs are haswell compatible, so if you were getting a good PSU anyway then you're fine. However, if it didn't support c6/7 then all that happens is you'd disable this on motherboard (in fact, you just wouldn't enable it, as it's usually disabled by default) and the CPU will use a fraction more power when the computer goes to sleep/parts of it are idle. That's all.
I agree with kalniel, just built my new haswell desktop 2 weeks ago.
Most good PSU are haswell ready, just make sure its not does cheap ones
I think haswell need those new energy saving PSU Erp or Eup (newer directive 2009)
The one I had my eye on is XFX P1-650S-UKB9. This is explicitly listed as not Haswell ready by the Scan blurb.
But I also noted that most other potential suppliers list it as out of stock and probably end-of-line.
I'm guessing that is why a reasonably good quality PSU is going for a reasonably cheap price.
Scan are wrong:Quote:
Originally Posted by liammcd
http://xfxforce.com/pt-br/Features/h...-supplies.aspx
I had a look at that link, but it does not mention the part number that I posted above.
However, after some fishing around on the XFX website (their own search facility doesn't find it either!), I came across the following:-
http://products.xfxforce.com/en-gb/P...U/P1-650S-UKB9
Apparently, yes, it does support the Haswell low-power states.
Do Scan review these pages?
I suppose it's not worth the effort for an end-of-life product...
It should do - P1-650S right?Quote:
Originally Posted by liammcd
Yes, it's a P1-650S, but your link only mentions the -NLB9 which is a different (and more expensive) beast to the UKB9.
I'm not sure what the difference is between the two, but the 'UKB9' seems to have what I need.
I'm a bit late but just wanted to add some information for potential future readers,
TBH I think a lot of this 'Haswell is so low power it needs a special PSU' is marketing plop blown out of all proportion by the media, like how 'Windows 8 boots so fast people couldn't get into BIOS menus' - POST time is completely independent of OS boot time.
Any half-decent modern PSU should work fine with Haswell, and most of them should work fine in the low power states; CPUs have had low single-digit idle power consumption for a good while now, and PSUs are often built to operate down to zero load. The motherboard itself, along with other components like HDDs, generally draw more power than an idle CPU anyway.
And it's even less of a problem with power supplies which derive the minor rails through a buck converter from the 12v rail - even with zero load directly on 12v, it will still be loaded indirectly through the minor rails.
And even if you find yourself with some PSU that freaks out with low 12v load, just leave the power state disabled like kalniel said.
But it's worth keeping the Haswell PSU compatibility issue in mind or you get something like this thread from yesterday:
http://forums.hexus.net/power-suppli...20w-4770k.html
Fairly sure that was the problem but the OP never did get back and say anything.
It's a possibility, but the OP claims to have a 7950 which will be pulling a few watts on the 12v rail when idle. We're talking 3W/0.25A lower load from the CPU. I'm not convinced.
If the power supply trips due to the CPU, it would be reasonable to expect it to trip on something like Ivy Bridge without the GPU, if it really is that close to tripping anyway.
Still, it's not the most modern PSU design, it doesn't use DC-DC for the minor rails, and may not be rated down to zero load. Unless the PSU is designed to shut off if current drops below a certain value on certain virtual rails (i.e. not a protection circuitry trip), but then the CPU connectors share rails with other connectors.
I've tried to search the net for any reports of people actually having related problems, but all I'm getting is page upon page of the same press releases.
Do you know whether my HX 750 would have the same problem with a 4670k?
You should be fine. The potentially problematic low-power states are usually disabled by default in BIOS anyway. So, you could try turning them on, see if you have any problems, and if so, just turn them back off.
Corsair's website also claims the HX750 should be fine even with the low-power states: http://www.corsair.com/us/blog/haswe...ower-supplies/
What is the problem with Haswell compatibility and power supplies? Is it simply that the new processor sleep states cause the CPU to draw even less current and the regulation drops-out on the power supply unless a minimum load is present?
Theoretically, yes, that is the problem. However practically there shouldn't be an issue.
I just disabled the c6/7 states in the motherboard by default. I think the only problem was that certain PSUs were unable to boot after being put to sleep