6 ms·

Someone did a power analysis of the 13900K https://www.reddit.com/r/hardware/comments/10bna5r/13900k_power_scaling_analysis/ https://www.reddit.com/r/hardware/c

by chx 4y ago

Someone did a power analysis of the 13900K https://www.reddit.com/r/hardware/comments/10bna5r/13900k_power_scaling_analysis/ https://www.reddit.com/r/hardware/comments/10bna5r/13900k_po... and the CPU scales very well with power limit up to around 100W where the returns are rapidly diminishing.

jeffbee 4y ago
100W is also my observed sweet spot on C++ project build times. At 100W I got the minimum build time. At higher limits the cpu draws more power indeed but the build takes just as long.
- moffkalast 4y ago
  It still feels insane that a CPU can draw that much power. I mean that's like over 8 amps at 12 volts for doing... well nothing really. It's 100 watts of pointless resistance losses. Something that could've powered like half of an electric scooter at top speed. And GPUs are like 3-4 times worse.
  - jeffbee 4y ago
    With its 8 amps—more like 80A at typical core voltages—it retires potentially hundreds of billions of instructions per second. That is a long way from nothing in my book.
    - moffkalast 4y ago
      Well sure, but would you count that as actual "work" in terms of physics? I think not, at least not to any degree that should be notable. There's no practical work being done in a CPU, it's just throwing away charge so it can redirect it around and do some calculations in the process, like a river flowing downhill with some mechanical logic gates in the stream.
      - kzrdude 4y ago
        Maybe we'll look back at this and have a 100x improvement in energy use. I'm not sure we should be surprised - changes cost energy. Lots of clock pulses and lots of transistors change state at GHz frequency.
        moffkalast 4y ago
        The main problem I guess is that x64/x86 aren't designed for power efficiency as much as just pure speed. RISC does a lot better, and biological computers are on a few orders of magnitude more efficient. So there's definitely a lot of room for improvement.
      - B1FF_PSUVM 4y ago
        Incandescent light bulbs ...
  - imtringued 4y ago
    It's worse than you think. During switching both the n and p transistors in a cmos circuit are open simultaneously for a brief period of time. During this time you are essentially shorting your power supply to ground!
    - moffkalast 4y ago
      "Dear god." "There's more." "NO."
metadat 4y ago
The linked graphs paint a really clear picture, thank you for sharing.

by chx 4y ago

jeffbee 4y ago

100W is also my observed sweet spot on C++ project build times. At 100W I got the minimum build time. At higher limits the cpu draws more power indeed but the build takes just as long.

moffkalast 4y ago
It still feels insane that a CPU can draw that much power. I mean that's like over 8 amps at 12 volts for doing... well nothing really. It's 100 watts of pointless resistance losses. Something that could've powered like half of an electric scooter at top speed. And GPUs are like 3-4 times worse.
- jeffbee 4y ago
  With its 8 amps—more like 80A at typical core voltages—it retires potentially hundreds of billions of instructions per second. That is a long way from nothing in my book.
  - moffkalast 4y ago
    Well sure, but would you count that as actual "work" in terms of physics? I think not, at least not to any degree that should be notable. There's no practical work being done in a CPU, it's just throwing away charge so it can redirect it around and do some calculations in the process, like a river flowing downhill with some mechanical logic gates in the stream.
    - kzrdude 4y ago
      Maybe we'll look back at this and have a 100x improvement in energy use. I'm not sure we should be surprised - changes cost energy. Lots of clock pulses and lots of transistors change state at GHz frequency.
      - moffkalast 4y ago
        The main problem I guess is that x64/x86 aren't designed for power efficiency as much as just pure speed. RISC does a lot better, and biological computers are on a few orders of magnitude more efficient. So there's definitely a lot of room for improvement.
    - B1FF_PSUVM 4y ago
      Incandescent light bulbs ...
- imtringued 4y ago
  It's worse than you think. During switching both the n and p transistors in a cmos circuit are open simultaneously for a brief period of time. During this time you are essentially shorting your power supply to ground!
  - moffkalast 4y ago
    "Dear god." "There's more." "NO."

metadat 4y ago

The linked graphs paint a really clear picture, thank you for sharing.