Haswell Could Have Compatibility Issues With Old Power Supplies

/ 4 years ago


We know Intel’s Haswell is coming within the month or so, June the 4th to be precise, just in time for the Computex 2013 event. One of the main features you may have seen recurring from all the leaks and promotional material is that Haswell will maximise battery left better than Ivy bridge. This mainly refers to idle power consumption as load is going to be similar to Ivy Bridge. These improvements were mainly constructed and implemented for the mobile market to maximise Ultrabook battery life however they will also carry over to the PC platform.


To achieve massive savings in battery life, or power consumption for desktops, the Haswell CPUs are introducing two new idle states – C6 and C7. C6 and C7 allow Haswell to reduce power consumption by a significant amount more than Ivy Bridge. In fact it can drop its current to just 0.05 amps compared to 0.5 amps on Ivy Bridge, this means 10X lower power consumption at idle.


Now where does the power supply compatibility issue come into this? Well if your power supply is old, or cheap, then it may not be able to provide amps as low as 0.05 on the 12 volt rail. This is because entering those C6/C7 states could cause Under Voltage Protection (UVP) to be triggered or the power supply just might not be capable of delivering such a low amount of amps in a clean and stable way. On top of all this current power supply manufacturers don’t report minimum supported amps, only maximum, so it is impossible to tell whose power supplies will support what.

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However, it isn’t all doom and gloom because Intel have instructed motherboard vendors to provide a disable C6 and C7 state function in the BIOS so if you do have issues with running those idle states, then you can just disable them and the problem is fixed. Sure you won’t be able to use the extra power savings if you disable C6 and C7 but you will still be able to use your PC in a normal way.

What are your thoughts on C6 and C7?


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3 Responses to “Haswell Could Have Compatibility Issues With Old Power Supplies”
  1. interesting is how cpu can force signle 12V rail PSU to lower the amperage? is this article means power controllers on the mobo?

  2. d6bmg says:

    problem before release. Welcome to another episode of drama.

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