FAQ on the Unix Archive and Unix on the PDP-11

Welcome to the FAQ on the Unix Archive of PDP-11 Unix material, and how to make use of it, either on a real PDP-11 or on an emulator. This FAQ doesn't cover general Unix history or politics; you will have to go elsewhere for that information.

If you have just obtained an Ancient UNIX license and want to run some old versions, go straight to the section on PDP-11 Emulators.

Last FAQ update: May 2000

Table of Contents


Introduction


Unix Source Licenses


PDP-11 Versions of Unix


Hardware


PDP-11 Emulators


Installing Unix on a PDP-11


Problem Solving

Introduction

What is the copyright/ownership status of these old versions of Unix?
The Santa Cruz Operation (SCO) own (at least): Unix research editions 1 to 7, PWB/UNIX, Mini-UNIX, 32V, System III and System V. Those parts of 2.xBSD which are derived from SCO's stuff is also copyright by SCO. Non-derived parts of anything are owned by someone else (e.g the Regents of the University of California for the BSD stuff).

None of the stuff owned by SCO is freely available, nor is it in the public domain. You must still be covered by a Unix source license in order to have legal access to this material. However, you can obtain a UNIX source for free from SCO's web site.

What's in the Unix Archive?
5th, 6th and 7th Edition Unix. All versions of 2BSD, including 2.11BSD. Some versions of 4BSD. 32V. System III for the PDP-11. Xinu. Venix. Several PDP-11 emulators. Many tools which can work with old Unix disk and tape formats. Lots of documentation and other useful information. For more details, see the sections below on PDP-11 Versions of Unix and PDP-11 Emulators.

How do I access the Unix Archive?

You first need to obtain an Ancient UNIX license from SCO's web site. Once you have clicked on the license, go to the bottom and follow the hyperlink to obtain access to the Unix Archive.

After you fill in your details, you will be emailed the access details. The go to the Unix Archive sites list to find your nearest mirror of the archive.

Once you have been granted access, you can also order the Unix Archive on CD-ROM or other media. This is done on a volunteer basis, so it may take some time. Please volunteer to help out with this effort if you can.

What happened to the early versions of Unix
The earliest complete system we have found is 6th Edition UNIX. 5th Edition has its on-line manual pages missing. We have source code to a kernel written in C from just before 4th Edition. We have two versions of the C compiler from around 3rd Edition, and we have some application binaries and application source from around 1st and 2nd Edition UNIX.

Fortunately, we do have paper copies of all the research editions of UNIX from 1st to 7th Edition, and these will be scanned in and OCR'd. We would be extremely pleased if anybody could unearth any of the first four research editions of Unix, in any format. That includes printouts!

I do have a PDP-11, can I use this old Unix software?

Yes, depending on what type of hardware you own and once you have a source license (see next section). Consult the sections on PDP-11 Versions of Unix and Hardware to determine what versions of Unix can run on your hardware.

I don't have a PDP-11, can I still use this old Unix software?

Yes, once you have a source license (see above). There are several high-quality PDP-11 emulators which will run most of the versions of Unix in the Unix Archive. Now you can read the Lions' commentary and run the software. You still need a source license. See the Section on PDP-11 Emulators for more details on the available emulators.

Unix Source Licenses

I'm covered by a Unix source license, can you give me access to the Unix Archive?

Yes. If you have a Western Electric or AT&T source license, please photocopy the pages which give the license number, name of licensed institution, and details of which versions of Unix are covered. Get the institution to draft a letter affirming that you are an employee of the institution and are covered by the source license. Then send the license details and the letter from your institution, via snail mail or fax, to:

Warren Toomey
School of Computer Science
ADFA. ACT. 2600.
AUSTRALIA.
Fax: +61 2 6268 8581

Alternatively, obtain a free SCO source license as described in the Introduction to get automatic access to the archive.

I've got the Lions' book, can you give me access to the Unix Archive?

No. The copyright on John Lions' commentary specifically states that:

None of the computer software source code contained in this publication may be copied, distributed, modified, transferred or used in any way.

Therefore, you can only read the book, and nothing else. You must still be covered by a Unix source license in order to get access to the archive.

