[SOLVED] Destroying CPU with microcode update

[Rukog]

While browsing the System Programming Guide, Part 1

I am reading this

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

[Octocontrabass]

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.

[iansjack]

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.

[nullplan]

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.

[iansjack]

As far as I am aware the voltages to the CPU are not controlled by the microcode.

[Octocontrabass]

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.

[iansjack]

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.