TUHS

tuhs@tuhs.org

6515 discussions

by jnc＠mercury.lcs.mit.edu

So, while bringing up V6 on a hardware PDP-11/23 with an RK11 emulator using an SD card for storage which Dave Bridgham and I are doing, I found this piece of code in main() on V6 Unix: rootdir = iget(rootdev, ROOTINO); rootdir->i_flag =& ~ILOCK; u.u_cdir = iget(rootdev, ROOTINO); u.u_cdir->i_flag =& ~ILOCK; I don't get why two separate calls to iget(), with the same arguments; why not replace the second pair of lines with: u.u_cdir = rootdir; rootdir->i_count++; What am I missing? Noel

7 years, 4 months

LSX swapping

by Paul Ruizendaal

>>> LSX has a maximum of three processes that are swapped in and out in a >>> stack-like fashion. Only one process is ever in core. > > I'm having a hard time working out how this works. If process A is swapped > out, and then B, B has to be swapped in before A can be? But only one process > is ever in core at a time? To get A in, B has to be moved out? But then B > would be the last one out, and would have to come in before A? > > Anyway, I don't understand why the OS could/would care which order processes > we swapped in - unless it's something like the 'onion skin' memory allocation > algorithm of CTSS (which also had only a single process resident at a time, > IIRC), where, when a small process had to be swapped in, and a large one was > already in, it only swapped out enough of the large one to make room for the > small one. The process could recurse, hence the name. The LSI-11 had 40KB of core. The lower 16KB held the LSX kernel, the upper 24K was for the active process. LSX has 3 process slots and 2 swap slots (on floppy!). Optionally, LSX could be built with an additional background process ("BGOPTION"), but this does not work very well. Process numbers and swap slots have a 1:1 relationship. There is a global variable, cpid, with the process number of the current process, initially zero. Upon boot, LSX will load a shell as process 0. (There is no swapper process and no init in LSX). The original LSI-11 kernel code is here: http://minnie.tuhs.org/cgi-bin/utree.pl?file=LSX/sys I can refer to source lines in the repository for my TI990 port of it: https://1587660.websites.xs4all.nl/cgi-bin/9995/artifact/b6ec9496e23efe8c When a process forks, it writes the current core image out to the corresponding swap slot (this swaps out the parent) and the core image is repurposed as the new process (i.e. cpid is incremented and the proc table filled in): https://1587660.websites.xs4all.nl/cgi-bin/9995/artifact/3617ec3245c40a69?l… The child now runs and the parent remains suspended until the child completes. Yes, this implies no pipes. The shell is modified to emulate pipes with files. When the child completes, it stores its u area / exit code in its swap slot (as it is running, the swap slot must be empty. Process 3 has a small swap slot just for this). Next LSX decreases cpid and the parent process is reloaded from its swap slot: https://1587660.websites.xs4all.nl/cgi-bin/9995/artifact/b9c07dfc5add9fc5?l… The actual swapping happens here: https://1587660.websites.xs4all.nl/cgi-bin/9995/artifact/b6ec9496e23efe8c?l… The original PDP11 source has code to compress the empty space between _end and the stack pointer, which I did not get to work properly. LSX works well enough to run the standard V6 binaries unmodified. Some need to be tweaked (e.g. table space in cpp) and the shell needed the pipe change. It can run the V6 c compiler, but not with a wild card argument: that requires 4 stacked processes (sh, glob, cc and cpp/c0/..) and LSX allows only 3. Hope the above makes it a bit more clear.

7 years, 4 months

RIP Marvin Minsky

by Dave Horsfall

We lost AI pioneer Marvin Minsky on this day in 2016 from a cerebral haemorrhage, aged 88. Amongst other things, along with John McCarthy he co-founded the MIT AI Lab, co-invented the Logo "turtle", was mentioned in Arthur C. Clarke's novel "2001: A Space Odyssey", and built the first randomly wired neural network learning machine, SNARC, in 1951. He is now thought to be cryogenically preserved as "Patient 144" at Alcor (he started cooling on 27/1/2016). -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."

