20 Jul
2010
20 Jul
'10
11:20 a.m.
Hello,
I recently acquired my first DEC PDP. It is a VT103 (VT100 terminal with
a PDP 11/23 inside). It came with a pair of cartridge disk drives (HEAVY!)
that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives), boxes
of manuals, 3 DEC operating systems, software, and an extra VT100.
While the DEC operating systems are OK, I am actually interested in using
the machine to (finally) go through "Lions' Commentary on Unix" (Unix V6),
using software downloaded from http://www.tuhs.org/. (Lions' book here):
http://www.amazon.com/dp/1573980137/
After I do that, I want to move up to Unix v7, 2.9BSD, and try other Unix
distros available for the PDP.
My concern is that the 18-bit PDP 11/23 does not have enough memory.
It currently has 128KB installed, with a maximum of 256K possible after a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I
can get with just 128KB memory? Can I get through Lions' book?
I am looking at adding wires to the backplane to make it a 22-bit machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and
4MB sizes). However, I am not ready to dive in and start modifying the qbus
backplane for 22-bit addressing just yet. So my question is:
Rather than invest in a 256KB memory board designed for the 18-bit qbus,
can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit system,
and just use the first 256KB for now? Also, is the VT103 backplane
compatible with a quad-height memory board? (It only has dual-height
cards installed at the present time).
Parts inventory:
- VT103, with:
- 4x4 qbus backplane, 18-bit. The manual says "two H803s (2x4 connector
blocks, stacked vertically in a 4x4 configuration)". I know there are
possible issues with "straight" vs. "serpentine" slots, but I have
not
got that figured out yet on the VT103.
- M8186 KDF11-A CPU (Newer revisions of KDF11-A's are 22-bit capable).
http://world.std.com/~mbg/pdp11-field-guide.txt
says: "(Prior to etch rev. C, 18-bit addressing only. ...)"
I could not find revision information on the M8186 board, but "146 CA"
is stamped into one of the red plastic handles. I can email close-up
photos to anyone who wants to take a look and determine if this is a
rev C or later board capable of 22-bit addressing.
- M8043 Quad Serial board. This doc says it is 22-bit compatible:
http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardwar…
- M8029 (RXV21) floppy disk board (18-bit DMA only). -Will this be a
problem with Unix v6 or 2.9BSD if running with 22-bit addressing?
- M8208 "VT103 Maintenance Module" (Unknown if 22-bit compatible).
- Xylogics C510 (formerly called "Wizard 1") cartridge disk controller
board, with 18-bit addressing, connected to a pair CDC 9427H "Hawk"
disk drives (one disk drive is DOA, but the other is OK).
- 3rd party memory board (128KB), Christlin Industries, Inc.
So, initially I want to run a 22-bit memory board (M7551) in an 18-bit
VT103 qbus backplane, and access only the first 256KB of memory using
18-bit addressing. Is this possible? Thank you for your help.
Scott M.
20 Jul
20 Jul
11:54 a.m.
On 20/07/2010 19:20, Scott M wrote:
I recently acquired my first DEC PDP. It is a VT103
(VT100 terminal with
a PDP 11/23 inside).
It would originally have been an 11/03 card.
It came with a pair of cartridge disk drives (HEAVY!)
that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives), boxes
of manuals, 3 DEC operating systems, software, and an extra VT100.
While the DEC operating systems are OK, I am actually interested in using
the machine to (finally) go through "Lions' Commentary on Unix" (Unix V6),
using software downloaded from http://www.tuhs.org/. (Lions' book here):
http://www.amazon.com/dp/1573980137/
After I do that, I want to move up to Unix v7, 2.9BSD, and try other Unix
distros available for the PDP.
My concern is that the 18-bit PDP 11/23 does not have enough memory.
It currently has 128KB installed, with a maximum of 256K possible after a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I
can get with just 128KB memory? Can I get through Lions' book?
Probably. My 11/23 runs Seventh Edition UNIX in 256KB quite happily.
Modulo some swapping to disk, that is.
I am looking at adding wires to the backplane to make
it a 22-bit machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and
4MB sizes). However, I am not ready to dive in and start modifying the qbus
backplane for 22-bit addressing just yet. So my question is:
Rather than invest in a 256KB memory board designed for the 18-bit qbus,
can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit system,
and just use the first 256KB for now?
Yes, you can do that. Just check the power requirements, and whether
the specific card(s) are compatible with a serpentine backplane.
Also, is the VT103 backplane
compatible with a quad-height memory board? (It only
has dual-height
cards installed at the present time).
