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Thread: AMD 3870k wanting to re-enable turbo mode – is it possible?

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    AMD 3870k wanting to re-enable turbo mode – is it possible?

    I will be getting the AMD 3870k. I will be looking to Undervolt and Underclock to maximise power efficiency. However I want to know if there is a way to re-enable the turbo mode? As far as I’m aware, it is disabled since it is at a higher clock rate. Since I’m lowering the clock rate, I’m pretty sure this would then come in handy.

    Anyone know?

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    Not a good person scaryjim's Avatar
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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    AFAIK those processors - and indeed all the 100W Llano APUs - will report to the BIOS that they *don't* support turbo modes. I don't think there'd be any way to enable it without hacking the BIOS somehow, and that sounds like a bad plan to me

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    That's a crying shame if that were true. Well a shame for my purposes. I don't need the CPU running 99% of the time, but that 1% where it jumps would be very useful.

    That's the impressions i got as well. Anyone know for sure?

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    The CPU has lower idle clocks anyway - it will downclock itself automatically. Llano has very good idle power consumption.

    More details:

    http://en.wikipedia.org/wiki/Cool%27n%27Quiet

    The 65W A8-3800 does have Turbo Core:

    http://www.misco.co.uk/productinfo/p...AID=1081895198

    However,it does not hit the highest rated clockspeeds often and the A8-3800 is very hard to get hold off too.

    There is this 65W TDP A8-3820 for sale:

    http://www.ebay.co.uk/itm/A8-SERIES-...item5894d41edc

    It is £64 including postage from Spain,but the seller appears to sell a lot of AMD CPUs.

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    Another thought that just occurred to me is that, even if it was possible (say, by downclocking using the multiplier and finding a way in the BIOS to enable higher p-states) the fact that you're undervolting and underclocking would mean there'd always be TDP to spare so the processor would almost always be using the higher p-states when necessary, eliminating any benefit from the underclocking! As CAT says, C'n'Q will keep your idle power usage down to an absolute minimum anyway. Your best bet is to do a variety of power draw checks using your typical usage, tweak the voltage and clocks up and down until you get instability, and work out the best balance of power saving vs performance for you.

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    Right. Well the reason i'm going for the 3870k is because it has £10 cahsback from AMD. Which means i can get it for a little over £75.

    I will be getting the ASUS F1A75-I DELUXE (though i can't find any stock at the moment which sucks and will delay my build (look at my other threads for details). This board has very good voltage and clock controls too which should let me go as low as i can.

    The A8 3820 is very appealing though. But with the control i have over the 3870k i was thinking that it might actually be more efficient with better performance.

    Thanks Scaryjim, what you said is kind of what i thought. So lower voltage which would enable power saving at idle. But would underclocking have have additional benefit apart from lowering the "height" the cpu can go to.

    To expand, the CPU is rated at 3ghz. I have already undervolted. Now I underclock it to 2ghz. CnQ at idle is great so the clock speed would be very low. But then i use a program that kicks it into high gear. Would that mean that it can simply only go to 2ghz? This might be inefficient in itself...


    BTW love talking to people who know their stuff.

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    You've pretty much got the picture, yeah. Underclocking will set a maximum speed for the CPU, and once it hits that it will stop. Under low loads CnQ will drop the speed below that, to as low as 800MHz usually (although I've not got an A-series APU so I'm not 100% sure on the details), then when it needs the extra oomph it ramps back up to the normal clock speed.

    Underclocking has a couple of potential benefits for you. Firstly, it does reduce power draw, so an undervolted *and* underclocked CPU will draw less power at full load than if it's just undervolted (although you're balancing that with lower performance, of course). The second is that an undervolted CPU might not be completely stable it its default clock speed, which is set based on it using default voltage. Limiting the maximum clock speed could help to ensure that your system stays stable.

    Best bet is probably to lower the voltage a bit at a time then run a stability test (something like Prime95) until you get failure. Then drop the clock speed step by step at that voltage until you find a point where it's stable. Then repeat, until you get the best combination of voltage and clock speed for your needs.

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    Re: AMD 3870k wanting to re-enable turbo mode – is it possible?

    That, scaryjim, makes perfect and logical sense. Very very logical.

    I'm now struggling to find the ASUS itx motherboard. I wanted it because it's the best, has front USB 3 ports and wifi semi built in.

    But i can save a lot of money getting the Gigabyte, and getting a mini wifi USB3 dongle. (though reviews are hard to come by. Though i will be foregoing front case USB.

    So many choices. But going the gigabyte route looks to save me up to £40. Could get the whole thing closer to £500

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