12 ms·

Intel Blocks Undervolting: The Whole Story

66 points by shaicoleman 4y ago

nottorp 4y ago
[flagged]
empiricus 4y ago
I always use undervolting on laptops: with just a little undervolt, the laptop runs silent instead of constant ventilator noise when staring at a web page. (currently using a ryzen laptop, previously many intel laptops)
- zen_1 4y ago
  How did you undervolt your ryzen laptop? I used to use Throttlestop but it doesn't support newer Ryzens
  - arprocter 4y ago
    There's a utility called AATU, although apparently it might not play nice with anti-cheat stuff
  - empiricus 4y ago
    I use ryzenadj on ubuntu. There seems to be windows version too. It actually modifies the power limits (I reduce them from 45w to 20w), not quite undervolt like intel cpu-s in the past.
- jeffbee 4y ago
  Why don't you just use the normal power controls instead of undervolting?
  - Astronaut3315 4y ago
    Power controls sacrifice performance, whereas undervolting maintains (or improves!) performance with the added risk of instability. Once thoroughly tested, though, undervolting is absolutely the way to go.
    - jeffbee 4y ago
      It's the thoroughness of testing that I doubt.
sandworm101 4y ago
Next feature: SpaceHeater mode. Now your customers in cold climates can reduce their heating needs by running Intel CPUs at extra-high voltages, allowing even seldom used cores to pump out heat as if they were running Edge 24/7. Your customer's software wont be stable, but their electricity bill sure will be.
- jwestbury 4y ago
  Years ago, Puget Systems actually ran some tests on using desktop PCs as space heaters. tl;dr, you can use your desktop as a space heater with identical efficiency to an actual space heater, but with the benefit of computing power to go along with it.
  - Faaak 4y ago
    That's partly what I do, but by running Folding@Home during the day (I have solar panels, and I export a lot of electricity). Free heat + compute capacity science
    - squeaky-clean 4y ago
      I had to stay in a hotel recently where the thermostat wouldn't go above 68f. Left my laptop running a busy park in Planet Zoo on the nightstand. It's not a true space heater but it did warn the room a couple of extra degrees.
  - shagie 4y ago
    There's an over priced "bitcoin space heater" out there that is apparently / unfortunately not a joke.
    - nicolaslem 4y ago
      Two main reasons this is stupid: - Heat pumps - Someone buying such expensive gear will want to run it all the time before it is severely outdated, not only a few months per year.
codedokode 4y ago
It is annoying that since long ago Intel uses lockable registers in CPU and chipset, so that the BIOS can lock them and even administrator cannot change anything. This is a user-hostile behaviour. This is absolutely unnecessary.
haunter 4y ago
First thing I did was on my 13600k was undervolting by -0,150v. The default settings (by the motherboard manufacturer) are not bad per se but basically eating so much power for a small performace increase. After undervolting the power consumption dropped by ~30-40% with a loss of ~5% performance. And temps also down by 10-15C. But tbh same with GPUs as well. RTX 3080. Conservative undervolting (850mv @ 1800-1850Mhz) works on most cards and with the same effect, loss of ~5% performance but power consumption down by ~30-40% + significantly cooler (10-15C) And you could go even lower if you like tinkering + got a good draw on the silicon lottery. Edit: changed to power consumption
- jstanley 4y ago
  How can changing the voltage change the TDP? Isn't the TDP a property of the physical design, not the operating conditions?
  - pixl97 4y ago
    I think in this case it's being used as a measure of thermal performance at "100%" usage at a particular voltage. See the Wikipedia page on this and you'll see in modern processors that TDP is configurable. >TDP specifications for some processors may allow them to work under multiple different power levels, depending on the usage scenario, available cooling capacities and desired power consumption. Technologies that provide such variable TDPs include Intel's configurable TDP (cTDP) and scenario design power (SDP), and AMD's TDP power cap.
  - haunter 4y ago
    Yeah maybe I'm using the wrong term here sorry for that. As far as I know the maximum wattage that the CPU can draw doesn't change by undervolting it. But the power consumption in watts at any given momement drops significantly. Changed the wording.
    - deleted 4y ago
      [deleted]
  - 4y ago
RandomTisk 4y ago
