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Dialing In Our Overclock Using The Right Components

Professional Help: Getting The Best Overclock From AMD's A8-3870K
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As much as we’d like to push the A8-3870K as far as possible, it doesn’t make sense to overspend on high-end water cooling and the most exotic memory when we're working with a $120 APU. This needs to make sense for value-oriented overclockers. So, here are the core components we chose:

A8-3870K Overclocking Project
MotherboardAsus F1A75-V Pro
Socket FM1, AMD A75 FCH
$120
ProcessorAMD A8-3870K
3.0 GHz, Quad-Core
$120
MemoryCorsair Vengeance 4 GB (2 x 2 GB) DDR3-2000
Dual-Channel Desktop Memory Kit
$55
CoolerCooler Master Hyper TX3
$20


Despite our goals, we maintained a reasonable budget. Cooler Master’s Hyper TX3 is a cost-effective unit that's worlds better than what AMD bundles with its A8-3870K. Corsair’s Vengeance modules are rated for operation up to 2000 MT/s, they have a good reputation for overclocking, according to hwbot.org, and they won't break the bank at $55. Finally, Asus’ F1A75-V Pro has an excellent reputation for Llano-based overclocking.

The rest of the components are just as critical. We're using a decent power supply rated at 500 W and a case with decent airflow.

Overclocking

Sami suggested that we start by overclocking the GPU, then the CPU, followed by the reference clock, and finally the memory.

But before we start stressing components, let’s look at the motherboard's BIOS to ensure its supporting settings are configured as we want. Here are the power delivery settings we want from Asus' F1A75-V:

Now, we're ready to see how far we can push the GPU. With our northbridge voltage manually set to 1.3 V, we're able to push the graphics engine to 960 MHz stably. That's not a bad outcome considering the GPU operates at 600 MHz from the factory.

Next comes the CPU. Although we were able to boot into Windows as fast as 3.8 GHz, the highest stable frequency that was able to handle a Prime95 stress test was 3.6 GHz at 1.5 V. That's not an incredible increase, but it does make an appreciable difference compared to the stock 3.0 GHz clock rate.

With the CPU and GPU limits established, it's time to see how far we can take the reference clock. We set the SATA controller to IDE mode, used the digital DVI output, and saw success at 132 MHz, which is up from the stock 100 MHz.

At this point, we haven't yet tackled the memory. We're really just trying to isolate the limits of the reference clock, which affects the GPU, CPU, and memory. So, to reach the maximum reference clock, you have to lower all three multipliers and loosen memory timings in the BIOS. Asus' F1A75-V Pro accurately reports the memory and CPU frequencies based on your reference clock. However, it reports the GPU clock assuming the reference is still set to 100 MHz. Leave it at its stock 600 MHz, then, just to be safe.

Finally, we're able to approach memory overclocking. Here's where the elevated reference clock comes in useful. Officially, Llano's highest supported memory speed is 933 MHz (1866 MT/s), meaning you have to push the reference higher to run memory any faster. Know your memory kit's limits going into this, and force the appropriate timings in the BIOS; CPU-Z can help with this:

Our maximum stable memory overclock is 1092 MHz (2184 MT/s) at 1.6 V, achieved with a 117 MHz reference clock. We used 10-10-10-27 2T timings to get there.

With the memory and reference clocks locked in, we tweaked the CPU and GPU clocks to push the limits we discovered earlier. Using a CPU multiplier of 15.5x, the 117 MHz reference clock worked out to a CPU frequency of 3627 MHz. Our GPU speed was less obvious since Asus' BIOS doesn't account for reference clock adjustments. However, experimentation showed that the 800 MHz setting delivered a 936 MHz graphics engine clock.



GPU-Z properly detects our GPU clock. But the memory is reported according to its multiplier, not the actual 1092 MHz rate. Therefore, our final result is: 3627 MHz CPU, 936 MHz GPU, and 1092 MHz (2184 MT/s) memory, all using a 117 MHz reference clock.

Before we move on to testing, it's important to mention the importance of an aftermarket cooler in this application. The A8-3870K’s bundled heat sink and fan are passable at stock settings. However, the combination is pathetically underpowered for coping with the unlocked APU's thermal output using higher voltages.

Using AMD's stock cooler, temperatures quickly reached 70 degrees, at which point the APU would throttle back. Cooler Master's Hyper TX3 did a much better job, preventing throttling.