Ok, where do I get a license from?
See the Introduction for details on how to obtain a free Unix source code from SCO.

I have the SCO license, can I get 2.xBSD?

Yes, they count as 16-bit ``successor systems''.

I have the SCO license, can I get 4.xBSD?

Yes. You need a 32V license to obtain 4.xBSD, and 32V is covered by the SCO license. Kirk McKusick is now selling a 4CD set which contains all the BSD releases from CSRG: 1BSD, 2.xBSD, 3BSD and 4.xBSD. See Kirk's web site for more details.

Some of the 4.xBSD releases on Kirk's CD set are available in the Unix Archive. We don't keep all of Kirk's CDs in the archive, because he put so much effort into writing 4.xBSD and deserves some compensation. However, if you need a specific 4.xBSD release, then please e-mail Warren and he will work something out for you.

The SCO license mentions DESIGNATED CPUs? What gives?

My contact at SCO says ``on SCO's request, you must furnish the list, but we don't demand it up front.'' I can't wait for them to ask me, I've only got emulators!

PDP-11 Versions of Unix

What versions of Unix are in the archive?

The PUPS archive contains full, bootable distributions of 5th, 6th and 7th Edition Unix, 2.9BSD & 2.11BSD, Mini-UNIX and 32V. Other versions of Unix in the archive, but which are either not complete or not bootable are PWB/UNIX, AUSAM, 2.79BSD, 2.8BSD and 2.10BSD. The archive contains some of the 4.xBSD releases as well, Ultrix-11 and System III for the PDP-11. There is also a copy of Xinu for the LSI 11/23: Xinu is not Unix, but it embodies many of the ideas in Unix.

There are several distributions of `patches' to the above systems, such as 1BSD, 2BSD, V7-addenda and V7M. Finally, there are several modified versions of Unix, such as the V6 with RL02 support from Tim Shoppa, and the heavily modified V7 from Torsten Hippe.

I have a PDP-11; which version of Unix do you recommend I run on it?

[Answered by: Warren Toomey wkt@tuhs.org]
Firstly, you need to restrict the list of choices to those flavours of Unix which will run on your PDP-11: see the next section on Hardware for details on this. Assuming you have worked that out, I would suggest the following:

Try to run 2.11BSD if possible, because it is the most modern flavour of PDP-11 Unix, and it is being supported by Steven Schultz (in his spare time). If you can't run 2.11BSD, then try 2.9BSD which is more modern than 7th Edition.

If you have a historical bent, then you can run 5th, 6th or 7th Edition Unix. These tend to be limited in the hardware that they support. I'd recommend that you use one of the PDP-11 emulators for these systems, as it will give you less heartache then trying to install it on a real -11, and you probably will get frustrated by these old systems anyway.

Hardware

What CPU, memory management, FPU, is in my PDP-11?

You'll need to know this so as to work out what versions of Unix you can run. If you don't have any DEC technical manuals about your box, try the PDP-11 FAQ at www.village.org. If that doesn't help, you might post a message in the Usenet newsgroup vmsnet.pdp-11: there are a lot of hardware-oriented people there. Be as descriptive as possible!

What hardware does 5th Edition Unix support?

[Answered by: Warren Toomey wkt@tuhs.org]
I've only ever seen V5 distributed as RK05 disk images, and we don't have the manuals so it's impossible to tell if it was distributed like this, as tapes, or both. Dennis Ritchie says that V5 isn't too much different from V6, and that most of the V6 manuals can be used for V5.

The V5 in the archive, from Dennis, expects an 11/40-style machine: 18-bit addressing with kernel and user modes and EIS, and around 40Kw of memory. You will need a line-frequency clock or a real-time clock (KW11-L). There is support for 11/45-style machines with supervisor mode in sys/conf; however, split I/D is actually used. Floating point is required to run some programs; this is FP11-B only.

The V5 kernel as distributed supports the following devices (quoted from the sources in sys/dmr):

DR11C, DC-11, DH-11, DM11-B, DN-11, DP-11, KL/DL-11, LP-11, PC-11, RS11, RK05, RP03, TC-11, TM11, VT01.

