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| [SOLVED] Destroying CPU with microcode update https://forum.osdev.org/viewtopic.php?f=13&t=49846 |
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| Author: | Rukog [ Thu Aug 05, 2021 8:04 am ] |
| Post subject: | [SOLVED] Destroying CPU with microcode update |
While browsing the System Programming Guide, Part 1 I am reading this Attachment: q.png [ 64.29 KiB | Viewed 9483 times ] Is any of you already success to change behavior of some instructions, thus OS crash all the time and the BIOS too. It's for the science team 
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| Author: | Octocontrabass [ Thu Aug 05, 2021 3:17 pm ] |
| Post subject: | Re: Destroying CPU with microcode update |
It's been done. Of course, that only works if you have a way to load unsigned microcode. AMD added a signature check to their later CPUs, and Intel CPUs have always checked the signature. There's a hardware exploit that allows bypassing the signature check on some Intel CPUs. |
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| Author: | iansjack [ Tue Aug 10, 2021 8:28 am ] |
| Post subject: | Re: [SOLVED] Destroying CPU with microcode update |
The. title of this thread is rather misleading. A microcode update is not permanent, and is lost on reboot. It can hardly destroy a CPU. |
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| Author: | nullplan [ Wed Aug 11, 2021 11:16 am ] |
| Post subject: | Re: [SOLVED] Destroying CPU with microcode update |
Well, couldn't a microcode update cause a hardware malfunction so catastrophic that the wrong voltages get sent to the CPU, thus destroying it? OK, I admit, that is reaching. |
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| Author: | iansjack [ Wed Aug 11, 2021 1:43 pm ] |
| Post subject: | Re: [SOLVED] Destroying CPU with microcode update |
As far as I am aware the voltages to the CPU are not controlled by the microcode. |
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| Author: | Octocontrabass [ Wed Aug 11, 2021 2:58 pm ] |
| Post subject: | Re: [SOLVED] Destroying CPU with microcode update |
They might be controlled by the firmware's SMM code, which is affected by microcode. I'd be more concerned about microcode blowing one of the OTP fuses inside the CPU. |
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| Author: | iansjack [ Wed Aug 11, 2021 11:32 pm ] |
| Post subject: | Re: [SOLVED] Destroying CPU with microcode update |
When someone can provide a proof of concept of custom microcode trashing a CPU then I'll believe it's a possibility. If that's what you want to do I would have thought a BIOS modification was a simpler means. |
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