Haswell motherboards that can undervolt
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Author:  CA_Steve [ Mon Dec 16, 2013 9:18 am ]
Post subject:  Haswell motherboards that can undervolt

This information is hard to find. Hardly ever mentioned in reviews (poke -> MikeC ;0 ) and never mentioned at the mfgr's website or in the documentation. It's a PITA to buy a mobo and find it doesn't have this feature. Let's build a definative list. If you have first hand knowledge or can point to documentation, please post:

- motherboard mfgr and model
- How is the undervolting done:
- Setting CPU voltage (leads to fixed voltage and ignores speedstep, etc)?
- Setting CPU voltage offset (in conjuction with Adaptive Voltage Mode or other mode)?
- Offset range
- screenshot(s) or links.

- Z87 Extreme4: waiting for mfgr response.
- Z87 Extreme6: It appears UEFI ver 2.20 provides the ability for negative voltage in Vcore Voltage Additional Offset in conjunction with Adaptive mode.
- H87M Pro4: UEFI ver 1.70 provides ability for negative voltage in Vcore Voltage Offset.




Author:  mczak [ Mon Dec 16, 2013 11:01 am ]
Post subject:  Re: Haswell motherboards that can undervolt

I've got a Asrock H87M Pro4 and it supports negative and positive offsets just fine, with a range from way too low to work to kill your cpu instantly seemingly... It also has fixed voltage which I never tried.
You can forget about saving on your electricity bill at idle though, the difference isn't really measurable (probably thanks in part to the new c7 cpu state), at least not if you've got no equipment which can measure differences below 1W reliably :-). It definitely does make a difference under load though as expected.
Interestingly, the launch bios couldn't do it (there were plenty of options already but for cpu vcore only positive offsets were possible), however a bios update fixed that (there were 2 newer ones I don't know which one fixed it as I only tried the initial version plus the newest one).
Since motherboard manufacturers usually share most bios stuff between multiple boards I'd suspect most Asrock boards could do it - that you mention the Extreme6 also needing a newer bios for this to work would support that theory.

Author:  CA_Steve [ Mon Dec 16, 2013 1:32 pm ]
Post subject:  Re: Haswell motherboards that can undervolt

Thanks. Your latest BIOS is 1.70 dated 9/24/13. The Extreme6 is dated 12/4/13. Seems like they are rolling this out in a staggered manner.

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