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

Michael Schierl schierlm at gmx.de
Fri Jul 23 23:47:06 CEST 2021

Am 23.07.2021 um 13:15 schrieb Liam Proven:
> On Fri, 23 Jul 2021 at 00:08, Michael Schierl <schierlm at gmx.de> wrote:
>> You wanted to say, an OS with no direct Hard Disk support on its own.
>> (It is the same if you boot from an IDE/SCSI/SATA hard drive).
> No, I really did not. Please do not try to put words into my mouth :-(

Sorry for that.

> DOS has hard disk support, and has since version 2.0 in 1983.

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. CDROM
with mscdex was a complete different beast, though.

> Secondarily, SCSI went through parallel evolution of its own but most
> PC SCSI host adaptors included an auxiliary ROM BIOS that extended
> support for SCSI drives to DOS.

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

> (I would say "and to other PC OSes that used the BIOS" but I can't
> think of any. Most of them just ran on top of DOS. Maybe DR CP/M086,
> Concurrent CP/M, Concurrent DOS and DOS Plus?)

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 and if I
recall corretly I had one machine with some quirky IDE controller where
it was needed. It was possible to enable by pressing the spacebar at the
right moment while booting the install media. (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".

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.

> This is true. However, the start-off-a-USB-disk method needs no
> modification to the DOS OS or config files. You can copy an installed
> copy of DOS (with no USB drivers or support) onto a USB key, boot off
> the USB key, and suddenly DOS can see and use the USB drive.

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:.

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

>> What is your experience with support of contemporary mice/touchpads in
>> DOS? Oberon without mouse would not be much fun.
> So far, I am mostly using various laptops, and everything just seems
> to work.

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.



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