The following devices have boot code written for them:

RK03/05, rp, rk. I've got to grok the V5 mdec stuff a bit more to complete this list.

It's likely that some of the device drivers in V6 could be backported to V5 with little difficulty.

What hardware does 6th Edition Unix support?

[Answered by: Warren Toomey wkt@tuhs.org]
I've only ever seen V6 distributed as disk images, although the manuals describe how to load it from tape. It would be nice if someone recreated the tape records.

As distributed, virgin V6 expects an 11/40-style machine: 18-bit addressing with kernel and user modes and EIS, and around 96Kw of memory. You will need a line-frequency clock or a real-time clock (KW11-L). There is support for 11/45-style machines with supervisor mode in sys/conf; split I/D is supported. Floating point is required to run some programs:

UNIX only supports the 11/45 FP11-B floating point unit. For machines without this hardware, there is a user subroutine available that will catch illegal instruction traps and interpret floating point operations. (See fptrap(3)). The system as delivered has this code included in all commands that have floating point. This code is never used if the FP hardware is available and therefore does not need to be changed. The penalty is a little bit of disk space and loading time for the few floating commands.

The V6 kernel as distributed supports the following devices (quoted from the sources in sys/dmr):

DR11C, DC-11, DH-11, DM11-B, DN-11, DP-11, RP04, RS03/04, TJU16, KL/DL-11, LP-11, PC-11, RS11, RK05, RP03, TC-11, TM11, VT01, TU56, TU10,

The following devices have boot code written for them:

TU10, TU16, RP03, RP04, ht, hp, RK03/05, DECtape, TM11. I've got to grok the V6 mdec stuff a bit more to complete this list.

The Boot_Images directory has an RL02 image of V6. I haven't have a look at this yet, but it may contain kernel source for RL02 support.

What hardware does Mini-UNIX support?

[Answered by: Warren Toomey wkt@tuhs.org]
This is very interesting. Mini-UNIX is a very cut-down 6th Edition that appears to run on PDP-11s without memory management. The documentation in Mini-UNIX says:

The MINI-UNIX system running is configured to run on an 11/10 with the given disk and the console teletype (KL) and using the EIS (extended instruction set) software emulation package. emul.s contains the software emulation package to handle the extended instruction set, i.e. those instructions which are not implemented in the PDP-11/20 and PDP-11/10 processor hardware.

MINI-UNIX uses 12K words of memory for the system and 16K words for user programs. Most of the MINI-UNIX software will run with 12K words of memory, but some things require much more.

MINI-UNIX only supports the 11/45 FP11-B floating point unit. For machines without this hardware, there is a user subroutine available that will catch illegal instruction traps and interpret floating point operations.

As well, the setup documentation describes the essential differences between Mini-UNIX and 6th Edition:

There are a number of differences between the capabilities of MINI-UNIX and standard UNIX of which the user should be aware. The concept of ``groups'' is not supported in MINI-UNIX; no profiling is done in MINI-UNIX; it is not possible to interactively debug another running process in MINI-UNIX. User programs are limited to 16K words in size and the sharing of text is not possible. Pipes are not implemented in the system; rather they are implemented as ``pseudo-pipes'' in the Shell command. Thus complex commands such as:

nm a.out | grep _c | pr -3

are still possible. However the commands are executed sequentially, saving data in intermediate files. The bc command, in particular, works as in the standard UNIX system but cannot be used interactively since pipes are not implemented in the system. The source for the yacc compiler has been edited to change some table sizes to make it run in 16K words of memory.

Apart from that, I haven't given this a really good look. At the moment, the Unix Archive has Mini-UNIX on three RK05 disk images.

What hardware does 7th Edition Unix support?

[Answered by: Warren Toomey wkt@tuhs.org]
As distributed, virgin V7 expects an 11/45-style machine: 18-bit addressing with kernel, supervisor, user modes, EIS, split I/D, and around 128Kw of memory. You will need a line-frequency clock or a real-time clock (KW11-L). There is support for 11/40-style machines without supervisor mode in sys/conf. According to /usr/sys/40/README, V7 can be compiled to run ``on the 11/40, 11/60, and 11/23. It has, in fact, worked on the latter machine ... Support is included for FP11-style floating point but I can't vouch for it.'' The V7 setup document has this to say about floating-point:

UNIX only supports (and really expects to have) the FP11-B/C floating point unit. For machines without this hardware, there is a user subroutine available that will catch illegal instruction traps and interpret floating point operations. (See fptrap(3).) To install this subroutine in the library, change to /usr/src/libfpsim and execute the shell files compall and mklib. The system as delivered does not have this code included in any command, although the operating system adapts automatically to the presence or absence of the FP11.

