On 2015-09-24 01:15, Antonio Carlini wrote:
On 21/09/15 14:15, Noel Chiappa wrote:
> From: tony duell
> In some cases it should be possible to write a machine code
program
> that executes on 2 processors with wildly different instruciton
sets.
I have this bit set that I was told (or something, the memory is _very_
vague) that early versions of the KL-10 had this hack; the root block
on the
disk was the boot block both the PDP-10 and the PDP-11 front end
machine, and
the first instruction or two was very cleverly construced and sent the
two
machines different ways. Alas, I looked in the front-end PDP-11 code
(in the
KLDCP; directory) and saw no signs of this, so maybe it was an urban
legend?
I can't find a definitive reference right now, but I *think* that the
ODS-1 disk format
was first used on the PDP-11 and then later used in early versions of
VMS. I *think*
that it was arranged such that a PDP-11 booting and a VMS system booting
could
be done from the same disk by arranging for each to interpret the boot
block in
a way that each was happy with.
I think that is incorrect, since early VMS didn't havea boot block. The
VAX-11/780 was always booted from the PDP-11, and it started with VMB.
VMB was gotten from the FE, and VMB in turn understood the file system.
It wasn't until the VAX-11/750 that DEC did a VAX that used boot blocks.
And then, of course, the boot block is just the first block(s) on the
disk. Don't matter what file system you might have...
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
