[HN Gopher] PDP-11 Booting
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PDP-11 Booting
Author : rdpintqogeogsaa
Score : 166 points
Date : 2021-12-11 15:28 UTC (7 hours ago)
(HTM) web link (trmm.net)
(TXT) w3m dump (trmm.net)
| not2b wrote:
| I am old enough to remember those days; got a summer job when I
| was in college at a lab that had lots of PDP-11s in, I think,
| 1980. Some of them didn't have boot ROMs and you had to toggle in
| the bootstrap program from the front panel every time (only about
| a dozen instructions).
| DrTung wrote:
| PDP 11/34 had a bootrom and an octal keyboard, which is kind of
| cheating.
|
| I grew up using the older PDP 11/45 where you had to key in
| (using binary toggles) a boot program. Or, the way I did it,
| manually enter write address and byte count to the RK05 disk
| controller (memory mapped I/O) then writing a "01" Go command to
| RK05's command register and watch the RK05 disk activity light
| flicker briefly. Voila, RT11 was loaded. (This worked because on
| the PDP 11/45 DMA transfers from disk to memory worked also in
| CPU Halt mode.)
| p_l wrote:
| DMA transfers should work on all PDP-11 that kept memory on the
| same bus as I/O (most of them, iirc, I think separate side bus
| for memory happened with VAX Q-Bus models?)
| retrac wrote:
| Boot ROMs for the early PDP-11s could be pretty nifty in their
| own right though. This is the first version of I believe the
| RX01 floppy disk boot code. 32 sixteen-bit words:
| https://www.cca.org/blog/20120222-Diode-Matrix.shtml User-
| editable!
|
| By the time of the PDP-11/34 things were much more integrated
| though. Mask IC ROMs. The front panel/interactive serial
| debugger were actually controlled by an Intel 8008
| microprocessor. You needed a computer just to boot the computer
| even then.
| tomcam wrote:
| Binary toggle switches? Luxury. In my day we didn't have binary
| toggle switches. We had to quickly touch raw wire leads to each
| other in the right sequence, flawlessly, every time. And we
| were damn grateful of it.
| dboreham wrote:
| If your -45 had core memory, the bootloader could be toggled in
| one then left in place for subsequent reboots after power off.
| smoyer wrote:
| We had a PDP 11/4 with core memory that ran a TruDrill CNC
| PCB drill. The bootloader was in ROM and if the core memory
| became corrupt you had to reload it with the same paper tape
| reader that read the G-code.
| walshemj wrote:
| I had to do this a couple of times for our 11/40 (also running
| RT11) - the was a printed cheat sheet of the OCD (octal codded
| decimal) you had to toggle in then hit the load to advance to
| the next location.
| breput wrote:
| I couldn't find any good videos of toggling in a bootloader on
| a real PDP-11, but here is one on a PiDP-11 emulator:
| https://www.youtube.com/watch?v=31vrju0BMQc
| ghostly_s wrote:
| well this is disappointing..."binary toggles" had me
| picturing a single 3-way toggle switch where you manually
| entered ones and zeroes.
| breput wrote:
| That is exactly what is going on but you don't need 3 way
| toggle.
|
| Down is 0 and up is 1, you load all of the values in like a
| shift register but in parallel, then write/act upon them.
| DrTung wrote:
| Yes the data bits were 2-way toggles, but one important
| switch was a 3-way toggle: the Examine (press down) and
| Deposit (press up) switch.
| breput wrote:
| On the 11/70, Deposit was the only switch that toggled up
| (other than the light test switch). That is a nice safety
| feature so you don't accidentally toggle Continue or
| other action switches.
| cyberferret wrote:
| Memories! One of the things I had to do in my first ever job was
| swap the backup discs in a Vax PDP-11 that ran a big
| pharmaceutical inventory system. All that time waiting for those
| huge discs to dismount and re-mount...
| kingcharles wrote:
| Someone needs to write a Y2K patch...
| donio wrote:
| http://www.eskimo.com/~nickz/dec.html
| anonymousiam wrote:
| I remember booting RT-11 on a DEC PDP/11 clone (LSI-11). You
| would turn it on (along with the Lear Siegler ADM-3A [or
| equivalent] terminal), and since it did not come with a hard-disk
| by default, you would insert the (8") boot floppy, and type
| 177170L at the (ROM) monitor prompt. The octal address was
| followed by a "L" which immediately caused the monitor to jump to
| the boot loader (also in ROM). After about five minutes, RT-11
| would be up and running (just as shown on the terminal in the
| fine article).
| foobiekr wrote:
| my godfather had an H-8 and you had to bootstrap it via the
| keypad as well
|
| kind of a charming way to learn, at a very very young age, how
| booting worked
|
| all to play colossal cave
| jshprentz wrote:
| At a summer job in 1973, we used carved wood sticks to quickly
| set the toggle switches for the bootloader.
| wazoox wrote:
| Here is a PDP-11 booting UNix v6:
| https://www.youtube.com/watch?v=9wFJL9inunQ
| djweis wrote:
| My eyesight is getting worse but is that person typing nude?
| Y_Y wrote:
| Certainly not!
|
| He's wearing a watch.
| Tsiklon wrote:
| I can see trouser pockets! either that or they're wearing a
| holster in the nude - which is a whole other ballgame
| entirely.
| cptnapalm wrote:
| Did you really have to use "ballgame"?
| guerrilla wrote:
| That thing needs some serious retrobrighting.
