The Math Behind GPU Power Consumption And PSUs

Garbage in, garbage out. That's what you get if you don't spend enough time planning and testing your benchmarking methodologies. It's easy to fall victim to this golden rule, since preparation requires a lot of effort, eating into nights and weekends. It has taken me a year to find a solution that I’m really happy with. I’ve gained a lot of insights along the way, and discovered some phenomenon I really didn’t expect.

I originally set out to improve our power consumption measurements for graphics cards. I felt that the usual way of doing this via estimates based on measurements at the power plug just didn’t cut it, and I wanted a way to get more reliable and valid results with some extra effort.

Simple current clamps, multimeters and the first data loggers never quite worked for me. Something was always off, and it got really frustrating when every measurement arrived at a different result. There was some factor I was just not taking into account. But what could it be?

That's exactly what I want to diagnose over the next few pages. Unfortunately, I can’t spare you a certain minimum amount of theory. It’s exactly this knowledge that’s so important if you want to understand why the simple solutions don’t work. Never fear, though. The story won’t be boring or dry, and I’ve boiled down and simplified the subject matter as much as I could.

The measurement setup was systematically changed and improved time and time again in cooperation with our industrial partner. Entire configurations were tested, only to be scrapped again. Firmware was updated, nearly putting us back to square one. All in all, creating this platform was a lot of work on top of my already time-sensitive assignments, especially since everything had to be built in the midst of our normal operation.

All of the effort was really worthwhile, though. And, when it really comes down to it, transparency always beats secrecy. The latter might be good for business, but, in the end, you need to be able to back up your claims, especially if you publish them. This is why I’ll tell you the secret of how we get to the results produced by our measurements. Otherwise, you might just not believe them…

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  • Chazn2
    This article is insane (positive slang)!

    It's got so much detail and it's so interesting. I love it.

    I have an expensive but fairly old 750W PSU, I know it's a good one cos once my computer kept running for a good few seconds after power went out, plus it's lasted this long with some pretty hefty graphics cards in it. I got it at the time cos I had been warned of how important a good PSU is, now I guess we are seeing why.

    Regardless, excellent article.
  • Minish Man
    Awesome article! I learned so much. I guess that this change in graphics card power delivery is why so many cards seem to cause coil whine these days. If they're going to demand so much more of the voltage regulators then need to use higher quality / more of them and wire them up better!

    I have had a similar experience to you living in China and repairing / upgrading my own electric scooter. Very slowly learning, largely in a second language, trying, not understanding why the simple solution doesn't work, relearning, getting frustrated with cheap components not behaving as they should. It's a great experience :D
  • Aereto
    Suffice to say, I am adding PSUs into the high scrutiny and research, especially when PSUs are part of my potentially life-time longevity components.

    The effectiveness of my research is hampered by my current experience and training. My major is not exactly in the engineering field, but covers a greater emphasis on the software side of computers, so hardware-related training and learning may not be covered as intensely.