Parts inventory:
- VT103, with:
- 4x4 qbus backplane, 18-bit. The manual says "two H803s (2x4 connector
blocks, stacked vertically in a 4x4 configuration)". I know there are
possible issues with "straight" vs. "serpentine" slots, but I
have not
got that figured out yet on the VT103.
It's serpentine. Every dual slot can hold a dual card; some quad cards
are compatible and some not. There's some backplane information at
http://www.dunnington.u-net.com/public/PDP-11/QBus_chassis
though that particular version isn't listed.
- M8186 KDF11-A CPU (Newer revisions of
KDF11-A's are 22-bit capable).
http://world.std.com/~mbg/pdp11-field-guide.txt
says: "(Prior to etch rev. C, 18-bit addressing only. ...)"
I could not find revision information on the M8186 board, but "146 CA"
is stamped into one of the red plastic handles. I can email close-up
photos to anyone who wants to take a look and determine if this is a
rev C or later board capable of 22-bit addressing.
- M8043 Quad Serial board. This doc says it is 22-bit compatible:
Yes, it is.
What you need to know about I/O devices is that they don't fully decode
all the memory address bits. All I/O lives in the highest address page,
and there's a special enable signal called BBS7 that is active when (and
only when) the CPU accesses that I/O page. All sensible QBus I/O cards
decode that signal and only use the lower address bits to determine the
address within the I/O page. Quite a few memory cards use BBS7 to know
when to be DISabled, or have some other way of disabling the top 8K, so
as not to interfere with I/O.
- M8029 (RXV21) floppy disk board (18-bit DMA only).
-Will this be a
problem with Unix v6 or 2.9BSD if running with 22-bit addressing?
I'm not sure either of those actually have drivers for an RXV21. That
card will work OK in a 22-bit system without clashing with any memory
addresses, but is only useful if the driver (exists and) understands to
put the DMA buffers in the lowest 256KB. Some OS versions do exactly
that: they tell the card to transfer data to/from low memory and then
the CPU moves it if necessary (later version of RT-11 do that, for example).
- M8208 "VT103 Maintenance Module"
(Unknown if 22-bit compatible).
- Xylogics C510 (formerly called "Wizard 1") cartridge disk controller
board, with 18-bit addressing, connected to a pair CDC 9427H "Hawk"
disk drives (one disk drive is DOA, but the other is OK).
- 3rd party memory board (128KB), Christlin Industries, Inc.
Dunno about any of those, sorry.
--
Pete Peter Turnbull
Network Manager
University of York
6:06 p.m.
Pete Turnbull wrote:
I'm not sure either of those actually have drivers
for an RXV21. That
card will work OK in a 22-bit system without clashing with any memory
addresses, but is only useful if the driver (exists and) understands
to put the DMA buffers in the lowest 256KB. Some OS versions do
exactly that: they tell the card to transfer data to/from low memory
and then the CPU moves it if necessary (later version of RT-11 do
that, for example).
The DEC version of the DY.SYS device driver for an
unmapped monitor only knows about the first 64 KB
of memory, as does the RT-11 monitor. Thus only
16 bit addresses are used for the RT11FB monitor
and the DY.SYS device driver.
For the DYX.SYS device driver running under the
RT11XM monitor, the DMA on the card can handle
ONLY buffers within an 18 bit address or the first
256 KB of memory.
Thus far, you are entirely correct for the DEC versions
of the DY(X).SYS device driver.
HOWEVER, I know for certain that there is no bounce
buffer capability (which is what you have described in
your answer that the CPU moves the data if necessary)
in the DEC distribution for the DYX.SYS device driver
which runs under a mapped version of RT-11.
The reason that I know is that I enhanced DYX.SYS to
use a bounce buffer, as well as being able to handle
double sided double density 8" floppy media which
are supported on DSD 880/30 drives. The controller
on these drives is also limited to using ONLY 18 bit
addresses for the memory, hence the requirement for
a bounce buffer.
The first attempt ran well on a PDP-11/73, but slowed
to a crawl on a PDP-11/23 since the code attempted to
bounce the buffer before the I/O for the next sector was
initiated. While the code became a bit more complicated
to initiate the I/O for the next sector and then bounce the
buffer, that allowed a PDP-11/23 to keep up the normal
speed of the floppy.
Jerome Fine
11:59 a.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Scott M
Sent: Tuesday, July 20, 2010 11:20 AM
To: cctalk at classiccmp.org
Subject: DEC PDP 11/23 - OK to use 22-bit memory boards in an 18-bit
qbus?
Hello,
I recently acquired my first DEC PDP. It is a VT103 (VT100 terminal
with
a PDP 11/23 inside). It came with a pair of cartridge disk drives
(HEAVY!)
that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives),
boxes
of manuals, 3 DEC operating systems, software, and an extra VT100.
