How to update BIOS on computer that won't boot up?
If you are using an AMD platform, fill out a warranty request for 'boot kit required'. They will send you a cheap APU that can be used to update your bios. https://www.amd.com/en/support/kb/faq/pa-100#faq-Short-Term-Processor-Loan-Boot-Kit
If you are using an Intel platform, some Intel motherboards have a way to update bios without the CPU. Check your manual. On Gigabyte boards, the feature is called "Qflash Plus". On Asus boards, the feature is "USB BIOS Flashback".
If this doesn't work out for you, you can order a compatible processor and return it after doing the update. Some retailers have a formal process for doing this so you don't have to renege them.
In addition to Andy's excellent info, MSI motherboards also have a BIOS Flashback button on the rear panel (so you don't have to open up the case) that enables updating the BIOS with an FAT32 formatted USB drive. I have a MEG Z390 ACE motherboard. The instructions are:
- Connect power supply to CPU_PWR1, CPU_PWR2 and ATX_PWR1. (No other components are necessary but power supply.)
- Plug the USB flash drive that contains the MSI.ROM file into the BIOS FLASHBACK+ port on rear I/O panel.
- Press the BIOS FLASHBACK+ button to flash BIOS, and the light of BIOS FLASHBACK+ button starts flashing.
- After the flashing BIOS process is 100% completed, the button light would stop flashing and would be off simultaneously.
These instructions were copied and pasted from the PDF of the user's manual.
I imagine the instructions are pretty close to identical for other newer MSI boards, as well.
Assembling a PC from parts is fun and educational, but sometimes also slow and frustrating, when you get stuck on things like this. One solution is to buy, or borrow, the cheapest compatible cpu you can find, and temporarily replace your real cpu, to do the update.