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> especially audio stuff. https://news.ycombinator.com/item?id=35919612 https://news.ycombinator.com/item?id=35919612 tldr: https://devblogs.microsoft.com/old
by rasz 3y ago
> especially audio stuff.
https://news.ycombinator.com/item?id=35919612 https://news.ycombinator.com/item?id=35919612
tldr: https://devblogs.microsoft.com/oldnewthing/20160411-00/?p=93281 https://devblogs.microsoft.com/oldnewthing/20160411-00/?p=93... Intel screwed up implementing v86 mode by missing one privileged accesses trap - Protected Mode program (CPL 3) executing CLI and expecting POPF to restore interrupt flag. CLI will correctly trap, but POPF is silently ignored AND doesnt trap. No easy workarounds available.
- rep_lodsb 3y agoThat's in protected mode. In V86 with IOPL < 3, both PUSHF and POPF will trap. However I think some versions of Windows used to run V86 code with IOPL = 3. At least I remember being able to run "CLI, HLT" instructions in DEBUG inside a DOS box and locking up the entire system.
- rasz 3y agoYes, you are right, sorry. Should be "Intel screwed up implementing Protected Mode by missing one privileged accesses trap - Protected Mode program (CPL 3, IOPL < 3) executing CLI and expecting POPF to restore interrupt flag. CLI will correctly trap, but POPF is silently ignored AND doesnt trap. No easy workarounds available." One of the prominent victims is Doom. Works in Windows only due to hacks.