PDOS on ARM

[Paul Edwards]

There is an operating system that basically looks the
same as MSDOS called PDOS, which already successfully
runs on the 80386.

I have ported a different (ie more portable) flavor to ARM
as proof of concept, and it does work, including on a
smartphone and tablet, but there are some issues, the
biggest of which is that it apparently doesn't work on a
64-bit processor, even one that supports 32-bit mode.

The second-biggest issue is that it randomly crashes.

Is anyone interested in working on this?

https://github.com/jeanmarclienher/Pdos-PdAndro

http://pdos.org

Thanks. Paul.

[Paul Edwards]

On 08/12/22 13:21, Paul Edwards wrote:

> There is an operating system that basically looks the
> same as MSDOS called PDOS, which already successfully
> runs on the 80386.
>
> I have ported a different (ie more portable) flavor to ARM
> as proof of concept, and it does work, including on a
> smartphone and tablet, but there are some issues, the
> biggest of which is that it apparently doesn't work on a
> 64-bit processor, even one that supports 32-bit mode.

I can't remember which processor this was,
but I started afresh with a Pinebook Pro
laptop, and gccarm was crashing because it
did floating point. qemu-arm doesn't have
this problem, and so I was able to use that,
and I also switched to using SubC as the
compiler which doesn't use floating point,
so I can compile with that instead.

Fortunately binutils didn't use floating
point.

Note that I was not successful attempting
to get gccarm to use floating point emulation
instead.

There are other options (qemu-system-aarch64
in 32-bit mode with enable-kvm and UEFI may
be an alternative, or maybe I can find an
appropriate floating point emulator for the
64-bit machine that handles 32 bit, or maybe
I can upgrade the software suite to 64-bit)
that may solve the problem.

> The second-biggest issue is that it randomly crashes.

There seems to be some timing issue with
putting code into BSS and then executing it.
Adding a delay of 0.02 seconds was enough
to stop the crashes.

> http://pdos.org

New version under UCARM.

BFN. Paul.