TUHS

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6478 discussions

Re: [TUHS] Unix for PDP11/20 w/o mmu or paging option

by jnc＠mercury.lcs.mit.edu

> From: Clem Cole > The KS11 MMU for the 11/20 was built by CSS ... I think Noel has done > more investigation than I have. I got a very rough description of how it worked, but that was about it. > I'm not sure if the KS11 code is still there. I did not think so. No, the KS11 was long gone by later Vn. Also,I think not all of the -11/20 UNIX machines had it, just some. > The V1 work was for a PDP-7 Actually, there is a PDP-11 version prior to V2, canonically called V1. The PDP-7 version seems to be called 'PDP-7 UNIX' or 'V0'. > I'm fairly sure that the RK05, used the RK11-D controller. Normally, yes. I have the impression that one could finagle RK03's to work on the RK11-D, and vice versa for RK05's on the RK11-C, but I don't recall the details. The main difference between the RK11-C and -D (other then the implementation) was that i) the RK11-C used one line per drive for drive selection (the -D used binary encoding on 3 lines), and ii) it had the 'maintenance' capability and register (al omitted from the -D). > The difference seems to have been in drive performance. Yes, but it wasn't major. They both did 1500RPM, so since they used the same pack format, the rotational delay, transfer rate, etc were identical. The one peformance difference was in seeks; the average on the RK01 was quoted as 70 msec, and 50 msec on the RK05. > Love to see the {KT11-B prints] and if you know where you found them. They were sold on eBait along with an -11/20 that allegedly had a KT11-B. (It didn't; it was an RK11-C.) I managed to get them scanned, and they and the minimal manual are now in Bitsavers. I started working on a Tech Manual for it, but gave up with it about half-way done. > I wonder if [our V1 source] had the KS-11 stuff in it. No; I had that idea a while back, looked carefully, our V1 listings pre-date the KS11. > From: Roland Huisman > There is a KT11B paging option that makes the PDP11/20 a 18 bit > machine. Well, it allows 2^18 bytes of main memory, but the address space of the CPU is still2^16 bytes. > It looks a bit like the TC11 DECtape controller. IITC, it's two backplanes high, the TC11 is one. So more like the RK11-C... :-) > I have no idea how it compares to the later MMU units from the > software perspective. Totally different; it's real paging (with page tables stored in masin memory). The KT11-B provides up to 128 pages of 512 bytes each, in both Exec and User mode. The KT11-C, -D etc are all segmentation, with all the info stored in registers in the unit. > I wonder is there is some compatibility with the KT11-B [from the KS11] I got the impression that the KS11 was more a 'base and bounds' kind of thing. Noel

3 years, 7 months

Unix for PDP11/20 w/o mmu or paging option

by Roland

Hello Unix fanatics, I have a PDP11/20 and I would love to run an early Unix version on it. I've been working on the hardware for a while and I'm getting more and more of the pieces back online again. The configuration will be two RK05 hard disks, TU56H tape, PC11 paper tape reader/puncher and a RX01 floppy drive. Unfortunately I don't have a MMU or paging option. But it seems that the earliest versions of Unix do not need the extra memory. Does anyone have RK05 disk images for these early Unix versions? That would be a great help. Otherwise it would be great to have some input about how to create a bootable Unix pack for this machine. A bit about the hardware restoring is on the vcfed forum:https://www.vcfed.org/forum/forum/genres/dec/78961-rk05-disk-drive-ve… Booting RT11 from RK05https://youtu.be/k0tiUcRBPQATU56H tape drive back onlinehttps://youtu.be/_ZJK3QP9gRA Thanks in advance!Roland Huisman

3 years, 7 months

RegExp decision for meta characters: Circumflex

by markus schnalke

Hoi, I'm interested in the early design decisions for meta characters in REs, mainly regarding Ken's RE implementation in ed. Two questions: 1) Circumflex As far as I see, the circumflex (^) is the only meta character that has two different special meanings in REs: First being the beginning of line anchor and second inverting a character class. Why was it chosen for the second one? Why not the exclamation mark in that case? (Sure, C didn't exist by then, but the bang probably was used to negate in other languages of the time, I think.) 2) Symbol for the end of line anchor What is the reason that the beginning of line and end of line anchors are different symbols? Is there a reason why not only one symbol, say the circumflex, was chosen to represent both? I currently see no disadvantages of such a design. (Circumflexes aren't likely to end lines of text, neither.) I would appreciate if you could help me understand these design decisions better. Maybe there existed RE notations that were simply copied ... meillo