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Top Comments
  • 22 Hide
    buzznut , August 8, 2012 5:01 AM
    This is pretty cool, this addresses most of the questions I would have about gaming with a LLano part. But it seems Trinity is right around the corner so I would still have reservations about recommending it. Except for the fact I just saw one of these quads for $90 at the egg, which does make a compelling case for folks on a tight budget.
  • 13 Hide
    EzioAs , August 8, 2012 5:02 AM
    Interesting read. Can't wait to see how much of an improvement the desktop Trinity APU brings seeing Llano is better than what I imagine it would be
Other Comments
  • 22 Hide
    buzznut , August 8, 2012 5:01 AM
    This is pretty cool, this addresses most of the questions I would have about gaming with a LLano part. But it seems Trinity is right around the corner so I would still have reservations about recommending it. Except for the fact I just saw one of these quads for $90 at the egg, which does make a compelling case for folks on a tight budget.
  • 13 Hide
    EzioAs , August 8, 2012 5:02 AM
    Interesting read. Can't wait to see how much of an improvement the desktop Trinity APU brings seeing Llano is better than what I imagine it would be
  • 9 Hide
    esrever , August 8, 2012 5:43 AM
    Don is the best!
  • 4 Hide
    peroludiarom , August 8, 2012 5:57 AM
    Hi Don, you have wrote great article!
    I have just one question - do you try to overclock the memory controller as well, because its not mentioned in the article? Thanks in advance
  • -1 Hide
    mayankleoboy1 , August 8, 2012 6:03 AM
    Llano is great, but i am waiting for the die-shrink to reduce power and heat.
  • -6 Hide
    Anonymous , August 8, 2012 6:06 AM
    Wife's pentium intel g620 and amd 7750 on budget board and 8 gb budget ram .....only pulls 150 watts max !!!!!!!!lcost less and performs much better. Apu is a epic idea, alas still useless maybe trinity will save the day. Until then the hype and misleading performance promises will still make them money.
  • 2 Hide
    Fokissed , August 8, 2012 7:27 AM
    On page 2 there is a reference to hwbot.com, which seemingly doesn't exist anymore.

    [EDIT BY CLEEVE] Thanks for catching that, fixed to hwbot.org! [/EDIT]
  • 6 Hide
    freggo , August 8, 2012 8:08 AM
    FokissedOn page 2 there is a reference to hwbot.com, which seemingly doesn't exist anymore.


    Makes you wonder how old the article is that a dead domain link made it into the text :) 
  • 7 Hide
    csbeer , August 8, 2012 8:13 AM
    "So, we installed it (6670) in the overclocked system and disengaged its on-die GPU."

    I don't get why all these major sites don't test the dual graphics nature of the asymetrical xfire that Llano supports? Marry that APU with a 6570 or 6670 for maximum performance, that's the whole point of the Llano experience imo! I have a Llano notebook and am so hungry for info on other's experiments and results with the APU+DGPU.
  • 2 Hide
    biggerbooger , August 8, 2012 9:12 AM
    Excuse the noob question, but if you had say 2 x 4gb sticks rather than 2 x 2 and you put on a corsair H40 contained water cooler for example could you get much better OC performance? This is looking like a viable option.
  • -4 Hide
    serendipiti , August 8, 2012 9:13 AM
    Good article, a bit late (and excuse my paranoia, but having AMD stopped trinity just to end selling A8s in stock makes me think this article comes as an ad...)

    Snow85Wife's pentium intel g620 and amd 7750 on budget board and 8 gb budget ram .....only pulls 150 watts max !!!!!!!!lcost less and performs much better. Apu is a epic idea, alas still useless maybe trinity will save the day. Until then the hype and misleading performance promises will still make them money.


    I don't think it is fair to compare. OK, both are products on the market, but it's not fair. g620 is in fact a marketing item, is a modern intel processor capped down... I would better compare Phenom II + 6670, but comparing AMD and Intel it is not a fair comparison for the APU concept. I don't mean your buying decision should take into account g620...

    Moore's law takes us there: it makes no sense a 32 core cpu on a desktop PC by now, but it makes a lot of sense having a SoC, and getting the desktop PC fit your palm...

    The first APU attempts show lot of binding to memory performance... so 3 / 4 channel architectures should improve a lot the result, the problem is that 2 more channels mean lots of pins on the socket, which rise costs...

    csbeer"So, we installed it (6670) in the overclocked system and disengaged its on-die GPU."I don't get why all these major sites don't test the dual graphics nature of the asymetrical xfire that Llano supports? Marry that APU with a 6570 or 6670 for maximum performance, that's the whole point of the Llano experience imo! I have a Llano notebook and am so hungry for info on other's experiments and results with the APU+DGPU.


    I think the first benchmarks tested that combination...
  • 3 Hide
    vitornob , August 8, 2012 10:08 AM
    serendipitiGood article, a bit late (and excuse my paranoia, but having AMD stopped trinity just to end selling A8s in stock makes me think this article comes as an ad...)I don't think it is fair to compare. OK, both are products on the market, but it's not fair. g620 is in fact a marketing item, is a modern intel processor capped down... I would better compare Phenom II + 6670, but comparing AMD and Intel it is not a fair comparison for the APU concept. I don't mean your buying decision should take into account g620...Moore's law takes us there: it makes no sense a 32 core cpu on a desktop PC by now, but it makes a lot of sense having a SoC, and getting the desktop PC fit your palm... The first APU attempts show lot of binding to memory performance... so 3 / 4 channel architectures should improve a lot the result, the problem is that 2 more channels mean lots of pins on the socket, which rise costs... I think the first benchmarks tested that combination...


