4 ms·

Can this be fixed by removing the efuse or having a custom firmware?

MPSimmons 2y ago
e-fuses (https://en.wikipedia.org/wiki/EFuse https://en.wikipedia.org/wiki/EFuse) are typically etched into the silicon as an exactly-once operation, meant to irrevocably set a configuration. Some devices, for instance, have an e-fuse that makes it impossible to change cryptographic trust signatures after the e-fuse has been blown.
- sabareesh 2y ago
  That's intriguing; one might assume that a key feature of eFuse would be the ability to reset easily. But I guess it could be implemented without it
  - wmf 2y ago
    No, the essence of a fuse is that it can never be reset. A circuit breaker is different.
  - bri3d 2y ago
    There are two kinds of thing that are both called eFuse: current-limiting devices which are almost always resettable, and one-time programmed bits which are intentionally one-time programmable (some are implemented as physical fuses which are blown by overcurrent, others are implemented using various other types of write-once nonvolatile memory, and some bad ones are implemented by making normal flash pretend to be write-once using firmware-level protections). Professionally I usually see OTP referred to as "fuses," "OTP," "straps," or "chicken bits," with the specific word "eFuse" reserved for the current-limiting device. But in popular media the trend seems the opposite.
  - ChrisClark 2y ago
    Why would that be the assumption? An eFuse is a literal trace that gets burnt up, you can't connect it back again.
xvfLJfx9 2y ago
You can't lol. How do you wanna restore a blown fuse on nanometer level INSIDE the GPU die. Its simply not possible. By the way, AMD also uses fuse blowing if you e.g. overclock some of their CPUs to mark them as warranty voided. They give you a warning in the BIOS and if you resume a fuse inside the CPU gets blown that will permanently indicate that the CPU has been used for overclocking (and thus remove the warranty)
- guerrilla 2y ago
  > How do you wanna restore a blown fuse on nanometer level INSIDE the GPU die. Its simply not possible. Bullshit. There will be hackers in the future who can do it in their garage. Just... not anytime soon. > By the way, AMD also uses fuse blowing if you e.g. overclock some of their CPUs to mark them as warranty voided. They give you a warning in the BIOS and if you resume a fuse inside the CPU gets blown that will permanently indicate that the CPU has been used for overclocking (and thus remove the warranty) Emphasis on "some." You can buy plenty of CPUs from them made for overclocking.
  - Kirby64 2y ago
    > Bullshit. There will be hackers in the future who can do it in their garage. Just... not anytime soon. I'll take your bet on this. Silicon designers aren't unaware of this potential vulnerability, and if you want to prevent eFuses from being un-blown, you can design for that. I would place money on there not being any commercially viable way to restore an eFuse in a 4090 die at any point in the future. You can probably do it, but it would require millions of dollars in FIB and SEM equipment and likely would destroy the chip for any useful purpose. Usually the only useful reason to attempt to recover/read/unblown fuses is to read out private keys built into chips.
    - guerrilla 2y ago
      > You can probably do it, but it would require millions of dollars in FIB and SEM equipment and likely would destroy the chip for any useful purpose. The price tag and size of these things are what I'm talking about. SOME day it will get much cheaper and smaller. A 4090 will be useless at that point, but I still play with 8086s and vacuum tubes, so... No point in betting though. We'll both be dead by then.

e-fuses (https://en.wikipedia.org/wiki/EFuse https://en.wikipedia.org/wiki/EFuse) are typically etched into the silicon as an exactly-once operation, meant to irrevocably set a configuration. Some devices, for instance, have an e-fuse that makes it impossible to change cryptographic trust signatures after the e-fuse has been blown.

sabareesh 2y ago
That's intriguing; one might assume that a key feature of eFuse would be the ability to reset easily. But I guess it could be implemented without it
- wmf 2y ago
  No, the essence of a fuse is that it can never be reset. A circuit breaker is different.
- bri3d 2y ago
  There are two kinds of thing that are both called eFuse: current-limiting devices which are almost always resettable, and one-time programmed bits which are intentionally one-time programmable (some are implemented as physical fuses which are blown by overcurrent, others are implemented using various other types of write-once nonvolatile memory, and some bad ones are implemented by making normal flash pretend to be write-once using firmware-level protections). Professionally I usually see OTP referred to as "fuses," "OTP," "straps," or "chicken bits," with the specific word "eFuse" reserved for the current-limiting device. But in popular media the trend seems the opposite.
- ChrisClark 2y ago
  Why would that be the assumption? An eFuse is a literal trace that gets burnt up, you can't connect it back again.

xvfLJfx9 2y ago

You can't lol. How do you wanna restore a blown fuse on nanometer level INSIDE the GPU die. Its simply not possible. By the way, AMD also uses fuse blowing if you e.g. overclock some of their CPUs to mark them as warranty voided. They give you a warning in the BIOS and if you resume a fuse inside the CPU gets blown that will permanently indicate that the CPU has been used for overclocking (and thus remove the warranty)

guerrilla 2y ago
> How do you wanna restore a blown fuse on nanometer level INSIDE the GPU die. Its simply not possible. Bullshit. There will be hackers in the future who can do it in their garage. Just... not anytime soon. > By the way, AMD also uses fuse blowing if you e.g. overclock some of their CPUs to mark them as warranty voided. They give you a warning in the BIOS and if you resume a fuse inside the CPU gets blown that will permanently indicate that the CPU has been used for overclocking (and thus remove the warranty) Emphasis on "some." You can buy plenty of CPUs from them made for overclocking.
- Kirby64 2y ago
  > Bullshit. There will be hackers in the future who can do it in their garage. Just... not anytime soon. I'll take your bet on this. Silicon designers aren't unaware of this potential vulnerability, and if you want to prevent eFuses from being un-blown, you can design for that. I would place money on there not being any commercially viable way to restore an eFuse in a 4090 die at any point in the future. You can probably do it, but it would require millions of dollars in FIB and SEM equipment and likely would destroy the chip for any useful purpose. Usually the only useful reason to attempt to recover/read/unblown fuses is to read out private keys built into chips.
  - guerrilla 2y ago
    > You can probably do it, but it would require millions of dollars in FIB and SEM equipment and likely would destroy the chip for any useful purpose. The price tag and size of these things are what I'm talking about. SOME day it will get much cheaper and smaller. A 4090 will be useless at that point, but I still play with 8086s and vacuum tubes, so... No point in betting though. We'll both be dead by then.