3 ms·
Is PC-AT style "get the keyboard controller to reset the CPU, then have special BIOS code detect situation and jump to your code?" still available in modern sys
by fredoralive 7y ago
Is PC-AT style "get the keyboard controller to reset the CPU, then have special BIOS code detect situation and jump to your code?" still available in modern systems? Real mode is sortof a supervisor mode.
Of course you would have to make the KBC low level accessible to user mode which may cause issue processing legacy input devices. Plus having to reinitialise protected mode every system call might cause some efficiency issues.
- dfox 7y agoIIRC enough of the KBC is still present that this might actually work, another question is whether modern UEFI firmware actually handles the SW-induced reboot. As for entering and exiting protected mode: that is in fact surprisingly fast operation assuming that all the relevant data structures are still in place. In fact DOS XMS managers (and VxD-based Windows) switch between PM with vm86, true real mode and various unreal-ish (ie. real mode with weird values in descriptor shadow registers) modes quite regularly.