4 ms·

CPUs are very good about protecting themselves, but I'm shocked no one noticed that they took many hours to boot up or to do anything at all.

Wowfunhappy 2y ago
Sure, but in this case, I would have expected "protecting itself" to mean "shutting down." Can a server CPU—or any x86 cpu, for that matter—actually downclock itself enough to run without any sort of cooler?
- eep_social 2y ago
  486s were sometimes passively cooled. A room full of hardware replaced by a very early virtualization setup lines up reasonably well. I did one of these in the early naughts. Something like half a rack of old pentium 2-3 era boxes running non-prod — back office, network share storage, dev, staging — to a single beefy server running some flavor of vmware. We had all the older gen hardware for isolation and convenience, not because we needed the compute so I specced a “big” box that could hold a lot of storage (for the time) and performance was a non-issue. I think I also saved a lot on Microsoft licensing which made budget for the hardware.
  - tonyarkles 2y ago
    In the early 2000s we had a mail server running on an old recycled Cyrix 5x86. When we had to move offices someone knocked down the wall next to the server but as it turned out the Ethernet cable was stapled to the wall and the machine went flying. Whatever, pack it up and move to the new office, plug it back in and it works fine. About a year later we were rearranging some stuff and someone powered it off and picked it up to move it… and heard a rattle inside. Pop the cover off and the CPU cooler is sitting in the bottom of the case and the CPU is just sitting there naked. Had absolutely no problem running without the fan at all. We clipped it back on anyway just to be safe :)
- MobiusHorizons 2y ago
  I believe they can, although you’d probably violate the warranty.
- stordoff 2y ago
  There are a few videos on YouTube showing CPUs running without a heatsink. I haven't watched them to see how long they can run for, or if any BIOS changes were needed (I noticed the first mentions a lower voltage needs to be set to boot into Windows), but it seems possible at least. There are also comments that claim to have done this (the oldest I saw was a Q8200, and someone said a 3000G could be run indefinitely without a heatsink). https://www.youtube.com/watch?v=tU9yjwMlbRI https://www.youtube.com/watch?v=tU9yjwMlbRI (Ryzen 3000) https://www.youtube.com/watch?v=ycIF1NDkW6M https://www.youtube.com/watch?v=ycIF1NDkW6M (Pentium G5400)
- hollerith 2y ago
  I'm writing this on a passively-cooled mini PC with Intel N100 CPU. (It has only E cores, no P cores.)
  - Wowfunhappy 2y ago
    But passively cooled doesn't mean no cooler! Or does the CPU literally not have a heatsink?
    - hollerith 2y ago
      It has a heat sink.
      - Wowfunhappy 2y ago
        Right, so that's very different than covering the CPU with tape and nothing else! I frankly don't believe GP's story, I think GP must be misremembering this detail.
        hollerith 2y ago
        Yeah, I didnt read the OP before commenting, wasting everyone's time...
- dtgriscom 2y ago
  I've heart that Intel CPUs can (often?) function (sloooowly?) without a cooler, while AMD CPUs will burn up. Perhaps the latter's temperature sensors aren't necessarily close to the major sources of heat, so the chip burns up before it notices that it's burning up. (And a cooler spreads the heat out so that the temp sensors see the real temperature.)