    Don't see how this is an unfair comparative. (A8-3870k vs G620 + HD7750)
    Both will serve as CPU, both will serve as GPU, both are in the market. In the PC components market we should look for 3 mainly caracteristics:
    1- Performance on the softwares you use (this include reability and warranty)
    2- Cost of the parts
    3- And a few years to now, energy usage

    If Snow85 is right in his statements, we have the combo g620 + HD7750 being, cheaper, faster and using less energy.
    So.. where's the unfair here? Doesn't both in the same market, being sold for the same people that looks for components?
  • 3 Hide
    A Bad Day , August 8, 2012 11:01 AM
    *Looks at AMD Trinity*

    *Notices that the laptop has a 1066 MHz memory with 9-9-9-x timing*


    Hey manufacturer, why not get a cheaper Trinity and spend a little more on a 1600 or 1866 MHz memory? Oh wait, marketing.
  • 1 Hide
    Lutfij , August 8, 2012 11:16 AM
    good read.
  • 3 Hide
    Onus , August 8, 2012 12:51 PM
    Interesting exercise, especially for those who like to play with their hardware. For those wanting to play on their hardware, there are better choices. I used to be in the first group, but now I'm in the second, although some of the tips here are certainly useful.
    I also thought it was funny how the pic of the CM cooler showed it with the Intel pushpins, not the AMD FM1 mounting bracket.
  • 3 Hide
    gondor , August 8, 2012 1:23 PM
    mayankleoboy1Llano is great, but i am waiting for the die-shrink to reduce power and heat.


    LOL !? Llano *is* a die shrink of K10.5 CPU architecture (formerly at 45 nm) and VLIW5 GPU architecture formerly at 40 nm) down to 32 nm. There aren't going to be any more K10.5 die shrinks, it's a dead architecture for the time being.
  • 5 Hide
    tului , August 8, 2012 1:38 PM
    Snow85Wife's pentium intel g620 and amd 7750 on budget board and 8 gb budget ram .....only pulls 150 watts max !!!!!!!!lcost less and performs much better. Apu is a epic idea, alas still useless maybe trinity will save the day. Until then the hype and misleading performance promises will still make them money.

    In a laptop, where you can't pop in discrete graphics, it is another story. You can easily get a $500 system that can game nearly as well as some $1000 systems(especially the ones with crap Intel HD 3000/4000 crap). If I'm paying $1000+ for a laptop, it'd better have a discrete GPU. At $500 and below, the APU is a great price in that form factor.

    You are right on the desktop though, where you can get much higher per core and per watt performance for x86 out of Intel and just slap in a $80 GPU if or when you need to take graphics up a notch.
  • -1 Hide
    beavermml , August 8, 2012 1:48 PM
    this APU is very good on the laptop.. but can we OCed on laptop?
  • -2 Hide
    serendipiti , August 8, 2012 1:54 PM
    vitornobDon't see how this is an unfair comparative. (A8-3870k vs G620 + HD7750)Both will serve as CPU, both will serve as GPU, both are in the market. In the PC components market we should look for 3 mainly caracteristics: 1- Performance on the softwares you use (this include reability and warranty)2- Cost of the parts3- And a few years to now, energy usageIf Snow85 is right in his statements, we have the combo g620 + HD7750 being, cheaper, faster and using less energy.So.. where's the unfair here? Doesn't both in the same market, being sold for the same people that looks for components?


    It's unfair if you want to test about the APU concept. it's about asking if it makes sense to integrate the GPU with the CPU to get an APU...
    My point of view it is not about to compare products to perform a purchase decision. Making a purchase decision has to do with the concrete situation you are dealing with (and here, every case may be a different one, with different things to look at. Anyway, comparing the energy usage on such a heavily overclocked-overvolted chip is useless, without OC, the A8 is hard to beat on energy usage...)
    My point of view is about trends and comparing technology... For this reason I talked about a 32 core CPU vs SoC and their uses in the current days.
  • 3 Hide
    vitornob , August 8, 2012 2:02 PM
    serendipitiIt's unfair if you want to test about the APU concept. it's about asking if it makes sense to integrate the GPU with the CPU to get an APU... My point of view it is not about to compare products to perform a purchase decision. Making a purchase decision has to do with the concrete situation you are dealing with (and here, every case may be a different one, with different things to look at. Anyway, comparing the energy usage on such a heavily overclocked-overvolted chip is useless, without OC, the A8 is hard to beat on energy usage...)My point of view is about trends and comparing technology... For this reason I talked about a 32 core CPU vs SoC and their uses in the current days.


    Now sir I agree 100%.. trend by trend, AMD APUs are unique
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