[HN Gopher] LGP-30 found in basement, the same model of drum com...
___________________________________________________________________
LGP-30 found in basement, the same model of drum computer
programmed by "Mel"
Author : Lammy
Score : 237 points
Date : 2022-11-08 00:12 UTC (22 hours ago)
(HTM) web link (old.reddit.com)
(TXT) w3m dump (old.reddit.com)
| anyfoo wrote:
| I've seen tons (quite literally!) of ancient computers, but the
| sight of the LGP-30 still surprised me. When I saw it, I thought
| more along the lines of jukebox or background music system, not
| computer. I think the typefaces used, and the condition of the
| surfaces, might play a role in that.
| nerdponx wrote:
| I'm definitely used to seeing "retro" computers from the 60s
| and 70s on the Web, but _not_ from the 1950s.
|
| It's really jarring to me, to see what looks to me like "WWII
| era" or "Korean War era" styling on a _computer_ (that isn 't
| the size of an entire room). The fact that its input and output
| device looks like a traditional typewriter and not a modern
| computer keyboard/printer combo thing is also a weird mix of
| older and newer styles.
|
| It's a really interesting transitional era in design,
| technology, and culture all at once. And I feel like this
| computer is straddling both sides of all 3 transitions. It
| feels like a link to a past that is otherwise locked away in a
| handful of black-and-white photos. I love it.
|
| The PDP is also cool, if only because the colors and styling
| are so clearly "of that era". I love how chunky and rectangular
| the design feels, without seeming bulky, paired with the bright
| orange and yellow. Those switches look like they'd be really
| satisfying to flip, like the switches on the electric organ in
| my family friend's parents' basement that they had when I was a
| kid (this kind: https://i.ebayimg.com/00/s/Nzk0WDEwMjQ=/z/Vo8AA
| OSwqMtdzDYV/$...).
| nonrandomstring wrote:
| Realising this wasn't the same "drum computer" programmed by Mel
| and Kim on "Respectable" has made me feel so young again. Thanks
| old chaps.
| pantulis wrote:
| My initial thought was "Did Mel also program a drum machine?
| What a badass" Expected to see something like a Linndrum.
| maxbond wrote:
| I have a small ambition to write an LGP-30 emulator & to run
| Mel's poker code; sadly, in my poking around, while there's a
| tiny amount of Mel Kaye-authored source code archived[1] (in the
| form of scans of hand-written documents that appear to be the
| equivalent of pull requests, with one engineer writing them and
| another signing off on reviewing it) it's not very useful & is
| not from the poker program.
|
| It'd be amazing for that program is on this computer and someone
| can pull it off, but I imagine the magnetic drum memory would've
| decayed into noise by now.
|
| [1] Eg
| https://archive.org/details/bitsavers_royalPreciTable8Nov195...
| kps wrote:
| Simh supports the LGP-30.
|
| University of Stuttgart has copies of quite a few LGP-30 paper
| tapes, including Mel Kaye's blackjack.
| ftp://ftp.informatik.uni-stuttgart.de/pub/cm/lgp30/ [edited
| link]
| maxbond wrote:
| Frick yeah! That link 404s but and I don't speak German, but
| I'll look into it; thanks for the lead.
|
| ETA: As some of you might have guessed, it in fact is not
| 404, it's just accessible over FTP and not HTTP. It appears
| to be mirrored over here:
| https://www.mmnt.net/db/0/0/ftp.informatik.uni-
| stuttgart.de/...
|
| ETA2: For anyone who's interested, I had better luck with the
| Python ftplib than a command line client; despite following
| their instructions to use a - in the password, my command
| line client still froze up.
| neurostimulant wrote:
| Even the http mirror only allows to browse, not download.
| Please consider uploading the files to Internet Archive so
| other people can have easier access.
| CodeWriter23 wrote:
| The front panel on that PDP 8 though.
| nneonneo wrote:
| Ah, LGP-30! A few years back I had the chance to write some code
| for LGP-30 (emulated) as part of a CTF challenge:
| https://www.robertxiao.ca/hacking/defcon2018-assembly-polygl...
|
| It's such a weird architecture by modern standards - self-
| modifying code is the norm and you have to pay attention to the
| rotational speed of the drum. I can only imagine what programming
| on a real one must've been like :)
| timeimp wrote:
| That was a great write-up to have a squizz at.
|
| Amazing to see how many different arch's will run from 1 set of
| binary.
