[Oberon] Re (2): Copy or reinstall A2?

Liam Proven lproven at gmail.com
Tue Jul 27 15:53:00 CEST 2021

On Fri, 23 Jul 2021 at 23:47, Michael Schierl <schierlm at gmx.de> wrote:
> Sorry for that.

It's OK.

> I wanted to say, no direct support for hard disk controller drivers. If
> Int 13h is able to access the hard disk, DOS will use it. If I recall
> correctly, hard disk "drivers" for DOS actually hooked Int 13h.

I think that's right but I was never a DOS API-level programmer.

But DOS barely has device drivers for anything. It doesn't even have
CD drivers -- they must be provided by someone else. All it provides
(in later versions) is the redirector. DOS was barely an OS at all,

All I was getting at is that while it _does_ directly support hard
disk drives, it doesn't support USB -- but if you boot it from a USB,
the BIOS fakes support for the USB drive in a way that DOS can use.
This does not seem to be widely-known, and it's useful. DOS booted
from USB is entirely useful, quite fast, and as it doesn't write much
to the drive anyway, a DOS-bootable USB stick should last a long time.

Finally, as 32MB was a fair amount of space for DOS and DOS apps, even
very small USB drives are entirely usable for this. 2GB or 4GB USB
drives are _huge_ by DOS standards.

> with mscdex was a complete different beast, though.


> Today, controllers contain both an option ROM for DOS and another one
> for (U)EFI.

I did not know that, but on consideration, it makes sense.

Over on the FreeDOS list, there is much debate as to whether FreeDOS
can or even should be made UEFI-compatible.

> In the "Hobby OS" space, there are a few that use Int 13H in real mode
> to communicate with hard disks. I also believe BeOS (5) had a setting
> that used Int 13H in 16-bit real mode for all disk access

(!) I didn't know that, and I did use BeOS 5 a bit. I gave it a rave
review in the UK's leading computer magazine, Personal Computer World
(PCW -- *not* the same journal as the American PC World.)

>  (Of course, Windows 95
> also had a DOS compatibility mode which handled all disk access via DOS,
> but I think that counts as more-or-less "runs on top of DOS".

Yes, and yes. It was necessary to run Win95 on Acorn's 386 & 486
add-in processor boards for the ARM-based RiscPC.

> Also some boot loaders (like e.g. GRUB) are getting to some complexity
> that is almost its own OS. And when using GRUB with the biosdisk module
> (which is default, unless you are on (U)EFI where it uses efidisk) it
> will use BIOS to access the disk and load the kernel etc.

I did not know that. This thread is proving very informative.

> Which is no different from having a DOS floppy image in Floppy Emulation
> Mode on an El Torito CDROM. DOS will see and use the floppy drive (as
> A:) and any physical drive A: will then become drive B:.

I would argue it is different in quite a few ways.

The floppy-emulation approach also can be made to work with USB keys, I think.

The key differences are:
• even if the medium is writable, the virtual floppy isn't;
• space is very constrained;
• as an emulation, it isn't extensible -- e.g., you can't have more partitions.

Whereas a bootable USB just looks like any other HDD to DOS. You can
cache it, write to it, partition it, format it, install apps onto it,
etc. All without any drivers.

As far as I can tell from my testing, this is also compatible with
32-bit DOS-extender programs. So, for instance, it should be
compatible with DOS Oberon.

> MEMDISK (from the syslinux project) can also load floppy or hard disk
> images into RAM and DOS will just see them fine.

I have not seen or tried this.

> So I guess it is better than mouse support in (U)EFI. The laptop I'm
> sitting at right now supports external USB mice but not the internal
> trackpad. If the mouse has been connected before powering up the machine.


I am not surprised, though. UEFI feels very unfinished to me and I
find it a nuisance to use.

Liam Proven – Profile: https://about.me/liamproven
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