7 years, 4 months

Re: [TUHS] Swapping (Was: !mail tuhs@minnie.tuhs.org)

by jnc＠mercury.lcs.mit.edu

> From: Doug McIlroy >> From: Paul Ruizendaal >> LSX has a maximum of three processes that are swapped in and out in a >> stack-like fashion. Only one process is ever in core. I'm having a hard time working out how this works. If process A is swapped out, and then B, B has to be swapped in before A can be? But only one process is ever in core at a time? To get A in, B has to be moved out? But then B would be the last one out, and would have to come in before A? Anyway, I don't understand why the OS could/would care which order processes we swapped in - unless it's something like the 'onion skin' memory allocation algorithm of CTSS (which also had only a single process resident at a time, IIRC), where, when a small process had to be swapped in, and a large one was already in, it only swapped out enough of the large one to make room for the small one. The process could recurse, hence the name. > V1 was a time-sharing system; for which LIFO swapping is > inappropriate. And I don't follow that either... V1 ran on the 11/20 without memory management hardware, though, right? (Although there's that cryptic reference to the KS11 in "Odd Comments and Strange Doings in Unix", although I've never been able to find out anything else about the KS11.) So presumably one would not have wanted more than one process resident at a time, as that decreases the odds of a buggy program trashing another process? Noel

7 years, 4 months

origin of C header files

by Wesley Parish

Hi I've just had an interesting experience, explaining C header files to a nephew programmer who didn't understand them. I pointed him in the direction of Minix as an example of a small well-engineered system which would display their use. Which raised the question: when did header files come into use? Who was the first to use header files to store common system-wide or application-wide data definitions? Was it used in any languages prior to C? Thanks Wesley Parish

7 years, 4 months

OT: Need help from a *BSD guru

by arnold＠skeeve.com

Hi. Can a modern BSD guru please contact me off-list? I have a set of related tests in the gawk test suite that consistently fail on just about every *BSD system. It has me stumped, and I'd like to see these tests working if possible. (They've been not working for quite a while. That I get no complaints from BSD users tells me that gawk isn't popular in that world, but that's another story. :-) Thanks, Arnold

7 years, 4 months

!mail tuhs@minnie.tuhs.org

by Doug McIlroy

Re: [TUHS] Kernel Sizes > I've often thought that LSX was V5 'regressed' to the concepts of > V1, which was facing similar hardware constraints. Is that a > reasonable view? > LSX has a maximum of three processes that are swapped > in and out in a stack-like fashion. Only one process is ever in core. > Is that how V1 was organized? The rocess limit was higher in V1. And V1 was a time-sharing system; for which LIFO swapping is inappropriate. So LSX seems to have "regressed" to some pre-Unix state. doug

7 years, 4 months

Re: [TUHS] Kernel Sizes

by Rudi Blom

16K kernels? Well, I came late to the UNIX world. I only remember getting a SCO UNIX 3.2V4.2 kernel onto a single 3-1/2" diskette and still have all I wanted including (with scripts on a second diskette of course :-) ). That was 25 years ago. Mind you, from there I moved to Digital UNIX /vmunix 9,613.712, Tru64 17.930.976 to HP-UX 11iv2 66.161.464 and HP-UX 11iv3 127.929.032 Of course, I also got lots more functionality I'm supposed to want and need :-) Cheers, rudi