3 years, 7 months

Re: [TUHS] desiderata

by Douglas McIlroy

You can check the Computer History Museum's holdings on line. If they don't have the documents already, they would probably like them. The Living Computer Museum in Seattle had a working blit on display. If they don't already have the manual, I'm sure they would love to have one. Alas, their website says they've "suspended all operations for now", a result of the double whammy of Covid and the death of their principal angel, Paul Allen.

3 years, 7 months

desiderata

by Andrew Hume

more garage cleaning this last weekend. i came across some memorabilia from my time at Bell Labs, including a lovely article titled The Electrical Properties of Infants Infants have long been known to grow into adults. Recent experiments show they are useful in applications such as high power circuit breakers. Not to mention a lovely article from the “Medical Aspects of Human Sexuality” (July 1991) titled “Scrotum Self-Repair”. the two items are 1) “Documents for UNIX Volume 1” by Dolotta, Olson and Petrucelli (jan 1981)” 2) The complete manual for the Blit. this comes in a blue Teletype binder and includes the full manual (including man pages) and circuit diagrams. i’d prefer to have them go to some archival place, but send me a private email if you interested and we’ll see what we can do. andrew

3 years, 7 months

desiderata

by Paul Ruizendaal

I’d be interested in a scan of the Blit schematics, and it seems that a few others might be as well: https://minnie.tuhs.org/pipermail/tuhs/2019-December/thread.html#19652 https://github.com/aiju/fpga-blit (for clarity: I’m not ‘aiju') Paul > Message: 1 > Date: Wed, 8 Sep 2021 01:29:13 -0700 > From: Andrew Hume <andrew(a)humeweb.com> > To: The Eunuchs Hysterical Society <tuhs(a)tuhs.org> > Subject: [TUHS] desiderata > Message-ID: <34E984D3-AD92-402D-9A9C-E84B6362DF77(a)humeweb.com> > Content-Type: text/plain; charset=utf-8 > > more garage cleaning this last weekend. [...] > 2) The complete manual for the Blit. this comes in a blue Teletype binder and includes > the full manual (including man pages) and circuit diagrams. > > i’d prefer to have them go to some archival place, but send me a private email > if you interested and we’ll see what we can do. > > andrew

3 years, 7 months

Is it time to resurrect the original dsw (delete with switches)?

