[pups] (no subject)

Johnny Billquist bqt at update.uu.se
Wed Feb 26 23:04:39 AEST 2003

On Wed, 26 Feb 2003, Christos Papachristou wrote:

> A few questions from a newbie:
> I have installed 2.9BSD on a microPDP11/73 with an RD52, using the MSCP
> version of Jonathan Engdahl. After startup the kernel
> indicates 160kb of memory .I am not familiar with such an old unix to
> find out the details but  I understand it as 256k minus the kernel. The memory
> is M8067-LF i.e. 512k Qbus. Does this mean that the system can't see the
> rest of it and that I have configure/recompile the kernel?
> The system seems anyway to run fine.

Are you sure it's reporting bytes, and not words?

> I haven't seen an operational PDP with UNIX before this,
> so I can't judge its speed. When in single user mode it seems to
> me that it runs "fast". However upon entering multi user mode the speed
> drops dramaticaly. I have not yet compiled in the 8 port multiplexer
> (DHV11-A), so only the console is functional and thus no gettys are
> loaded. So ,why is there such a change in speed? Does the multiuser mode
> just rise the nice value of the console tasks?

There shouldn't be a big difference in speed. Are you starting some heavy

> Some information on the system. It is a KDJ11-B (M8190 -no suffix) i.e. an
> 11/84. So, the label on the system says microPDP11/73 (in an BA23 enclosure)
> the cpu is an 11/84 (if the FPU socket is the DIP-40 slot then it is
> unused), and the  2.11BSD second stage boot (version from vtserver) I
> have tried indicates 11/83. The memory is after the CPU and is Qbus (M867-LF).
> If I have understood what I have read in the list, this must be a mixed
> system that could use PMI memory, but just uses Qbus?? What exactly is my
> system?

There exists a specific 11/73 CPU card, but we'll ignore that for now.
The 11/73, 11/83 and 11/84 all use the same CPU card.
The differences are in other areas, and cannot always easily be detected
by software.
The difference between an 11/73 and 11/83 is if the system have Qbus
memory or PMI memory. The difference between an 11/83 and 11/84 is if the
system have the KT84 (or whatever the card is called, my memory fails me
at the moment) Unibus map, which is a Q-bus to Unibus converter along with
the Unibus map required. The CPU is always on a Qbus, but in the 11/84,
nothing but CPU and PMI memory is on this bus.

> Moreover the MSCP controller (M8639 YP i.e. RQDX1)
> the serial port multiplexer(M3104 i.e. DHV11-A) and the memory are Qbus while
> the cpu board is indicated as Unibus in the field guide. Can these two bus type
> s be mixed? (If yes , i would be tempted to abuse the dead VAX11/780 in the
> basement. Can this be done?).

As stated above, the CPU card is actually always Qbus. In the 11/84 you
have a bus adapter to connect the Unibus.

> Anyway, I thought that the best choice of
> a UNIX for it since it only has an RD52 woulbe 2.9 BSD with MSCP support.
> Was this a good guess?

Yes, since you probably don't want to pay a lot of money to Mentec for one
of their OSes. 2.11 is much nicer, but you'll want more memory and disk
space for that.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt at update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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