7 years, 4 months

Kernel Sizes

by Warner Losh

For a presentation I'm doing this summer on FreeBSD, I thought it would be cool to get the kernel sizes for various old flavors of Unix. I see numbers for v5, v6 and v7 in the tuhs tree view, and it appears these versions are complete enough for me to extract the kernels themselves. However, I see nothing prior to that. The archives seem to be somewhat incomplete, but I'm wondering if people have sizes for earlier versions. Later versions are more problematic because they move to new hardware, instruction sets, etc. For this graph to be meaningful, it would need to be pdp-11 only, though I'm of the opinion more data is better than less. I'll also be extracting the different V7 commercial kernels: V7M, Ultrix and Venix and the BSD 2.x releases, but those appear to be intact enough in the archives to extract data on my own. I've heard rumors there's a SysV for the pdp-11, but I've not been able to locate images for that. I don't need the actual images, just sizes with some reference for the source of the data. It's just for one slide in the talk, so I don't want to burn a ton of time on it... The larger picture is that I've written what's effectively modprobe for FreeBSD and will be talking about it in detail. How it's like modprobe, how it's different, how all the pieces fit together, history of similar efforts, etc. Part of the driving force here is the bloated FreeBSD GENERIC kernel. Of course, I'll share the final report I'm planning on sizes with the group. Thanks for any data you can provide. Warner

7 years, 4 months

Re: [TUHS] Kernel Sizes

by Paul Ruizendaal

> A self-imposed limit of 16K held in v1, and was quite fully utilized. > When the iernel was rewritten in C, the limit (perhaps larger by then) > influenced the C compiler. More than one optimization was stimulated > by the need to keep the kernel in bounds. > > Doug The LSX kernel was kept within a self-imposed limit of 16KB as well. I've often thought that LSX was V5 'regressed' to the concepts of V1, which was facing similar hardware constraints. Is that a reasonable view? For example, LSX has a maximum of three processes that are swapped in and out in a stack-like fashion. Only one process is ever in core. Is that how V1 was organized? I realize that LSX was API compatible with V5/V6 and I don't mean 'regressed' in that sense. Paul

7 years, 4 months

Re: [TUHS] Kernel Sizes

by Doug McIlroy

> I seem to remember that at some point early on, we spent some of our > capital budget on buying another 16K bytes for the PDP-11. As I > recall, the deal was that the OS got 8K and users got 8K. I also > recall that that purchase was 20% of our capital budget for the > year... > Doug, did I remember this correctly? > Steve Things did happen that way. I don't specifically remember the numbers, but those you state have the ring of truth. Memory came in (expensive) 4K increments. When the keepers of Unix in the Charlotte wire center wanted to add 4K, their management consented only on the condition that the wizards in Research would confirm that roposed new functionality really required it. doug

7 years, 4 months

Re: [TUHS] Kernel Sizes

by Doug McIlroy

>> A self-imposed limit of 16K held in v1 > 16k words or 16k bytes? Bytes. doug

7 years, 4 months

Subject: Re: KernelSizesA self-imposed limit of 16K held in v1, and was quite fullyutilized.Subject:Re: Kernel Sizes

by Doug McIlroy

A self-imposed limit of 16K held in v1, and was quite fully utilized. When the iernel was rewritten in C, the limit (perhaps larger by then) influenced the C compiler. More than one optimization was stimulated by the need to keep the kernel in bounds. Doug

7 years, 4 months

OT - Has anyone seen / have a copy of computer lore story about a DC consolidation?

by Grant Taylor

Sorry for the off topic post. I'm hoping that someone here might have seen a (what I consider to be) a computer lore type story about a contractor that was brought in part way through a project to consolidate three DCs into one. - In the end he managed to do it early and under budget. The kicker is that they quite literally physically moved and re-connected everything the way that it was. Meaning that there were still WAN circuits (local only of course) between equipment that was previously in different DCs. I would like to find a copy of this story and save it in my archive. But I've not been able to do so. Thus I'm asking a wider audience to see if anyone might be able to give me a pointer. -- Grant. . . . unix || die

7 years, 4 months

RIP Ed Yourdon

by Dave Horsfall

We lost Ed Yourdon on this day in 2016; a computer pioneer, he helped to design the underpinnings of relational databases, and pretty much wrote the book. -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."