by Jon Steinhart

I recently upgraded my machines to fc34. I just did a stock uncomplicated installation using the defaults and it failed miserably. Fc34 uses btrfs as the default filesystem so I thought that I'd give it a try. I was especially interested in the automatic checksumming because the majority of my storage is large media files and I worry about bit rot in seldom used files. I have been keeping a separate database of file hashes and in theory btrfs would make that automatic and transparent. I have 32T of disk on my system, so it took a long time to convert everything over. A few weeks after I did this I went to unload my camera and couldn't because the filesystem that holds my photos was mounted read-only. WTF? I didn't do that. After a bit of poking around I discovered that btrfs SILENTLY remounted the filesystem because it had errors. Sure, it put something in a log file, but I don't spend all day surfing logs for things that shouldn't be going wrong. Maybe my expectation that filesystems just work is antiquated. This was on a brand new 16T drive, so I didn't think that it was worth the month that it would take to run the badblocks program which doesn't really scale to modern disk sizes. Besides, SMART said that it was fine. Although it's been discredited by some, I'm still a believer in "stop and fsck" policing of disk drives. Unmounted the filesystem and ran fsck to discover that btrfs had to do its own thing. No idea why; I guess some think that incompatibility is a good thing. Ran "btrfs check" which reported errors in the filesystem but was otherwise useless BECAUSE IT DIDN'T FIX ANYTHING. What good is knowing that the filesystem has errors if you can't fix them? Near the top of the manual page it says: Warning Do not use --repair unless you are advised to do so by a developer or an experienced user, and then only after having accepted that no fsck successfully repair all types of filesystem corruption. Eg. some other software or hardware bugs can fatally damage a volume. Whoa! I'm sure that operators are standing by, call 1-800-FIX-BTRFS. Really? Is a ploy by the developers to form a support business? Later on, the manual page says: DANGEROUS OPTIONS --repair enable the repair mode and attempt to fix problems where possible Note there’s a warning and 10 second delay when this option is run without --force to give users a chance to think twice before running repair, the warnings in documentation have shown to be insufficient Since when is it dangerous to repair a filesystem? That's a new one to me. Having no option other than not being able to use the disk, I ran btrfs check with the --repair option. It crashed. Lesson so far is that trusting my data to an unreliable unrepairable filesystem is not a good idea. Since this was one of my media disks I just rebuilt it using ext4. Last week I was working away and tried to write out a file to discover that /home and /root had become read-only. Charming. Tried rebooting, but couldn't since btrfs filesystems aren't checked and repaired. Plugged in a flash drive with a live version, managed to successfully run --repair, and rebooted. Lasted about 15 minutes before flipping back to read only with the same error. Time to suck it up and revert. Started a clean reinstall. Got stuck because it crashed during disk setup with anaconda giving me a completely useless big python stack trace. Eventually figured out that it was unable to delete the btrfs filesystem that had errors so it just crashed instead. Wiped it using dd; nice that some reliable tools still survive. Finished the installation and am back up and running. Any of the rest of you have any experiences with btrfs? I'm sure that it works fine at large companies that can afford a team of disk babysitters. What benefits does btrfs provide that other filesystem formats such as ext4 and ZFS don't? Is it just a continuation of the "we have to do everything ourselves and under no circumstances use anything that came from the BSD world" mentality? So what's the future for filesystem repair? Does it look like the past? Is Ken's original need for dsw going to rise from the dead? In my limited experience btrfs is a BiTteR FileSystem to swallow. Or, as Saturday Night Live might put it: And now, linux, starring the not ready for prime time filesystem. Seems like something that's been under development for around 15 years should be in better shape. Jon

3 years, 7 months

Who said ...

by arnold＠skeeve.com

... DEC Diagnositcs would run on a beached whale ? Anyone remember and/or know? (It seems to apply to other manufacturer's diagnostics as well, even today.) Thanks, Arnold

3 years, 8 months

A language question

by Richard Salz

I hope that this does not start any kind of language flaming and that if something starts the moderator will shut it down quickly. Where did the name for abort(3) and SIGABRT come from? I believe it was derived from the IBM term ABEND, but would like to know one way or the other.

3 years, 8 months

Re: [TUHS] Who said ...

by norman＠oclsc.org

Clem Cole: I believe the line was: *"running **DEC Diagnostics is like kicking a dead whale down the beach.*" As for who said it, I'm not sure, but I think it was someone like Rob Kolstad or Henry Spencer. ===== The nearest I can remember encountering before was a somewhat different quote, attributed to Steve Johnson: Running TSO is like kicking a dead whale down the beach. Since scj is on this list, maybe he can confirm that part. I don't remember hearing it applied to diagnostics. I can imagine someone saying it, because DEC's hardware diags were written by hardware people, not software people; they required a somewhat arcane configuration language, one that made more sense if you understood how the different pieces of hardware connected together. I learned to work with it and found it no less usable than, say, the clunky verbose command languages of DEC's operating systems; but I have always preferred to think in low levels. DEC's diags were far from perfect, but they were a hell of a lot better than the largely-nonexistent diags available for modern Intel-architecture systems. I am right now dealing with a system that has an intermittent fault, that causes the OS to crash in the middle of some device driver every so often. Other identical systems don't, so I don't think it's software. Were it a PDP-11 or a VAX I'd fire up the diagnostics for a while, and have at least a chance of spotting the problem; today, memtest is about the only such option, and a solid week of running memtest didn't shake out anything (reasonably enough, who says it's a memory problem?). Give me XXDP, not just the Blue Screen of Death. Norman Wilson Toronto ON

3 years, 8 months

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