While the DEC operating systems are OK, I am actually interested in
using
the machine to (finally) go through "Lions' Commentary on Unix" (Unix
V6),
using software downloaded from http://www.tuhs.org/. (Lions' book
here):
http://www.amazon.com/dp/1573980137/
After I do that, I want to move up to Unix v7, 2.9BSD, and try other
Unix
distros available for the PDP.
My concern is that the 18-bit PDP 11/23 does not have enough memory.
It currently has 128KB installed, with a maximum of 256K possible after
a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you
estimate I
can get with just 128KB memory? Can I get through Lions' book?
I am looking at adding wires to the backplane to make it a 22-bit
machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB
and
4MB sizes). However, I am not ready to dive in and start modifying the
qbus
backplane for 22-bit addressing just yet. So my question is:
Rather than invest in a 256KB memory board designed for the 18-bit
qbus,
can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit
system,
and just use the first 256KB for now? Also, is the VT103 backplane
compatible with a quad-height memory board? (It only has dual-height
cards installed at the present time).
FYI: I've successfully run Unix 6th Ed. on a PDP-11/34 with (of course) an 18-bit
backplane, i.e. 124k words. ISTR, though, that it expects to see a front panel, and might
take issue with a Qbus machine.
I installed the software on an RK05 using Warren Toomey's VTserver software. Slow,
but effective -- Ian
12:10 p.m.
On 20/07/2010 19:20, Scott M wrote:
My concern is that the 18-bit PDP 11/23 does not have
enough memory.
It currently has 128KB installed, with a maximum of 256K possible after a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I
can get with just 128KB memory? Can I get through Lions' book?
I am looking at adding wires to the backplane to make it a 22-bit machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and
4MB sizes).
I forgot to mention one other web page:
http://www.dunnington.u-net.com/public/PDP-11/QBus_memory
lists most of the memory options in a table.
Specifically, I can tell you that an M8067 MSV11-PK, and an M7551
MSV11-Q are both OK in Q22-Q22 serpentine backplanes. For the MSV11-P
you need to ensure W1 and W2 are both in place to provide bus grant
continuity.
--
Pete Peter Turnbull
Network Manager
University of York
12:13 p.m.
On 7/20/10, Scott M <scott.m.18 at atsgate.com> wrote:
Hello,
I recently acquired my first DEC PDP. It is a VT103 (VT100 terminal with
a PDP 11/23 inside).
Nice. A bit underpowered in the PSU, but nice.
It came with a pair of cartridge disk drives (HEAVY!)
that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives), boxes
of manuals, 3 DEC operating systems, software, and an extra VT100.
Sounds like you are good to go.
While the DEC operating systems are OK, I am actually
interested in using
the machine to (finally) go through "Lions' Commentary on Unix" (Unix V6)
Ah, archaeology. ;-)
My concern is that the 18-bit PDP 11/23 does not have
enough memory.
It currently has 128KB installed, with a maximum of 256K possible after a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I
can get with just 128KB memory? Can I get through Lions' book?
That I don't know, but I do recall being unhappy whith 256KB when
trying to re-compile the kernel for 2.9BSD after an install from tape
(generic kernel).
I am looking at adding wires to the backplane to make
it a 22-bit machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and
4MB sizes).
Yep. Been there, done that.
However, I am not ready to dive in and start
modifying the qbus
backplane for 22-bit addressing just yet. So my question is:
Rather than invest in a 256KB memory board designed for the 18-bit qbus,
can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit system,
and just use the first 256KB for now?
Check the memories and peripherals handbook that covers your card
(MSV11-P or some such, IIRC). You might well be able to disable the
extra fields. The only issue I'd worry about up front is how the
board might behave in a backplane that lacks termination for the top
four address lines.
Also, is the VT103 backplane compatible with a
quad-height memory board? (It
only has dual-height cards installed at the present time).
Yes.
Parts inventory:
- VT103, with:
- 4x4 qbus backplane, 18-bit. The manual says "two H803s (2x4 connector
blocks, stacked vertically in a 4x4 configuration)". I know there are
possible issues with "straight" vs. "serpentine" slots, but I
have not
got that figured out yet on the VT103.
It's all serpentine. No "straight" slots.
- M8186 KDF11-A CPU (Newer revisions of
KDF11-A's are 22-bit capable)...
Yes. Chances are very good yours is a newer rev. They made a lot of them.
- M8029 (RXV21) floppy disk board (18-bit DMA only).
-Will this be a
problem with Unix v6 or 2.9BSD if running with 22-bit addressing?
Check the driver source. There is likely some code to handle DMA into
a low-memory buffer then a copy to user-created buffer space.