7 years, 4 months

Happy birthday, John Lions!

by Dave Horsfall

Dr. Prof. John Lions was born on this day in 1937; I had the pleasure of having him as one of my Computer Science lecturers in the early 70s, and he drilled into us the Principle of Least Astonishment (or POLA), better known as "why the fsck did it do that?" (but he was far too genteel to express it that way). And yes, that's my name in the credits; I helped with the proof-reading and provided the use of the high-quality printer in the CSU. You are not expected to understand this. -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."

7 years, 4 months

Scot Hacker's 1999-2001 "BeView" columns for Byte.com (BeOS)

by Arrigo Triulzi

Scot Hacker has re-published his BeOS columns for Byte. BeOS was an interesting operating system with a clear Unix inheritance built for a dual-PowerPC system, similar to the Macs of that era. http://birdhouse.org/beos/byte/ Its inheritance can be found in Haiku (https://www.haiku-os.org) Arrigo

7 years, 4 months

Some resources for V6/PDP/SIMH newbs like me

by Will Senn

All, While it's fresh, I thought I'd share some resources I've found helpful in learning about the venerable v6 as a relative newb... Learning Unix V6 in the modern era is an interesting and enormously educational experience. In the process of using it I have had to learn how to host it in a simulator (SimH in my case, but there are others), install it, communicate with it, configure it, build special files for it, attach devices to it, communicate with the devices attached to it and to SimH, build a kernel, install the kernel, boot the kernel, work with a variety of media intended to work with it, extend it, and so on. In addition, I have had to learn a bit about the PDP-11 (as arguably the most convenient architecture for learning about V6), about its architecture, its instruction set, its devices, its memory structure, and so on. None of this exploration would have been possible without the excellent work of Bob Supnik, Mark Pizzolato, and co. on the SimH pdp-11 simulator, the Simh mailing list, Warren Toomey and TUHS for making the bits available, the TUHS mailing list, PUPS, Bitsavers, and a slew of readily available documentation and texts including these notables: Setting Up Unix 6th Edition from the V6 Programmer's Manual The Unix V6 Programmer's Manual in its entirety The SimH and SimH PDP-11 Manuals A large number of blogs with SimH specific V6 installation logs The V6 Source Code and man pages (don't forget to install man - the 1bsd version works, and is superior)! The DEC PDP-11/05-10-35-40 1973 Handbook (the 11/40 handbook is not as detailed with respect to memory management) Lions's Commentary on the Sixth Edition source code Now that I'm over the beginner's hump, so to speak, I'm exploring things differently and I thought I'd share some resources that I am currently finding useful and interesting in my explorations... To bone up on assembly language, Lions's commentary is exceptionally helpful in explaining assembly as it is implemented in V6. The manual itself is really thin, and the source is a bit cryptic, for the newcomer. Lions explains the idioms used in the main source of V6. However, without a background in assembly language, Lions is pretty meaningless, so I went looking for something that was PDP specific that would bridge the gap and help me understand Lions's words. I found a number of texts that were really good. Most require a working RT11 instance to actually try out the coding examples and do the exercises (SimH and Bitsavers to the rescue): Arthur Gill - Machine and Assembly Language Programming of the Pdp-11 Charles A. Kapps and Robert L. Stafford - Assembly Language for the PDP-11 Glenn H. MacEwan - Introduction to Computer Systems: Using the PDP-11 and Pascal James F. Peters - The Digital Way: Macro-11 Assembler Programming (PDP-11) Michael G. Schneider - The Principles of Computer Organization: With Assembly Language Programming for the PDP-11 PDP-11 Processor Handbook (pretty much any edition) Thomas A. Frank - Introduction to the PDP-11 and its Assembly Language All of these are useable with a running RT11 instance. But, I think the Peters and Frank books are the standouts. Peters because all of the exercises that I have tried (dozens) have worked as printed and Frank because he is rigorous in his treatment of the subject and builds up from digital logic all the way through program execution. Frank is an excellent complement to Lions work because he explains the details that Lions assumes. To learn about digital logic, and a special thanks to Warren for his work on Crazy Small CPU, I have been introduced to logisim. It is a great playground for exploring digital logic. I had no idea that a sketchpad for digital logic simulation was available and accessible to the layperson. Logisim development stopped around 2014 and while there are a number of successors out there, I am using logisim-evolution: https://github.com/reds-heig/logisim-evolution The rabbit trails never seem to end... in order to learn how to use logisim, I went through the excellent tutorial and then went looking for a book of experiments in digital logic and found: digital computer lab workbook from 1969 http://bitsavers.trailing-edge.com/pdf/dec/handbooks/Digital_Computer_Lab_W… digital equipment corporation computer lab teacher's guide from 1968 http://www.so-much-stuff.com/pdp8/pdf/ComputerLabTeachersGuide.pdf These two are useable with very little modification as a source of digital logic exercises that work great with logisim and are related to the architectural lineage of the PDP-11. These resources fit together nicely in my pursuit to better understand digital logic, the pdp-11, assembly language, and unix v6. In sum: Source code for v6 for what really is supposed to happen in v6 operation Lions for understanding Unix V6 sources and for unix assembly language information PDP-11 Hanbook for quick reference on PDP-11 assembly language instruction set Frank for assembly language details and for details on digital logic and its relationship to the PDP-11 architecture. Logisim to test logic constructs The digital lab workbook for practice with digital logic Later, Will -- GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF

