> On Fri, 28 Jul 2000, John Honniball wrote:
>
> > Oh, and if you try to boot a non-bootable disk, you get a
> > nice friendly message about that disk being a data disk --
> > now why couldn't they make it say something when there's NO
> > disk??
I've seen boot blocks that contain enough code to print out a message that
you've tried to boot a data disc. Trying to boot an unformatted disk in
such a machine will likely result in the endless seek. Eventually,
manufacturers moved that functionality into the ROM/BIOS code, but in the
PDP-11 days, you could boot a system by writing bits manually into
device registers to initiate a transfer of the first part of the disk
into low core. I used to know the exact ODT sequence to boot an RL-11
in an 11/24 because I didn't own RL02 boot ROMs. It was about three or
four commands. It worked because it takes a human a finite amount of
time to enter in all the commands and that gives the drive time to read
the block between, like, the third and fourth steps, removing the need
to write a boot block that initiates a transfer and loops until the
controller shows that the operation is complete.
It all comes down to how smart you want the machine to be at boot time
versus how flexible you want the booting scheme.
-ethan
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Received on Fri Jul 28 2000 - 16:56:10 BST