So, initially I want to run a 22-bit memory board
(M7551) in an 18-bit
VT103 qbus backplane, and access only the first 256KB of memory using
18-bit addressing. Is this possible? Thank you for your help.
It is likely to be possible - check the handbook.
-ethan
5:46 p.m.
Scott M wrote:
I recently acquired my first DEC PDP. It is a VT103
(VT100 terminal with
a PDP 11/23 inside). It came with a pair of cartridge disk drives (HEAVY!)
that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives), boxes
of manuals, 3 DEC operating systems, software, and an extra VT100.
Congratulations. My first PDP-11 was also a VT103 with a DSD 880/8 (5
MB RL01 and RX03)
and 256 KB of memory.
While the DEC operating systems are OK, I am actually
interested in using
the machine to (finally) go through "Lions' Commentary on Unix" (Unix V6),
using software downloaded from http://www.tuhs.org/. (Lions' book here):
http://www.amazon.com/dp/1573980137/
After I do that, I want to move up to Unix v7, 2.9BSD, and try other Unix
distros available for the PDP.
My concern is that the 18-bit PDP 11/23 does not have enough memory.
It currently has 128KB installed, with a maximum of 256K possible after a
memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I
can get with just 128KB memory? Can I get through Lions' book?
I run only RT-11, so I can't help with your questions.
I am looking at adding wires to the backplane to make
it a 22-bit machine,
and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and
4MB sizes). However, I am not ready to dive in and start modifying the qbus
backplane for 22-bit addressing just yet. So my question is:
Rather than invest in a 256KB memory board designed for the 18-bit qbus,
can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit system,
and just use the first 256KB for now? Also, is the VT103 backplane
compatible with a quad-height memory board? (It only has dual-height
cards installed at the present time).
I have had my VT103 enhanced to a 22 bit backplane by adding those extra
4 wires. The
work was done using wire wrap grade wire and stripping the insulation
where the wire had to
be soldered to the backplane. The extra 4 address lines on the VT103
backplane are probably
unused, at least there were on my VT103 backplane.
All of the slots in the backplane are AB / AB which allow them to accept
dual boards.
However, a quad board can also be used, in particular for the CPU and
memory.
If any dual slots are missing, then a bus grant (M9047) is required.
Since the slots
are "serpentine", the order is 1A / 1B / 2B / 2A / 3A / 3B / 4B / 4A.
To confirm, I have used a VT103 with a M8190 CPU, 4 MB of memory, DHV11 and
an RQD11-EC, all quad boards with the last being an ESDI controller.
The disk drives
used a separate PC power supply each with their own fan to keep them cool.
In general, the VT103 power supply is probably on the low side, so it is
probably
best to use as few boards as possible.
Parts inventory:
- VT103, with:
- 4x4 qbus backplane, 18-bit. The manual says "two H803s (2x4 connector
blocks, stacked vertically in a 4x4 configuration)". I know there are
possible issues with "straight" vs. "serpentine" slots, but I have
not
got that figured out yet on the VT103.
- M8186 KDF11-A CPU (Newer revisions of KDF11-A's are 22-bit capable).
http://world.std.com/~mbg/pdp11-field-guide.txt
says: "(Prior to etch rev. C, 18-bit addressing only. ...)"
I could not find revision information on the M8186 board, but "146 CA"
is stamped into one of the red plastic handles. I can email close-up
photos to anyone who wants to take a look and determine if this is a
rev C or later board capable of 22-bit addressing.
- M8043 Quad Serial board. This doc says it is 22-bit compatible:
http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardwar…
- M8029 (RXV21) floppy disk board (18-bit DMA only). -Will this be a
problem with Unix v6 or 2.9BSD if running with 22-bit addressing?
- M8208 "VT103 Maintenance Module" (Unknown if 22-bit compatible).
- Xylogics C510 (formerly called "Wizard 1") cartridge disk controller
board, with 18-bit addressing, connected to a pair CDC 9427H "Hawk"
disk drives (one disk drive is DOA, but the other is OK).
- 3rd party memory board (128KB), Christlin Industries, Inc.
So, initially I want to run a 22-bit memory board (M7551) in an 18-bit
VT103 qbus backplane, and access only the first 256KB of memory using
18-bit addressing. Is this possible? Thank you for your help.
I should think it is possible, but I would check with someone who knows.
Jerome Fine
5219
days inactive
5220
days old
6 comments
5 participants
participants (5)
-
ethan.dicks＠gmail.com -
IanK＠vulcan.com -
jhfinedp3k＠compsys.to -
pete＠dunnington.plus.com -
scott.m.18＠atsgate.com