Henry Spencer says:

It was difficult to run V7 on a non-split-I/D machine. Possible, yes, but it required a severely cut-down kernel and was really only practical as a single-user machine. The bigger utilities (f77 is the example that comes to mind) simply could not run that way.

Note that there was a bug in V7's long-divide library routines which was largely invisible on pre-44 machines but made itself quite visible on the 44 and later CPUs.

The V7 kernel as distributed supports the following devices (quoted from the sources in sys/dev):

DR11C, DC-11, DH-11, DM11-B, DN-11, DU-11, DZ11, RP04/RP06, TJU16, KL/DL-11, RF11, RK05, RP03, TC-11, TM-11.

You will also find bootable disk images (and kernel sources in Trees/V7) with suport for RL02.

The following devices are supported for the initial tape installation:

RP04/RP06, TJU16, RK05, RL02, RP03, TM11, Virtual tape driver.

The following disks have boot code written for them:

RP04/5/6, RK05, RL02, RP03.

What hardware does V7M support?

The PUPS archive contains two modifications to V7: v7appenda and V7M. The first modification came out of Bell Labs. V7M was done at DEC, and contains v7addenda. The top-level V7M README says:

UNIX/V7M SOURCE FILES

This directory contains the source files for unix/v7m, which is unix version 7 modified to support the new DEC devices. Such as, the PDP 1144, rm02/3, rk06/7, rl02, and ts11. Unix/v7m has an overlay kernel for non-separate I/D space CPU's. Unix/v7m also contains maintainability enhancements and bug fixes.

New devices (by looking in dev/) are:

RK06/7, RM02/3, RL02, RP04/5/6, ML11, RS03/04, LP11, RX02, TS11 (bootable)

What hardware does 2.9BSD support?

[Answered by: Warren Toomey wkt@tuhs.org]
The 2.9BSD setup instructions state:

This distribution can be booted on a PDP-11/23, 24, 34, 34A, 40, 44, 45, 55, 60, or 70 CPU with at least 192 Kbytes of memory and any of the following disks:

DEC MASSBUS: RM03, RM05, RP04, RP05, RP06
DEC UNIBUS: RK05, RK06, RK07, RL01, RL02,
  RM02, RP03, RP04, RP05, RP06
AED 8000 UNIBUS: AMPEX DM980 (emulating RP03)
AED STORM-II AMPEX DM980 (emulating RM02)
DIVA COMP V MASSBUS: AMPEX 9300
EMULEX SC-21 UNIBUS: AMPEX 9300, CDC 9766 (emulating RM05)
EMULEX SC-11 or SC-21 UNIBUS: CDC 9762, AMPEX DM980

The tape drives supported by this distribution are:

DEC MASSBUS: TE16, TU45, TU77
DEC UNIBUS: TE10, TE16, TS11, TU45, TU77
DATUM 15X20 UNIBUS: KENNEDY 9100 (emulating TE10)
EMULEX TC-11 UNIBUS: KENNEDY 9100, 9300 (emulating TE10)

The 2.9BSD kernel as distributed supports the following devices (quoted from the sources in sys/dev):

DR11C, DH11, DM11-B, DN-11, Diva Comp V, DZ-11, RK611/RK0[67], RJP04/RWP04/RJP06/RWP06, RS03/04, TJU77/TWU77/TJE16/TWE16, KL/DL-11, LP-11, RF11, RK05, RL01/RL02, RJM02/RWM03, RP03, TM11, TS11, RM02/03/05, RP04/05/06.

What hardware does 2.11BSD support?