<ConspiracyTheory> Intel is blocking undervolting because, even though it can improve temperatures and increase clock speeds, it can cause the ME and other black box "features" to stop functioning. Someone doesn't want that. </ConspiracyTheory>
- nicolaslem 4y ago
  That is not a conspiracy theory, that is literally what is discussed in the fine article.
  - orangepurple 4y ago
    It is a conspiracy theory. One that is true.
Astronaut3315 4y ago
I recently repurposed an 8th gen desktop as a home server. As a part of the commissioning process I clamped down PL1/PL2 to keep power usage low in its new 24x7 application. A critical part of that was undervolting the CPU to maintain acceptable performance. I guess Intel’s preferred solution would be to swap the CPU (an 8700k) for something like a 35W 8600T. What a waste.
ilyt 4y ago
Huh, Intel is really trying for enthusiasts to not want to touch their products... If it really is security problem all it should be is an option that can be turned off, not mobo manufacturers trying to get around what intel did
deleted 4y ago
[deleted]
Aardwolf 4y ago
Is there any chance AMD might introduce a similar thing, that is, is there some fundamental physical problem about undervolting that applies to all CPU's in the end and inevitably will require all manufacturers to block this eventually, or is this an intel-specific drama, related to intel-only design decisions or marketing?
- PragmaticPulp 4y ago
  > inevitably will require all manufacturers to block this eventually, Intel didn't block it (contrary to the title). They gave vendors the tools to block it to avoid security issues. Undervolting can induce glitches in any CPU, so the vulnerability is technically not unique to Intel. Only the current proof of concepts are limited to Intel. Enthusiast motherboards aren't required to block undervolting. It's a vendor option. If you buy an enthusiast motherboard, it's almost certainly going to leave it enabled.
PragmaticPulp 4y ago
A lot of jumping to conclusions in this thread, but no, Intel did not block undervolting across the board. As the linked post explains, they implemented an option for vendors to block runtime undervolting from the BIOS/motherboard side. This was in response to a published CVE that used undervolting as a way of inducing and exploiting instability in the system: https://plundervolt.com/ https://plundervolt.com/ If you buy an enthusiast motherboard with overclocking and voltage adjustment controls, it's extremely unlikely that the motherboard vendor would choose to block undervolting for you. Being able to adjust and tweak things is the whole point of premium motherboards. It would be illogical for them to choose to block a popular feature. On the other hand, if you're using an OEM motherboard from some vendor that takes security seriously, I wouldn't be surprised to see undervolting blocked for security reasons. This seems logical, because not many people are buying OEM Dell workstations so they can go in and tweak every last detail in the BIOS. IMO, Intel did the right thing here. They responded to a CVE by providing an option for vendors to enable that addresses the issue. Meanwhile, enthusiasts can continue doing what they want. Seems like much ado about nothing. There's even a fantastic timeline and explanation from an Intel community member as the top comment on Reddit: https://old.reddit.com/r/intel/comments/10slejm/intel_blocks_undervolting_the_whole_story/j73ge9a/ https://old.reddit.com/r/intel/comments/10slejm/intel_blocks...
- saurik 4y ago
  The security issue you linked to was not something that provided the owner of the computer security but instead provides security for third-parties against the owner of the computer and their meddling notions of privacy or transparency. It is totally fine to make an argument for why they made a rational decision here, and you can even argue it has something to do with benefits to the user--though I am unsure I've ever heard of, say, a movie company banning computers from HQ video over stuff like this--but using the term "security" is disingenuous as like, I read your comment and seriously upvoted it as "sounds reasonable" until I decided to go and actually read about this fascinating exploit... and then I was all "oh :/".
  - FreakLegion 4y ago
    You're referring to Plundervolt? At a glance it could be used to extract private keys from e.g. FIDO2 platform authenticators. I don't know how widespread SGX use is at this point, but it already shows up in common Windows Hello flows, 1Password, some crypto wallets, and will probably be fairly common in passkey implementations. Based on that I'd say it's fair to disable undervolting for security reasons.