| wazoox wrote:
| IIRC the VT-100 was naturally more yellow-brown than beige.
| hazeii wrote:
| Brand-new they were pretty white (and gray)
| mmastrac wrote:
| If you want to play the original Adventure without the PDP-11
| (though not nearly as authentic), I ported it to the web here:
| https://grack.com/demos/adventure/
| pkaye wrote:
| Nicely done with the CRT look.
| mmastrac wrote:
| Thanks! You can see the VT220 I modelled it off here: https:/
| /github.com/mmastrac/adventure/blob/master/com.grack....
|
| I'm not really a front-end person so I just hacked on
| gradients until I could make it look just right.
| WalterBright wrote:
| I added a 6Mb hard disk drive to my H11. This required building
| an interface card, and writing the device driver for it.
|
| I used as a model the device driver for the floppy drive. I was
| rather amazed at how it worked - it was loading instructions into
| memory as it was executing the previous instruction just loaded.
| The instructions were also simultaneously handling two
| independent values in the upper and lower bytes. A marvel of
| compactness.
| tmearnest wrote:
| This is so cool. I want to see posts like this for other old
| school minicomputers and mainframes!
| nobleach wrote:
| Every once in awhile https://www.reddit.com/r/vintagecomputing/
| has some good stuff.
| manbart wrote:
| Also https://www.Reddit.com/r/retrobattlestations
| aasasd wrote:
| Off-topic: with a bunch of vintage 'booting a computer' stuff
| lately on HN and in my YT recommendations, I keep remembering
| what I once read about an old trick for 'faster booting': on
| bootup, the computer displayed a static screenshot taken before
| the shutdown (or rather to-disk suspension, apparently)--and
| while the user themselves tried to remember what they were doing
| the day before, the machine actually loaded programs into the
| memory. Only after that the cursor started blinking. Since after
| turning on the power the user received fast(er) feedback which
| kept them occupied, they perceived the bootup as much quicker
| than it actually was.
|
| Only, I don't remember what computer that was--probably paid more
| attention to the UX-design side at the time. If anyone knows, I'd
| be grateful for the reference, so I could finally file this
| properly among my pile of tech trivia.
| leeoniya wrote:
| i remember that on windows 95 (and maybe later) the login wav
| sound that played for 2s seemed to actually blocked everything
| else.
|
| simply disabling the login sound made the sign-in-to-desktop
| significantly faster.
| [deleted]
| philipkglass wrote:
| You may be thinking of the Canon Cat. This feature is mentioned
| in passing here:
|
| https://method.ac/writing/work_journal/method-draw-loading.h...
| aasasd wrote:
| TIL Raskin actually got to kinda implement his ideas of a
| text-driven interface--of which Macintosh was pretty much the
| opposite (coincidentally it's said that Mac's interface was
| largely redesigned after Raskin left the project).
|
| > _Instead of using a traditional command line interface or
| menu system, the Cat makes use of its special keyboard, with
| commands being activated by holding down a "Use Front" key
| and pressing another key._
|
| Afaik the original concept called for entire commands being
| typed in while holding the special key--which suggests that
| Raskin didn't have much consideration for touch typing--a
| bizarre attitude for a text-based interface.
| CamperBob2 wrote:
| _Only, I don 't remember what computer that was_
|
| Didn't the iPhone developer guidelines call for this to be done
| by individual apps at one point, in lieu of splash screens?
| hazeii wrote:
| The LSI-11 and 11/23 jumped to 173000 at startup, so (re)booting
| them was just hit halt on the front panel and then enter
| '173000G' in ODT (the built-in octal debugger). If necessary, it
| would only take a minute or two to type in a bootstrap somewhere
| in RAM and execute (my boss at the time could do that faster
| across the toggle keys on the front panel of his larger PDP-11
| than I could type it in).
|
| I coded several bootstraps for PDP-11/23's, managed to get 4
| different devices (DX,DY 8" disks, MX 5.25" and MZ 3.5" disks)
| complete with CLI into 256 words (2x256 byte OTP ROMs). Careful
| coding time, since one had to send the listing off to someone who
| could burn the ROMs and post them back.
| guerrilla wrote:
| > my boss at the time could do that faster across the toggle
| keys on the front panel of his larger PDP-11 than I could type
| it in
|
| This is exactly what I waned to hear after watching the video
| of toggling posted below. I thought to myself there must have
| been people who could have done that in two seconds, but then I
| kind of doubted it because I didn't know how much rebooting was
| really done.
| [deleted]
| cesaref wrote:
| Yeah, I had an LSI-11/23 when I was a student, with dual 8 inch
| drives and a Fujitsu drive (not an Eagle, it was 160Mb if I
| remember). This was all cobbled together equipment, but lots of
| fun trying to get it to work.
|
| My bootstrap code loaded the first block from a floppy which
| had the boot code on it. The result was much easier to type,
| and I ended up with that boot code as a script so my much more
| powerful Amiga I was using as a terminal emulator could replay
| the boot code to start the machine.
|
| Happy days!
| anthk wrote:
| You can play ADVENT under the BSD-games package.
|
| Also, there's a good ZMachine port (several of them). Look out
| for advent.z5.
| cbm-vic-20 wrote:
| That ASR-33 Teletype comes in handy if your PDP-11 doesn't have a
| boot ROM: toggle the first stage bootloader into the panel, load
| your tape into the reader, and let 'er rip.
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(page generated 2021-12-11 23:00 UTC)