TUHS

tuhs@tuhs.org

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6541 discussions

Re: [TUHS] Some resources for V6/PDP/SIMH newbs like me

by jnc＠mercury.lcs.mit.edu

> From: Will Senn > he is addressing an aspect that was not addressed in either of the > manual's entries and is very helpful for making the translation between > PDP-11 Macro Assembler and unix as. I'm curious - what aspect was that? Noel

7 years, 8 months

Re: [TUHS] Some resources for V6/PDP/SIMH newbs like me

by jnc＠mercury.lcs.mit.edu

> From: Will Senn <will.senn(a)gmail.com> > 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 Err, which manual are you referring to there? Not the "UNIX Assembler Reference Manual": http://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/doc/as/as I would assume, but the 'as(I)' page in the UPM? Noel

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by jnc＠mercury.lcs.mit.edu

> From: Will Senn > I'm off to refreshing my pdp-11 assembly language skills... A couple of things that might help: - assemble mboot.s and 'od' the result, so when you see something that matches in the dump of the 0th block, you can look back at the assembler source, to see what the source looks like - read the boot block into a PDP-11 debugger ('db' or 'cdb' on V6, 'adb' on V7; I _think_ 'adb' was available on V7, if not, there are some BSD's that have it) and use that to disassmble the code Noel

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by jnc＠mercury.lcs.mit.edu

> The 0th block does seem to contain some PDP-11 binary - a bootstrap of > some sort. I'll look in more detail in a bit. OK, I had a quick look, and it seems to be a modified version of mboot.s: http://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/source/mdec/mboot.s I had a look through the rest of the likely files in 'mdec', and I didn't find a better match. I'm too lazy busy to do a complete dis-assembly, and work out exactly how it's different, though.. A few observations: 000: 000407 000606 000000 000000 000000 000000 000000 000001 An a.out header, with the 0407 'magic' here performing its original intended function - to branch past the header. 314: 105737 177560 002375 Some console I/O stuff - this two instruction loop waits for the input ready bit to be set. 326: 042700 177600 020027 000101 103405 020027 000132 101002 More character processing - the first instruction clears the high bits of R0, and the next two sets of two instructions compare the contents with two characters (0101 and 0132), and branch. 444: 000207 005000 021027 000407 001004 016020 460: 000020 020006 103774 012746 137000 005007 This seems like the code that checks to see if the thing is an a.out file (note the 'cmp *r0, $0407'), but the code is different from that code in mboot.s; in that, the instruction before the 'clr r0' (at 0446 here) is a 'jsr', whereas in this it's an 'rts pc'. And the code after the 'cmp r0, sp' and branch is different too. I love the '05007' - not very often you see _that_ instruction! 502: 012700 177350 012701 177342 012711 000003 105711 Clearly the code at 'taper:' (TC11 version). Noel

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by jnc＠mercury.lcs.mit.edu

> From: Will Senn > I don't see this file in the tuhs source code index OK, here it is: http://ana-3.lcs.mit.edu/~jnc/tech/unix/s2/stp.h http://ana-3.lcs.mit.edu/~jnc/tech/unix/s2/stp1.c http://ana-3.lcs.mit.edu/~jnc/tech/unix/s2/stp2.c http://ana-3.lcs.mit.edu/~jnc/tech/unix/s2/stp3.c That MIT PWB1+ tape has so many treasures on it! (We've already seen all the early networking software.) I really must getting around to curating it, and making the whole works available. Noel

7 years, 8 months

Determining what was on a tape back in the day

by Will Senn

So, I came across this tape: http://bitsavers.trailing-edge.com/bits/DEC/pdp11/dectape/TU_DECtapes/unix6… I was curious what was on it, so I read the description at: http://bitsavers.trailing-edge.com/bits/DEC/pdp11/dectape/TU_DECtapes.txt UNIX1 PURDUE UNIX TAPES UNIX2 UNIX4 UNIX6 HARBA1 HARVARD BASIC TAPE 1 HARBA2 HARVARD BASIC TAPE 2 MEGTEK MEGATEK UNIX DRIVER RAMTEK RAMTEK UNIX DRIVER Cool, sounds interesting, so I downloaded the unix6.dta file and fired up simh - after some fiddling, I figured out that I could get a boot prompt (is that actually from the tape?) if I: set cpu 11/40 set en tc att tc0 unix6.dta boot tc0 = At that point, I was stuck - the usual tmrk, htrk, and the logical corollary tcrk didn't do anything except return me to the boot prompt. I was thinking this was a sixth edition install tape of some sort, but if it is, I'm not able to figure it out. I thought I would load the tape into v7 and look at its content using tm or tp, but then I realized that I didn't have a device set up for TU56 and even if I did, I didn't know how to do a dir on a tape - yeah, I know, I will go read the manual(s) in chagrin. In the meantime, my question for y'all is similar to my other recent questions, and it goes like this: When you received an unmarked tape back in the day, how did you go about figuring out what was on it? What was your process (open the box, know by looking at it that it was an x rather than a y, load it into the tape reader and read some bytes off it and know that it was a z, use unix to read the tape using tm, tp, tar, dd, cpio or what, and so on)? What advice would you give a future archivist to help them quickly classify bit copies of tapes :). Thanks, Will -- GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF

7 years, 8 months

The Fourth Research Edition Unix Programmer's Manual

by Diomidis Spinellis

I don't think we had the Fourth Research Edition Unix Programmer's Manual available in typeset form. I played a bit with the troff manual pages on TUHS and managed to typeset it into PDF. You can find the PDF document at https://dspinellis.github.io/unix-v4man/v4man.pdf. I modernized the old shell scripts and corrected some minor markup glitches through commits that are recorded on a GitHub repository: https://github.com/dspinellis/unix-v4man. The process was surprisingly smooth. The scripts for generating the table of contents and the permuted index are based on the original ones. The few problems I encountered in the troff source had to do with missing spaces after requests, the ^F hyphenation character causing groff to complain, a failure of groff to honor .li requests followed by a line starting with a ., and two uses of a lowercase letter for specifying a font. I wrote from scratch a script to typeset everything into one volume. I could not find a shell script for typesetting the whole manual in any of the Research Editions. I assume the process of running the typesetter was so cumbersome, error prone, and time-consuming that it was manually performed on a page-by-page basis. Correct me if I'm wrong here. Diomidis Spinellis

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by Steve Simon

It can be hard to visualise what is on a tape when you have no idea what is on there. Attached is a simple tool I wrote "back then", shamlessly copying an idea by Paul Scorer at Leeds Poly (My video systems lecturer). It is called tm (tape mark). -Steve

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by jnc＠mercury.lcs.mit.edu

> From: Arthur Krewat > For anyone reading old tapes, I implore you to attempt to read data past > the soft EOT ;) The guy who read my tape does in fact do that; you'll notice my program has an option for looking for data after the soft EOT. Noel

7 years, 8 months

Re: [TUHS] Determining what was on a tape back in the day

by jnc＠mercury.lcs.mit.edu

> From: Will Senn > I think I understand- the bytes that we have on hand are not device > faithful representations, but rather are failthful representations of > what is presented to the OS. That is, back in the day, a tape would be > stored in various formats as would disks, but unix would show these > devices as streams of bytes, and those are the streams of bytes are what > have been preserved. Yes and no. To start with, one needs to differentiate three different levels; i) what's actually on the medium; ii) what the device controller presented to the CPU; and iii) what the OS (Unix in this case) presented to the users. With the exception of magtapes (which had some semantics available through Unix for larger records, and file marks, the details of which escape me - but try looking at the man page for 'dd' in V6 for a flavour of it), you're correct about what Unix presented to the users. As to what is preserved; for disks and DECtapes, I think you are broadly correct. For magtapes, it depends. E.g. SIMH apparently can consume files which _represent_ magtape contents (i, above), and which include 'in band' (i.e. part of the byte stream in the file) meta-data for things like file marks, etc. At least one of the people who reads old media for a living, when asked to read an old tape, gives you back one of these files with meta-data in it. Here: http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/tools/rdsmt.c is a program which reads one of those files and convert the contents to a file containing just the data bytes. (I had a tape with a 'dd' save of a file-system on it, and wanted just the file-system image, on which I deployed a tool I wrote to grok 4.2 filesystems.) Also, for disks, it should be remembered that i) and ii) were usually quite different, as what was actually on the disk included thing like preambles, headers, CRCs, etc, none of which the CPU usually could even see. (See here: http://gunkies.org/wiki/RX0x_floppy_drive#Low-level_format for an example. Each physical drive type would have its own specific low-level hardware format.) So what's preserved is just an image of what the CPU saw, which is, for disks and DECtapes, generally the same as what was presented to the user - i.e. a pile of bytes. Noel

7 years, 8 months

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