7 years, 4 months

Re: [TUHS] origin of C header files

by Lars Brinkhoff

The book "Expert C Programming" claims Alan Snyder suggested the addition of a preprocessor.

7 years, 4 months

2018: eighteen months to the Unix 50th anniversary

by Warren Toomey

Hi all, Happy New Year. As it's now only eighteen months to the Unix 50th Anniversary, I thought I'd poll you all to get an update of what is being done to celebrate the anniversary, and/or what could we organise that has not yet been organised. Cheers, Warren

7 years, 4 months

Happy birthday, C.A.R. Hoare!

by Dave Horsfall

Sir Charles Antony Richard Hoare FRS FREng was born on this day in 1934; a computer pioneer (one of the greats) he gave us things like the quicksort algorithm and ALGOLW (a neat language). -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."

7 years, 4 months

Re: [TUHS] 2018: eighteen months to the Unix 50th anniversary

by jnc＠mercury.lcs.mit.edu

> From: George Michaelson > Try this on the birth of the ICL 2900. Along the same lines, there's this: https://www.netjeff.com/humor/item.cgi?file=GenesisForProjects with its great closing line.. Noel

7 years, 4 months

Happy birthday, Donald Knuth!

by Dave Horsfall

Computer pioneer Donald Knuth was born on this day in 1938; amongst other things he gave us the TeX typesetting language, and he's still working on "The Art Of Computer Programming" fascicles (I only got as far as the first two volumes). I really must have a look at his new MMIX, too; I love learning new programming languages (I've used about 50 the last time I looked, and I'm happy to post a list for my coterie of disbelievers). -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."

7 years, 4 months

Re: [TUHS] [TUHS} 2018: eighteen months of the Unix 50th anniversary

by Doug McIlroy

> I will be happy to forward pertinent suggestions. Here's one. If Bell Labs holds some kind of symposium on the lines of the dmr memorial, how about a plenary session with TV participation from remote venues (think Berkeley/Silicon Valley and Wollongong/Sydney--a nine-hour span of time zones). Any thoughts about this or other possibilities? Doug

7 years, 4 months

Re: [TUHS] [TUHS} 2018: eighteen months of the Unix 50th anniversary

by Doug McIlroy

I don't think I'm violating anyone's confidentiality by revealing that Marcus Weldon, current president of the Labs, at the suggestion of Martin Carroll, expects the Labs to embark soon on plans to mark the occasion. I, and no doubt Martin, will keep you posted. Meanwhile I will be happy to forward pertinent suggestions. Doug

7 years, 4 months

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TUHS