Enermax Posts List of PSUs Compatible with Haswell Processors

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Jeffredo

That feature gets a big fat "who cares?" from me.

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Cregan89

Well the C6 power state has been around for awhile, the only difference with Haswell being that it uses almost 1/1000th of the power usage that previous architectures used. So unless your home's electricity is free, it adds up.

And C7 is just an extension of C6 which basically allows the CPU to enter and return from C6 quicker. And considering more and more operating systems put hardware into deep sleep mode instead of a full power off by default, this should mean quicker power down and boot up.

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nsvander

"deliver rock-stable voltages even at 0W load"

How do you deliver voltage with 0W load? I think someone failed begging electronics! W(Va)=VxA so if you have 0W then either the amps are 0 or the voltage is 0, if either are 0 then there is not flow, no flow mean its electrically off, electrically off, means nothing delivered!

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HVDynamo

You can still have a voltage with no current/no wattage. So in this case the amps are zero leading to zero watts while the voltage will still regulate to 12V. The point being that the power supply won't go into shutdown due to miss-regulation at lower power draw. Since most cheaper (80+ bronze and lower efficiency) supplies are group regulated they require a certain load on 12V to keep all the other voltages regulating properly. So, if 12V is at 0W the 3.3V and 5V lines should still regulate and supply current/power based on what they are saying. If I remember right, the voltages are within ATX spec if they are within 10% of the designated voltage (12,5,3.3, etc...). So in review, you are not delivering power at 0W load because Watts are a unit of power. But delivering voltage is as simple as delivering a potential difference, that does not require current to flow to be delivered. It is simply a state in which the supply is ready to supply current at that voltage. An example of that is your outlet in your house, 120VAC is always being delivered to the outlet (unless the breaker is open or there is an outage), but no current/power is being delivered to it until you plug something in and turn it on.

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NavarWynn

This would have more to do with the MB than the CPU. The MB 'feeds' the chip appropriate voltage and current (afterall, our chips do NOT run at 12v). In turn the issue is that the draw on the PS (in c6 or c7) falls below the PSU's ability to detect the load, and cycles itself. But I get it, they are simply trying to hype up a non-issue (to 99.99% of us anyway, and easily addressable for the other .01%), and use it as a marketing ploy.

Next!

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Cregan89

That's not actually the case with Haswell. Haswell is moving the voltage regulator directly onto the CPU itself, which is what allows it to be so power efficient in the first place.

Because of this, on most motherboard configurations, the motherboard could very well have a complete zero current draw in the C6/C7 power state. So total draw on the PSU in C6/C7 would really be 0.05A, worst case slightly higher.

And apparently the number of PSU's that won't operate at such a low current draw is actually a very large majority of them. And considering the continued prevalence for operating systems to drop into a low power state as opposed to a full power off by default, this very well could affect a large number of users.

Granted, the solution to this problem is quite simple (disable C6/C7). And I wouldn't be surprised to see motherboard manufacturers build in a failsafe mode for incompatible PSU's by applying a fake load on the PSU to keep it on.

Case in point, while it may only affect 0.01% of total PC users, it could affect a very large percentage of users upgrading their system or building a new one based on Haswell. So it is something to take note of.

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HiGHRoLLeR038

Sounds like marketing hype on Enermax's part. Nobody else has mentioned this potential issue.

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warlok180

It's quite real actually as reported here:

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

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Peanut Fox

Intel also has a list of power supplies that are known to work in C6/C7 states. http://www.intel.com/reseller/psu_selector/

EDIT: Which apperently this link is in the TechSpot article.

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HiGHRoLLeR038

thanks for the link! Looks like my AX850 is compatible

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wumpus

Is anybody familiar enough with Haswell to decrypt the marketing? A power supply provides a voltage. The load (the motherboard+chips) then draw a certain amount of current. If the power supply is working in spec, that is enough current (in this case down to .05A) at the correct voltage. A power suppy that can't do that will send the voltage (and thus typically the current, but don't expect it to be linear) out of spec.

Are they claiming that "brand X" simply fails and goes out of spec? Or that the motherboards are smart enough to notice that it went out of spec and change to a different mode (hopefully before causing errors and/or damage).

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warlok180

You will have to disable the feature in bios. For most desktop users, the power savings probably isn't a big deal; laptop users would benefit more in saving battery power.

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