Clevo P750ZM: Overclocking Power Requirements

Increasing performance though overclocking will always increase power draw (all other variables being the same), which is part of the concern with overclocking notebooks. On a desktop where you can easily upgrade the power supply and cooling, there are ways to deal with the higher power requirements and increased heat. With a notebook, you’ll want something with a good amount of headroom just to be safe. Thankfully, the P750ZM provides just what we need.

System Power Draw

Typically when overclocking components, there’s a point where the power (voltage) requirements start to increase rapidly for increasingly small performance improvements. Our two overclocking targets represent about a 10% and 20% overclock of the GPU core, and both increase the power requirements. However, the aggressive overclock uses almost 20% more power than the moderate overclock on average, which in turn uses a bit less than 10% more power than the stock clocks. Overall, we’re increasing the power draw by nearly 30% for a 20% increase in performance.

Keep in mind that the higher power draw when overclocked isn’t just coming from the GPU – the CPU will end up working harder to feed the faster GPU, so many of the components in the system will use more power. Still, the majority of the power is almost certainly being funneled into the GTX 980M.

The scaling of performance vs. power with our aggressive overclock is actually not too shabby, but it does raise a concern. When it comes to power, this is going to be one of the limiting factors with overclocking certain notebooks. The P750ZM we received from Eurocom includes the beefier 330W AC adapter, so it’s not a problem, but assuming 85% efficiency on the power bricks the 230W AC adapter would be very close to 100% load. Other laptops (e.g. the Gigabyte P35W v3) come with 180W adapters, which we could easily surpass – never mind the difficulty of cooling an overclocked 980M in a slim chassis.

There’s also the question of temperatures, both internal and external, which is what we’ll look at next.

Clevo P750ZM: Overclocking Performance Clevo P750ZM: Stress Testing
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  • CrazyElf - Friday, March 20, 2015 - link

    To be honest, laptops probably don't have the margins for overclocking that a desktop would.

    For the desktop CPU, it is already pretty hot to begin with. You might be able to knock 15-20C down by delidding that 4790k, much like a desktop. The problem is, with a desktop you can use a giant cooler like the Noctua D15, or water cool. You cannot with a laptop.

    GPUs have similar problems. Large triple slot coolers and water blocks are available - indeed they are made specifically for desktop overclocking. There's no way to do that in a laptop. It just isn't possible.
  • Khenglish - Friday, March 20, 2015 - link

    Did you see the GPU temps? With a 20% overclock it only reached around 77C, which is cooler than many stock coolers on similar desktop cards.

    CPU temps are bad though. I think the problem is that clevo went with a combined GPU/CPU heatsink for this laptop, which is something they have not done before. While this sounds good at first, it makes having good die contact on both CPU and GPU nearly impossible without a large amount of flex in the heatsink, which the P750ZM heatsink does not have.
  • CrazyElf - Friday, March 20, 2015 - link

    Apples to oranges. Maxwell is a pretty cool running chip on desktops too. If you are comparing the 980M to the AMD 290X, then yes, the desktop chips are hot in comparison. But remember, we should be comparing the 980M to a desktop Maxwell, and this is a chip that has 1/4 of the units stripped (so 1536 out of 2048 active) compared to the desktop part, which is already pretty cool running.

    A delid as I said might solve the problem partly like in desktops of the 4790k, but either way, there isn't much OC headroom in that chip even with the delid.

    To be honest, the GT72 is a better choice IMO:

    The CPU runs cooler and the battery life is better, should you ever need it. It is somewhat slower, but not by much. Plus newer versions with an IPS screen are available - I just wish Anandtech had reviewed it with the IPS screen.

    I just wish that instead of overclocking, that a full 2048 version of the 980 were available, running at a lower clockspeed. My wet dream would be the big 3072-Titan X die severely underclocked on a laptop, but that would never happen for various reasons.
  • Khenglish - Saturday, March 21, 2015 - link

    Yeah full 2048 would rock. I am 100% convinced that the only reason it just has 1536 running is so Nvidia can release a fully enabled chip in the future and say they have a new, faster card.
  • JlHADJOE - Saturday, March 21, 2015 - link

    Actually, looking at the combined CPU and GPU temps, it's pretty obvious that system is more or less maxed out thermally.

    The CPU is pegged at 95-99C, and the GPU is similarly pegged at 77C. When the GPU clock is raised is that the CPU clock goes down, so "overclocking" here merely trades CPU clocks for GPU.

    Not that it's a bad idea really, as shown by the game benchmarks, but it does show that there is close to no headroom at all in the Clevo's combined thermals.
  • Hrel - Friday, March 20, 2015 - link

    I think overclocking with today's hardware is stupid, I have no interest in it. I tend to agree with Nvidia on OC.

    However, that doesn't mean they should go so far as to BLOCK people from being able to do it. Ultimately once they've bought it, it's their choice. At least it should be.

    Have OC void the warranty and be done with it. There's no reason to do anything more than that. "You wanna overclock? Fine, do so at your own peril. We wash our hands of you".

    This attitude would bring their position from being the right one for 99.9% of the market to 100%.
  • will54 - Friday, March 20, 2015 - link

    I thought they already voided the warranty on OC's or is it just when you go with a modded vbios that they void the warranty ?
  • Buk Lau - Friday, March 20, 2015 - link

    Nice work Jarred, glad to see authoritative sites like AT starts to acknowledge OC on mobile GPU! Although you still didn't test with USB 3.1 ports on this machine (so you didn't have peripherals available?)... and in the future I would recommend when you are doing stress tests, just run Prime95 and and Furmark instead for maximum heat on the system. Running Prime95 and tombraider at the same time actually reduces CPU load, because floating point calculation requires much higher work load than game physics. That aside you did a fantastic job! Funny when you noted on potential reasons why Nvidia blocked OC, every generation some cards are just rebrands of old cards with a slightly higher clockspeed. So essentially you can get a free upgrade yourself when you do that, and OC damaging the gpu might not as much of a threat if Nvidia is doing it themselves every generation LOL
  • ajc9988 - Friday, March 20, 2015 - link

    I disagree with your choice of tests. Max heat isn't the goal with a laptop UNLESS YOU LITERALLY PUSH THE HEAT ON YOUR MACHINE DAILY FOR ITS INTENDED PURPOSE. I had to change the way I thought about overclocking when I came to a laptop. It isn't about max heat like desktop testing (which now reflecting on it is a little stupid if you never do real world activities that push it like that). You want to test max heat for real world type tests. Anything you may do (x264 for avx encoding, etc. There is a long list of stress tests that fully stress the machine without giving synthetic instruction sets to push the hardware to a heat max.). Also, Furmark and Kombuster are vbios blocked in the premamod bios.
  • JlHADJOE - Saturday, March 21, 2015 - link

    Yipes! Close to 100°C on the CPU. That is insane.

    They should run heatpipes to a round metal plate where you can set a mug somewhere on that thing. Cools the CPU, and keeps your drink warm!

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