[Answered by: Steven Schultz sms@moe.2bsd.com]
The 2.11BSD system can be booted on a PDP-11 with 1Mb of memory or more (the kernel would probably only require a moderate amount of squeezing to fit on machines with less memory, but it would also be very unhappy about the prospect), separate I&D, FP11B/C type of hardware floating point, supervisor mode (if networking is to be used) and with any of the following disks:

RK06, RK07
Any MSCP disk, including but not limited to: RD53, RD54, RA81, RZ2x (this also includes SCSI disks attached to SCSI<->MSCP adaptors such as the Emulex UC08 or CMD440)
RM03, RM05, RM80
RP04, RP05, RP06, RP07
Many other SMD disks, for example: CDC 9766, Fuji 160, Fuji Eagle

Other disks are supported (RX23, RX33, RX50, RD51) but are not large enough to hold a root filesystem plus a swap partition. The old restriction of using RL02 drives in pairs has been lifted. It is now possible to define a root (`a') partition and a swap partition (`b') and load at least the root filesystem to a single RL02. Discs which are too small to hold even a root filesystem (floppies for example) may be used as data disks or as standalone boot media, but are not useable for loading the distribution. Others, while listed above, are not very well suited to loading the distribution. The RK06/07 drives are hard pressed to even hold the system binaries, much less the sources.

The tape drives supported by this distribution are:

TS11, TU80, TK25
TM11, AVIV 6250/1600
TE16, TU45, TU77
TK50, TU81, TU81+, TZ30

4mm and 8mm SCSI tape drives are known to work when used with SCSI<->TMSCP adaptors.

QIC drives (such as the QIC-80, which use the DC2120 cartridges) are known NOT to work. Other SCSI tapes which correctly do `variable record mode' should work.

Although 2.11BSD contains a kernel level floating point simulator, it has never been tested. In fact it would not even compile/assemble without errors! That problem has been fixed but it is still not known if the simulator works. KDJ-11 based systems have builtin floating point so the simulator can not be tested. At the release of 2.10BSD some thought was given to the possibility of lifting the separate I&D restriction, but that thought has languished. The work will never be done. As time passes more and more programs have become almost too large even with separate I&D.

2.11BSD is known to work on the 11/44, 11/70, 11/73, 11/83, 11/84, 11/93. It should work on the 11/53 but this has not (that I know of) been tested. The 11/94 is a faster 11/84 and should also work fine. The 11/23,24,34,35,40,60 are NOT supported becuase they lack separate I/D capability. While the 11/45 does have separate I/D (and supervisor space) the 45 can not run 2.11BSD due to lack of memory (248kb maximum on the 11/45 and that is far too little).

I have a Pro 350 or 380. What can I do?
Get Venix from sunsite.unc.edu. This is a System III variant, in binary-only format.

I want to run the XXX flavour of Unix on my PDP-11, but it doesn't support my hardware. What can I do?

[Answered by: Warren Toomey wkt@tuhs.org]
At worst, you will have to write kernel device drivers and possibly bootstrap code to get Unix to use your hardware. However, you might want to look through the archive for other flavours of Unix (such as 2.9BSD and 2.11BSD), and even the modified versions of Unix (e.g the V7 modifications from Torsten Hippe) for appropriate device drivers. You may have to `port' code from one flavour of Unix to the one you wish to use.

If you are going to embark on this process, and you can't get Unix onto your PDP-11 `as is', I'd suggest you use the PDP-11 emulators plus your desired Unix flavour as a development environment to build Unix kernels and disk images with your source code modifications.

At best, the flavour of Unix you want already supports your hardware; the distribution kernel just hasn't had the code compiled in. Again, use the PDP-11 emulators plus your desired Unix flavour as a development environment to build a Unix kernel appropriate for your hardware. Then all you have to do is install the distribution plus the new kernel onto your hardware.

PDP-11 Emulators

What PDP-11 emulators are available?

There are half a dozen emulators in ftp://minnie.tuhs.org/pub/PDP-11/Sims. One runs under MS-DOS, and the others run under 32-bit Unix.

Which emulator do you recommend?
[Answered by: Warren Toomey wkt@tuhs.org]
That depends on why you need an emulator. If all you want to do is to play with these old Unixes, then nearly any of the emulators will be fine. However, if you are going to be using it as a development environment, then each emulator has its own particular advantage. Here's a summary from my own experience.

