UNIVS: Unix for J-11 or 11/84

[jack at boring.UUCP]

In article <6552 at utzoo.UUCP> henry at utzoo.UUCP writes:
> [Replying to an article asking how to configure V7 for a J-11]
>
>Long odds you will find that the thing acts pretty much like a 70 as far
>as Unix is concerned.  To V7 Unix, with the exception of one or two fine
>details of which registers are printed in the event of a memory-system
>error, a 44 looks *exactly* like a 70 with Unibus disks.  The "Unibus
>disks" part requires a couple of small changes to the bootstrapping code,
>which ignores the Unibus map since Bell Labs's 70s had Massbus disks and
>45s didn't have the map.

Quite right, but the gotcha is in the 'couple of small changes'.
It took me *weeks* to find out why the machine didn't boot.....
Anyway, for those of you facing the problem (I tried sending the
original poster some info, but it bounced): The problem is that
the unibus map is turned on very soon in initialization. This means
that non-massbus devices won't be able to load the kernel, since
the mapping is incorrect. Wait with turning the map on until your
kernel is more-or-less running. I think I did it somewhere in main(),
after counting memory.

Something else: If my memory serves me right, a J-11 doesn't have
separate I/D. This would make it look more like an 11/34 with with
a 22 bit bus, or an 11/24+ (I think).
If you have a standard V7, this might give you some problems. I seem
to remember that there's some unibus map code that is only enabled when
you run on a separate I/D machine.
-- 
	Jack Jansen, jack at mcvax.UUCP
	The shell is my oyster.