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You know you're doing low level stuff when the guide mentions things like > Also consider using older CPU microcode without the microcode mitigations for CPU v
by WJW 6y ago
You know you're doing low level stuff when the guide mentions things like
> Also consider using older CPU microcode without the microcode mitigations for CPU vulnerabilities.
I don't think I even know where to find older microcode for my particular CPU.
- wtallis 6y agoUsing older microcode is just a matter of preventing your OS from uploading newer microcode during the boot process, and not updating the motherboard firmware to a newer version that bundles newer CPU microcode. Rolling back the motherboard firmware is usually not a supported option, and sometimes is actively prohibited by the system.
- WJW 6y agoSo how would I acquire a processor without the mitigations at this point? Presumably all the new ones are sold with them already installed.
- wtallis 6y agoCPUs do not have non-volatile memory for storing microcode updates. It has to be uploaded from the motherboard during the boot process, and the OS can optionally upload a newer version as part of their boot process. So the difficult thing is finding a matching motherboard that's running an old enough firmware version, or that can be rolled back to an older firmware version.
- formerly_proven 6y agoSocketed BIOS chips used to be somewhat common in gaming boards, which would always allow you to downgrade the firmware. I don't think they're found in workstation or server boards.
- segfaultbuserr 6y agoIf the BIOS EEPROM chip is not a socketed DIP-8 package, often it uses a surface-mount SOIC-8 chip, which can be easily programmed with a SOIC-8 test clip and an I2C/SPI programmer. In case you don't have one, you can also use any single-board computer, like a Raspberry Pi and flashrom for the job.