- razakel 2y ago
  I've seen one downclock to 300MHz after the heatsink fan failed.
- camtarn 2y ago
  I was playing Cities: Skylines on my old desktop PC a couple of years ago and the frame rate was really low. Windows was running sluggishly but mostly fine. I downloaded CpuZ to figure out what was going on with Skylines, and noticed that the core frequency was way lower than it should have been. I poked around in software for a while but couldn't figure out what was going on ... until I opened my case and realised that my CPU heatsink was dangling off the CPU, the top mounting pins having come loose. So, yep, CPUs - at least 2014-vintage Intel Core i5s - can run surprisingly well without cooling!
TacticalCoder 2y ago
> CPUs are very good about protecting themselves, but I'm shocked no one noticed that they took many hours to boot up or to do anything at all. Why would they take hours? Something something about energy consumption (and heat) growing to the square of the clock speed. You take a server that can go to, say, 3.2 Ghz and limit it to, say, 0.8 Ghz, it's going to be cool to the touch. And at 25% the speed, something taking ms or seconds, won't suddenly take hours. That's why nobody noticed: because they didn't take hours neither to boot nor to do something.
- blitzar 2y ago
  Guessing they got a 100x speedup when they moved to the cloud.
- cesarb 2y ago
  > Why would they take hours? Thermal throttling. I have personal experience with that: once I received a laptop which was missing the four screws holding the heatsink. It took over half an hour trying to boot Windows before powering down due to overheating. Since I'm not used to Windows, I thought it being very slow (on the first boot, which sets things up) might be normal, but suddenly powering down certainly wasn't, and the BIOS event log pointed to the culprit. The issue is that AFAIK it does not reduce the clock rate; it runs at the normal full clock rate, then when it detects the temperature went over the limit, it pauses the CPU for a while to let it cool down. With a missing CPU fan, that might be enough, but it wasn't enough with the heatsink detached. > That's why nobody noticed: because they didn't take hours neither to boot nor to do something. It's normal for servers to take a while to boot (before even getting to the operating system).
  - camtarn 2y ago
    Probably depends on the CPU. When my 2014-era Core i5's heatsink fell off (see comment above) I could see the CPU clocks actually reducing.
  - kadoban 2y ago
    > The issue is that AFAIK it does not reduce the clock rate; it runs at the normal full clock rate, then when it detects the temperature went over the limit, it pauses the CPU for a while to let it cool down. I'm 99% confident that that is not a thing, pausing the cpu. The closest thing that exists is sleep/suspend/hibernate, but those don't work like that (on temperature triggers). Other than those, if the machine is on: the cpu is always doing _something_.
eternityforest 2y ago
The thermal mass may have been enough to get through a lot of the boot, then by the time it's running maybe they're so lightly loaded nobody noticed. Some people really like dedicated single function hardware, they might have been putting a micro service on each one