John Wilson's Ersatz emulator is the fastest emulator, and it can emulate a number of different CPU types. It also has the largest range of emulated devices. It runs under MS-DOS though, and you need a license from John if you want to use it for commercial work. If you want speed, use this one.

If you require an emulator which runs under 32-bit Unix, then I would recommend Bob Supnik's emulator, as it is fast and configurable. However, it only gives you one terminal device (the console). If you need multiple logins, then try Begemot from Joerg Micheel & Harti Brandt. It's more cumbersome than Bob Supnik's emulator, but you can telnet in to the emulator.

The above programs emulate the whole box, and are great for working with or creating disk images and tape images. However, it's hard to import/export individual files: I normally build tar images outside the emulator, and then tar vxf /dev/mt0 inside the emulator.

Another solution is to just emulate the PDP-11 user-mode, and to get the real underlying operating system to perform the system calls. The Apout emulator works this way. You can edit a file (using your normal tools) in one xterm window, and then compile it inside the emulator in another xterm window. I use this emulator for building new Unix kernels. The main drawbacks of Apout is that it only runs V6 and V7 binaries, and there is no floating point support.

Where can I get disk images for the emulators?
The directory Boot_Images in the Unix Archive contains disk images for several versions of PDP-11 Unix. Read the documentation in there to work out how to boot each disk image on the emulators.

If you are using the Apout emulator, just unpack the binaries from the appropriate version(s) of Unix in the Distributions directories in the Unix Archive.

Installing Unix on a PDP-11

How do I install the XXX flavour of Unix on my PDP-11? I do have a tape drive supported by this flavour.

Excellent! What you need to do is to get one of the PUPS volunteers to cut you a tape with a Unix installation on it and send it to you. Then you can use the standard installation instructions to load the system.

If you have the archive CD-ROM, you might even be able to create your own tape image (via one of the emulators), write the image to a real tape, and then load it as above. Let us know how you go so we can update this FAQ.

Note that, currently, 5th and 6th Edition are not in a state which can be loaded via tape. It might be possible to rectify this for V6, but no one has tried it, and you might like to volunteer!

How do I install the XXX flavour of Unix on my PDP-11? I don't have a tape drive supported by this flavour.

This is more difficult. If you have removable disk media, you might be able to convince one of the PUPS volunteers to write a distribution onto the disk pack, and ship it back to you. This might cost $$$ for postage.

If you have RT-11, see the answer to the next question.

One solution here is to pull the installation over via serial line. You're going to need a lot of patience. In Tools/Tapes/Vtserver in the archive you will find a program which installs 7th Edition Unix over a serial line from a nearby 32-bit Unix box. This hasn't been ported to V5, V6 or 2.xBSD. Again, any help we can get here would be appreciated.

Finally, if you have any other ideas or working solutions to solve this problem, please let us know!

How do I install the XXX flavour of Unix on my PDP-11? I'm currently running RT-11.

You can use the KSERVE program under RT-11, which is a cut-down Kermit client, to pull a disk image over a serial line. You will need a Kermit server at the other end, but any PC or Unix box will do here. You can obtain KSERVE in source form at ftp://minnie.tuhs.org/pub/PDP-11/ftp.dbit.com/rt11/kserve.mac or in the Unix Archive itself.

Problem Solving

I'm having a hardware problem with my PDP-11. Where can I get help?

Try the Usenet newsgroup vmsnet.pdp-11 first: there are a lot of hardware-oriented people there. You can ask the PUPS mailing list in desperation, as this is really only for questions about Unix. You might even try Mentec, who do support PDP-11 hardware (I think).

I'm having a Unix software problem with my PDP-11. Where can I get help?

Read the manuals on your version of Unix. Look through the PUPS archive (especially the Documentation section and the mail archive) for answers. Ask the PUPS mailing list, which is for people interested in these old versions of Unix: make sure you give as much detail as possible. Finally, you can try the Usenet newsgroup vmsnet.pdp-11, but the readers there tend to be more into RT-11 and RSX.


Warren Toomey
2001-05-04