| markus_zhang wrote:
| Jeez that Robert guy really has a lot of talent. I don't know
| how to write the AMD64 version!
| axus wrote:
| I also enjoyed this story:
| https://www.robertxiao.ca/hacking/dsctf-2019-cpu-
| adventure-u...
| chiph wrote:
| It took me a moment - the LGP-30 is a computer that uses magnetic
| drum memory and is not a musical instrument from the 1980's.
|
| I'm curious if the ferrous oxide is still attached to the drum. I
| would suspect the heads need cleaning - being clogged with
| magnetic particles that have flaked off the drum.
| lake_vincent wrote:
| And here's a link to Story of Mel, for anyone who doesn't know
| who "Mel" is :)
|
| https://www.cs.utah.edu/~elb/folklore/mel.html
| Jedd wrote:
| Yes, user eldofever has described the challenges, and
| restoration procedure, around the drum on those beasts on that
| thread:
|
| https://old.reddit.com/r/vintagecomputing/comments/yonoa5/i_...
| cowmix wrote:
| In 1990 I bought a PDP 11/70 at a garage sale in AZ. It was big,
| heavy and sucked tons of power. I _ALMOST_ got BSD to boot on it.
| Lammy wrote:
| See also:
|
| https://www.masswerk.at/nowgobang/2019/lgp-30
|
| https://t-lcarchive.org/lgp-30/
| Blammar wrote:
| My First Computer Was A LGP-30 at age 14.
|
| 5 bit Friden Flexowriter punching paper tape for coding in
| machine language. Coding sheets. Weird hexadecimal digits
| 0-9fgjkqw (it took me a while to adapt to 0-9a-f when I first saw
| them!) Ordering instructions so they'd appear under the drum
| reader when it was time to execute them. Spending hours debugging
| code to the point where I was flagged in the weekly publication
| as the person most likely to be on the computer.
|
| The most amazing thing I ever saw on the LGP-30 was that someone
| had managed to implement floating point on it -- we got a chance
| to try it out near the end of our summer course. The second most
| amazing thing was a program to compute e to several thousand
| decimal places.
| jgrahamc wrote:
| FGJKQW makes sense because almost all the rest of the alphabet
| was used for the instruction set (one letter per instruction)
| so these were left over.
|
| For the life of me, I can't figure out why ORDVAC use KSNJFL.
| If you Google around you'll find the claim that this was
| because in figure shift mode the input teletype produced 01010
| to 01111 in binary on the tape for those letters. Except, I
| can't find a 5 level code that actually conforms to that. It's
| certainly not Baudot as some claim. And if you look at the
| manual the claim about figure shift isn't even true for the
| actual code used. https://www.ideals.illinois.edu/items/55048
| kps wrote:
| > https://www.ideals.illinois.edu/items/55048
|
| On p4 the code has KSNJFL punch binary 10-15. It starts with
| a permutation of Baudot ITA2 (notice the
| QWERTYUIOP/1234567890) to make 0-9 punch their values.
| jgrahamc wrote:
| Yes. But why that permutation? And although there is a
| relationship (like Q and 1 being on the same key) there
| isn't a relationship with Baudot or ITA2 (e.g. Q/1 isn't
| 00001 it's 11101).
| kps wrote:
| In case you're not already aware (and/or for readers who
| aren't, because I wasn't yesterday), they made
| substantial modifications to Model 15 Teletypes to get
| their chosen coding and key layout (numeric-pad-like
| rather than QWERTY), including modifying and permuting
| levers, type bars, and keycaps. It could be that KSNJFL
| was somehow most convenient in that respect, though it's
| hard to imagine.
|
| https://archive.org/details/modificationofte56mill
| jgrahamc wrote:
| Yeah. It's pretty interesting because they clearly did
| this super intentionally. As you say they moved
| everything around. Since they are using the existing
| keycaps which have Q/1, W/2 etc. they lose QWERTYUIOP but
| they've still got ASDFGHJKLZXCVBNM from which to get the
| hex digits.
|
| The one clue I haven't explored deeply is that there are
| references to ORDVAC and ILLIAC I using the same teletype
| equipment as prepared for the Institute of Advanced Study
| (IAS) Machine (i.e. von Neumann's machine). These
| machines all have the same principles and it's possible
| that these teletypes (prepared by the US Bureau of
| Standards) are the source of KSNJFL.