Wowfunhappy 2y ago

Sure, but in this case, I would have expected "protecting itself" to mean "shutting down." Can a server CPU—or any x86 cpu, for that matter—actually downclock itself enough to run without any sort of cooler?

eep_social 2y ago
486s were sometimes passively cooled. A room full of hardware replaced by a very early virtualization setup lines up reasonably well. I did one of these in the early naughts. Something like half a rack of old pentium 2-3 era boxes running non-prod — back office, network share storage, dev, staging — to a single beefy server running some flavor of vmware. We had all the older gen hardware for isolation and convenience, not because we needed the compute so I specced a “big” box that could hold a lot of storage (for the time) and performance was a non-issue. I think I also saved a lot on Microsoft licensing which made budget for the hardware.
- tonyarkles 2y ago
  In the early 2000s we had a mail server running on an old recycled Cyrix 5x86. When we had to move offices someone knocked down the wall next to the server but as it turned out the Ethernet cable was stapled to the wall and the machine went flying. Whatever, pack it up and move to the new office, plug it back in and it works fine. About a year later we were rearranging some stuff and someone powered it off and picked it up to move it… and heard a rattle inside. Pop the cover off and the CPU cooler is sitting in the bottom of the case and the CPU is just sitting there naked. Had absolutely no problem running without the fan at all. We clipped it back on anyway just to be safe :)
MobiusHorizons 2y ago
I believe they can, although you’d probably violate the warranty.
stordoff 2y ago
There are a few videos on YouTube showing CPUs running without a heatsink. I haven't watched them to see how long they can run for, or if any BIOS changes were needed (I noticed the first mentions a lower voltage needs to be set to boot into Windows), but it seems possible at least. There are also comments that claim to have done this (the oldest I saw was a Q8200, and someone said a 3000G could be run indefinitely without a heatsink). https://www.youtube.com/watch?v=tU9yjwMlbRI https://www.youtube.com/watch?v=tU9yjwMlbRI (Ryzen 3000) https://www.youtube.com/watch?v=ycIF1NDkW6M https://www.youtube.com/watch?v=ycIF1NDkW6M (Pentium G5400)
hollerith 2y ago
I'm writing this on a passively-cooled mini PC with Intel N100 CPU. (It has only E cores, no P cores.)
- Wowfunhappy 2y ago
  But passively cooled doesn't mean no cooler! Or does the CPU literally not have a heatsink?
  - hollerith 2y ago
    It has a heat sink.
    - Wowfunhappy 2y ago
      Right, so that's very different than covering the CPU with tape and nothing else! I frankly don't believe GP's story, I think GP must be misremembering this detail.
      - hollerith 2y ago
        Yeah, I didnt read the OP before commenting, wasting everyone's time...
dtgriscom 2y ago
I've heart that Intel CPUs can (often?) function (sloooowly?) without a cooler, while AMD CPUs will burn up. Perhaps the latter's temperature sensors aren't necessarily close to the major sources of heat, so the chip burns up before it notices that it's burning up. (And a cooler spreads the heat out so that the temp sensors see the real temperature.)
razakel 2y ago
I've seen one downclock to 300MHz after the heatsink fan failed.
camtarn 2y ago
I was playing Cities: Skylines on my old desktop PC a couple of years ago and the frame rate was really low. Windows was running sluggishly but mostly fine. I downloaded CpuZ to figure out what was going on with Skylines, and noticed that the core frequency was way lower than it should have been. I poked around in software for a while but couldn't figure out what was going on ... until I opened my case and realised that my CPU heatsink was dangling off the CPU, the top mounting pins having come loose. So, yep, CPUs - at least 2014-vintage Intel Core i5s - can run surprisingly well without cooling!

TacticalCoder 2y ago

> CPUs are very good about protecting themselves, but I'm shocked no one noticed that they took many hours to boot up or to do anything at all. Why would they take hours? Something something about energy consumption (and heat) growing to the square of the clock speed. You take a server that can go to, say, 3.2 Ghz and limit it to, say, 0.8 Ghz, it's going to be cool to the touch. And at 25% the speed, something taking ms or seconds, won't suddenly take hours. That's why nobody noticed: because they didn't take hours neither to boot nor to do something.

blitzar 2y ago
Guessing they got a 100x speedup when they moved to the cloud.
cesarb 2y ago
> Why would they take hours? Thermal throttling. I have personal experience with that: once I received a laptop which was missing the four screws holding the heatsink. It took over half an hour trying to boot Windows before powering down due to overheating. Since I'm not used to Windows, I thought it being very slow (on the first boot, which sets things up) might be normal, but suddenly powering down certainly wasn't, and the BIOS event log pointed to the culprit. The issue is that AFAIK it does not reduce the clock rate; it runs at the normal full clock rate, then when it detects the temperature went over the limit, it pauses the CPU for a while to let it cool down. With a missing CPU fan, that might be enough, but it wasn't enough with the heatsink detached. > That's why nobody noticed: because they didn't take hours neither to boot nor to do something. It's normal for servers to take a while to boot (before even getting to the operating system).
- camtarn 2y ago
  Probably depends on the CPU. When my 2014-era Core i5's heatsink fell off (see comment above) I could see the CPU clocks actually reducing.
- kadoban 2y ago
  > The issue is that AFAIK it does not reduce the clock rate; it runs at the normal full clock rate, then when it detects the temperature went over the limit, it pauses the CPU for a while to let it cool down. I'm 99% confident that that is not a thing, pausing the cpu. The closest thing that exists is sleep/suspend/hibernate, but those don't work like that (on temperature triggers). Other than those, if the machine is on: the cpu is always doing _something_.

eternityforest 2y ago

The thermal mass may have been enough to get through a lot of the boot, then by the time it's running maybe they're so lightly loaded nobody noticed. Some people really like dedicated single function hardware, they might have been putting a micro service on each one