dosemu on x86_64

dosemu on x86_64

[jegunn]

I saw the post lamenting the fact that the virtual machine support
which dosemu uses is absent from the x86_64 kernels hours before
I tried to install and run dosemu on a shiny new Athlon 64 machine
I just finished. It does not work, of course, as advertised. Is there
any ruse one can use to make it work, however inconvenient?

thanks in advance,

jim gunn

Re: dosemu on x86_64

[Stas Sergeev]

Hello.

jegunn wrote:
> I tried to install and run dosemu on a shiny new Athlon 64 machine
> I just finished. It does not work, of course, as advertised. Is there
> any ruse one can use to make it work, however inconvenient?
You can either just run the i386
linux kernel rather than the
x86_64 one on your Athlon64, and
then the dosemu will work.
Or you can use some very old
versions of the qemu emulator in
user mode, to run dosemu (with the
limited functionality) even on the
x86_64 kernel. Or you can try the
dosbox instead (another DOS emulator).

Note: I am not the Athlon64 owner,
they should know better how well
does dosemu work in that circumstances.

Re: dosemu on x86_64

[Paul Lyon]

Does anyone know why the kernel coders cut out support for the virtual
8086 mode in 64 bit mode? Did AMD just not include the microcode or
hardware support for shifting to virtual 8086 mode from 64 bit mode? I
suppose there might be complexities in memory addressing to work around,
but if one can make the shift running in 32 bit mode...

If they don't manage to restore this feature, that may keep me from buying
an Opteron motherboard for rather a while.

Ciao,

Paul Lyon

Re: dosemu on x86_64

[Stas Sergeev]

Hello.

Paul Lyon wrote:
> Did AMD just not include the microcode or
> hardware support for shifting to virtual 8086 mode from 64 bit mode?
AMD answers your question here:
http://www.x86-64.org/lists/discuss/msg03333.html

> If they don't manage to restore this feature, that may keep me from 
> buying an Opteron motherboard for rather a while.
One can't always depend on the
legacy things. v86 can't live
forever.

Re: dosemu on x86_64

[Paul Lyon]

On Tue, 24 May 2005, Stas Sergeev wrote:

> Hello.
>
> Paul Lyon wrote:
> > Did AMD just not include the microcode or
> > hardware support for shifting to virtual 8086 mode from 64 bit mode?

> AMD answers your question here:

> http://www.x86-64.org/lists/discuss/msg03333.html

Thanks for the reference. So the hardware is there, but apparently it is
complicated enough, and slow enough, that the kernel coders decided not to
bother with it. I wonder if the CPU designers could have made
it simpler and faster if they had added some more transitors. Perhaps
they decided that it wasn't worth the bother either.

> > If they don't manage to restore this feature, that may keep me from
> > buying an Opteron motherboard for rather a while.

> One can't always depend on the
> legacy things. v86 can't live
> forever.

Forever is a long time :-) For the present, there is rather a lot of DOS
software outthere that is unlikely to be ported to, or adapted/upgraded
to, more recent OS's, and if it is, it will be Win XP or some successor,
not Linux. A lot of that is games, of course, but I would wager that most
of the audience has some DOS games they would be reluctant to be unable to
play anymore without booting back into plain old DOS. In my case, besides
the games, there are two very useful programs, at least, that I use for
writing and software development/documentation, at least one of which is
still an unported dos program, and the other of which is, it seems, at
present an unfinished Win32 port (no Linux users need apply :-( These are
commercial packages from a small software house, but there is nothing
comparable in the free software world.

Ciao,

Paul Lyon
http://www.la.utexas.edu/~plyon