Writing a BIOS bootloader for 64-bit mode from scratch

Re:Writing a BIOS bootloader for 64-bit mode from scratch by rwmj on Sunday July 14, 2024 @09:46AM (#40960952)

What's the reason why FreeDOS can't use the CSM (the BIOS compatibility mode of UEFI)?

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Re:Writing a BIOS bootloader for 64-bit mode from scratch by EvanAnderson on Sunday July 14, 2024 @09:51AM (#40960986)

AFAIK it can. I believe some UEFI implementations don't have CSM.

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Re:Writing a BIOS bootloader for 64-bit mode from scratch by p_l on Monday July 15, 2024 @08:05AM (#40967079)

a Type 3 UEFI implementation has no CSM, Type 2 has CSM available, Type 1 enforces booting into CSM (what many "BIOS"es actually was in later days)

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Re:Writing a BIOS bootloader for 64-bit mode from scratch by EvanAnderson on Monday July 15, 2024 @11:41AM (#40968861)

Thanks for that. That sent me down an enjoyable rabbit hole. I got started with PCs back in the 80s and became fairly familiar with how boot worked back then. UEFI happened while I was paying attention to other things and I've never become as familiar with it as I should be. This was a good excuse to do some reading.

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Re:Writing a BIOS bootloader for 64-bit mode from scratch by deaddodo on Monday July 15, 2024 @11:42AM (#40968873)

Just for clarification's sake, the proper terminology is "UEFI class" not "type".

Otherwise, this is accurate.

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