On Tue, 4 Dec 2018, Liam Proven wrote: > > I don't know if the unreal mode has been retained in the x86 architecture > > to this day; as I noted above it was not officially supported. But then > > some originally undocumented x86 features, such as the second byte of AAD > > and AAM instructions actually being an immediate argument that could have > > a value different from 10, have become standardised at one point. > > I know, and was surprised that, v86 mode isn't supported in x86-64.
In the native long mode, that is. If you run the CPU 32-bit, then VM86 works. I guess AMD didn't want to burden the architecture in case pure 64-bit parts were made in the future. > This caused major problems for the developers of DOSEMU. And also for expansion-BIOS emulation, especially with graphics adapters (which, accompanied by scarce to inexistent hardware documentation, made mode switching even trickier in Linux than it already was). It looks like fully-software machine code interpretation like with QEMU is the only way remaining for x86-64. Maciej