66 points by shaicoleman 4y ago

[flagged]

I always use undervolting on laptops: with just a little undervolt, the laptop runs silent instead of constant ventilator noise when staring at a web page. (currently using a ryzen laptop, previously many intel laptops)

zen_1 4y ago
How did you undervolt your ryzen laptop? I used to use Throttlestop but it doesn't support newer Ryzens
- arprocter 4y ago
  There's a utility called AATU, although apparently it might not play nice with anti-cheat stuff
- empiricus 4y ago
  I use ryzenadj on ubuntu. There seems to be windows version too. It actually modifies the power limits (I reduce them from 45w to 20w), not quite undervolt like intel cpu-s in the past.
jeffbee 4y ago
Why don't you just use the normal power controls instead of undervolting?
- Astronaut3315 4y ago
  Power controls sacrifice performance, whereas undervolting maintains (or improves!) performance with the added risk of instability. Once thoroughly tested, though, undervolting is absolutely the way to go.
  - jeffbee 4y ago
    It's the thoroughness of testing that I doubt.

sandworm101 4y ago

Next feature: SpaceHeater mode. Now your customers in cold climates can reduce their heating needs by running Intel CPUs at extra-high voltages, allowing even seldom used cores to pump out heat as if they were running Edge 24/7. Your customer's software wont be stable, but their electricity bill sure will be.

jwestbury 4y ago
Years ago, Puget Systems actually ran some tests on using desktop PCs as space heaters. tl;dr, you can use your desktop as a space heater with identical efficiency to an actual space heater, but with the benefit of computing power to go along with it.
- Faaak 4y ago
  That's partly what I do, but by running Folding@Home during the day (I have solar panels, and I export a lot of electricity). Free heat + compute capacity science
  - squeaky-clean 4y ago
    I had to stay in a hotel recently where the thermostat wouldn't go above 68f. Left my laptop running a busy park in Planet Zoo on the nightstand. It's not a true space heater but it did warn the room a couple of extra degrees.
- shagie 4y ago
  There's an over priced "bitcoin space heater" out there that is apparently / unfortunately not a joke.
  - nicolaslem 4y ago
    Two main reasons this is stupid: - Heat pumps - Someone buying such expensive gear will want to run it all the time before it is severely outdated, not only a few months per year.

codedokode 4y ago

It is annoying that since long ago Intel uses lockable registers in CPU and chipset, so that the BIOS can lock them and even administrator cannot change anything. This is a user-hostile behaviour. This is absolutely unnecessary.

haunter 4y ago

First thing I did was on my 13600k was undervolting by -0,150v. The default settings (by the motherboard manufacturer) are not bad per se but basically eating so much power for a small performace increase. After undervolting the power consumption dropped by ~30-40% with a loss of ~5% performance. And temps also down by 10-15C. But tbh same with GPUs as well. RTX 3080. Conservative undervolting (850mv @ 1800-1850Mhz) works on most cards and with the same effect, loss of ~5% performance but power consumption down by ~30-40% + significantly cooler (10-15C) And you could go even lower if you like tinkering + got a good draw on the silicon lottery. Edit: changed to power consumption

jstanley 4y ago
How can changing the voltage change the TDP? Isn't the TDP a property of the physical design, not the operating conditions?
- pixl97 4y ago
  I think in this case it's being used as a measure of thermal performance at "100%" usage at a particular voltage. See the Wikipedia page on this and you'll see in modern processors that TDP is configurable. >TDP specifications for some processors may allow them to work under multiple different power levels, depending on the usage scenario, available cooling capacities and desired power consumption. Technologies that provide such variable TDPs include Intel's configurable TDP (cTDP) and scenario design power (SDP), and AMD's TDP power cap.
- haunter 4y ago
  Yeah maybe I'm using the wrong term here sorry for that. As far as I know the maximum wattage that the CPU can draw doesn't change by undervolting it. But the power consumption in watts at any given momement drops significantly. Changed the wording.
  - deleted 4y ago
    [deleted]
- 4y ago

RandomTisk 4y ago

<ConspiracyTheory> Intel is blocking undervolting because, even though it can improve temperatures and increase clock speeds, it can cause the ME and other black box "features" to stop functioning. Someone doesn't want that. </ConspiracyTheory>

nicolaslem 4y ago
That is not a conspiracy theory, that is literally what is discussed in the fine article.
- orangepurple 4y ago
  It is a conspiracy theory. One that is true.

