23 Nov
2015
23 Nov
'15
4:54 p.m.
From: Paul Koning
Sent: Monday, November 23, 2015 11:26 AM
> On Nov 23, 2015, at 1:00 PM, Johnny Billquist
<bqt at Update.UU.SE>> wrote:
> As far as I can tell, disks fall into two groups,
as far as massbus control
> is concerned. The RM02, RM03, RM05, RM80 and RP07 is one group. The RP04,
> RP05, RP06 is another. A few register addresses between the groups are the
> same, but the actual register at that address is different. But if I
> remember right, it's registers that have to do with error recovery, so
> potentially not something people would care about in emulation anyway. But
> it still means there are different drivers in the OS for them.
[snip]
> And of course, you also have the TM02/TM03 and
TM78, which have yet again
> different registers on the massbus.
Yes. And mixing disk and tape on a massbus is
something that I don't think
was done on PDP-11s. It certainly could have been done, and it was on VMS
and/or TOPS if I remember right.
Two things.
1) There is not such things as "TOPS". The 2 operating systems for the PDP-10
provided by DEC are Tops-10 and TOPS-20. The only thing they have in common
is the first 4 letters (modulo case) of the names. They share exactly no
code in the monitor ("kernel"), and do not even have the same origins.
Tops-10 started as the monitor on the PDP-6, in 1964, and was in continuous
development until 1988 (and in maintenance until 1993+), while TOPS-20 began
life as the TENEX operating system from BBN c. 1969, licensed for the new
KL-10 processor while that was under development. TOPS-20 v1 appeared in 1975.
BBN developed a run time package for TENEX called PA1050 which handled a
subset of the Tops-10 system calls by merging into user-mode programs and
intercepting them; DEC carried on the same mechanism to allow Tops-10 compilers
and other utilities to run on the new OS while native versions were developed.
2) Having stated all that, Tops-10 does not allow mixing tapes and disks on a
channel, but it does allow mixing disk drive types. TOPS-20 has always
allowed mixing tapes and disks on a channel.
Rich
Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134
mailto:RichA at LivingComputerMuseum.org
http://www.LivingComputerMuseum.org/