Astronaut3315 4y ago

I recently repurposed an 8th gen desktop as a home server. As a part of the commissioning process I clamped down PL1/PL2 to keep power usage low in its new 24x7 application. A critical part of that was undervolting the CPU to maintain acceptable performance. I guess Intel’s preferred solution would be to swap the CPU (an 8700k) for something like a 35W 8600T. What a waste.

ilyt 4y ago

Huh, Intel is really trying for enthusiasts to not want to touch their products... If it really is security problem all it should be is an option that can be turned off, not mobo manufacturers trying to get around what intel did

deleted 4y ago

[deleted]

Aardwolf 4y ago

Is there any chance AMD might introduce a similar thing, that is, is there some fundamental physical problem about undervolting that applies to all CPU's in the end and inevitably will require all manufacturers to block this eventually, or is this an intel-specific drama, related to intel-only design decisions or marketing?

PragmaticPulp 4y ago
> inevitably will require all manufacturers to block this eventually, Intel didn't block it (contrary to the title). They gave vendors the tools to block it to avoid security issues. Undervolting can induce glitches in any CPU, so the vulnerability is technically not unique to Intel. Only the current proof of concepts are limited to Intel. Enthusiast motherboards aren't required to block undervolting. It's a vendor option. If you buy an enthusiast motherboard, it's almost certainly going to leave it enabled.

PragmaticPulp 4y ago

A lot of jumping to conclusions in this thread, but no, Intel did not block undervolting across the board. As the linked post explains, they implemented an option for vendors to block runtime undervolting from the BIOS/motherboard side. This was in response to a published CVE that used undervolting as a way of inducing and exploiting instability in the system: https://plundervolt.com/ https://plundervolt.com/ If you buy an enthusiast motherboard with overclocking and voltage adjustment controls, it's extremely unlikely that the motherboard vendor would choose to block undervolting for you. Being able to adjust and tweak things is the whole point of premium motherboards. It would be illogical for them to choose to block a popular feature. On the other hand, if you're using an OEM motherboard from some vendor that takes security seriously, I wouldn't be surprised to see undervolting blocked for security reasons. This seems logical, because not many people are buying OEM Dell workstations so they can go in and tweak every last detail in the BIOS. IMO, Intel did the right thing here. They responded to a CVE by providing an option for vendors to enable that addresses the issue. Meanwhile, enthusiasts can continue doing what they want. Seems like much ado about nothing. There's even a fantastic timeline and explanation from an Intel community member as the top comment on Reddit: https://old.reddit.com/r/intel/comments/10slejm/intel_blocks_undervolting_the_whole_story/j73ge9a/ https://old.reddit.com/r/intel/comments/10slejm/intel_blocks...

saurik 4y ago
The security issue you linked to was not something that provided the owner of the computer security but instead provides security for third-parties against the owner of the computer and their meddling notions of privacy or transparency. It is totally fine to make an argument for why they made a rational decision here, and you can even argue it has something to do with benefits to the user--though I am unsure I've ever heard of, say, a movie company banning computers from HQ video over stuff like this--but using the term "security" is disingenuous as like, I read your comment and seriously upvoted it as "sounds reasonable" until I decided to go and actually read about this fascinating exploit... and then I was all "oh :/".
- FreakLegion 4y ago
  You're referring to Plundervolt? At a glance it could be used to extract private keys from e.g. FIDO2 platform authenticators. I don't know how widespread SGX use is at this point, but it already shows up in common Windows Hello flows, 1Password, some crypto wallets, and will probably be fairly common in passkey implementations. Based on that I'd say it's fair to disable undervolting for security reasons.