| [deleted]
| bewo001 wrote:
| My late father used to be a service technician with Royal McBee
| who sold the LGP-30 in Europe. Before I got my ZX-81, he gave
| me the LGP-30 manual as an introduction to programming. He had
| some stories about programmers optimizing drum memory access
| and what headaches this caused when the timing of the motor was
| slightly off.
| [deleted]
| ComputerGuru wrote:
| This is Mel: https://www.cs.utah.edu/~elb/folklore/mel.html
| ASalazarMX wrote:
| The story of Mel has its own wiki page, and Mel is identified
| as Melvin Kaye. There's even a picture of him in the sources!
|
| https://en.wikipedia.org/wiki/The_Story_of_Mel
| rob74 wrote:
| I wonder if that blackjack program still exists? Getting that
| to run again on this machine would probably get you the Nobel
| Prize for retrocomputing (if that was a thing).
| skykooler wrote:
| It appears to have been saved by the university of Stuttgart:
| https://www.mmnt.net/db/0/0/ftp.informatik.uni-
| stuttgart.de/...
| phpnode wrote:
| indeed it has been preserved, but personally I find it a
| little hard to follow: v0402k00'
| k2w8j'k3278'f3lj4'q2k98'22k78'q2qwj'22k54'22k58'
| 22k6j'332w0'f32k8'93lw0'w3lq0'g2k24'q2q8j'j2k94'
| q2k0j'22k68'22k70'22k50'l2kf8'92kq4'w2kq4'g2k68'
| f2q68'l2kk0'l2kf8'q2kq4'j2kf8'k2k88'l2kk4'k2k8j'
| 33300'f3300'56f40656'q06627q'f2q00'l8'2kk0'llw20806'
| 56l40656'56lj0656'56f40656'572j0656'56340656'563j0656'5644065
| 6'564j0656' 280j0406'l0640806'l0750806'l06j0806'q067f
| 7q'q06627q'q062f7q'q066f7q'
| l000000'800000'l0000'8000'80000004'7q7q7q7q'7wwwwwwj'400000'
| 3j6wj54j' v0402q00'
| l2k94'w3lwj'g2q24'w329j'g2qlj'l2wj4'f2q28'l2k94'
| f2q28'l2kw0'f2wq0'l2q78'22q38'22q40'l2kk0'92kw4'
| k2kk0'l2q38'q2q8j'j2q38'22q40'w2k64'g2q38'k2w8j'
| k2w8j'f2q88'332w0'f32jj'93lq0'f2k0j'2k9j'l3lk4'
| w2w8j'800g2q2j'8l000'4'8l800'32q28'f2q68'k33g4'
| 80j00'58'8l800'32q28'f2q68'k3274'33300'f3300'
| 20l87q7q'8l800'l327j'q2q8j'k327j'f2qk8'32q28'f2q68'
| g2w2j'q33g4'j33g4'92kw8'w2qf4'g2w60'80j00'l0'
| 22l6w45q' v0402w00'
| 8l800'l2w5j'q2q8j'k2w5j'32q28'f2q68'g2w3j'q3274'
| j3274'g3068'f2ww8'l33g4'92kw8'q2kw0'f2qq8'l3274'
| 92kw8'q2kw0'f2w20'l3274'92kw8'q2kw0'f2wq8''
| 33300'f3300'20l06f08'72lf2fl0'2608067q'80000'40000'92qwj'
| w2qwj'g2w90'f2qj4'2k9j'8l800'30'l33g4'g2wf4'
| f2wj0'92kw8'j33g4'w2w94'g2wg8'f2wj0'q2qf4'k33g4'
| 80j00'28'8l800'l2w5j'q2q8j'k2w5j'32q28'f2q68'
| g2w4j'q3274'j3274'92kw8'w2qf4'g3004'80j00'l33g4'
| 3f4w87wf' v0403000'
| f3074'q2qwj'g30l0'f2ww8'q2q8j'g303j'332w0'f32k8'
| 92w94'w2w94'g2ww8'8l000'l4'8l800'f2wj4'q3030'
| g304j'f302j'2llg589f'q2qwj'g302j'l3274'g3060'f302j'
| q2wj4'f2wq8'q2wj4'k3274'f2ww8'92kw8'j33g4'w2qf4'
| g30f0'33300'f3300'20300f52'7f5f7q7q'k33g4'k33g4'f3l30'
| q2q8j'g30k4'l2q8j'w327j'g30k4'33300'f3300'20300f0j'
| 726f6j64'726f6j7q'l2q78'k2w8j'f30w4'l327j'w2qwj'g3ll0'
| 33300'f3300'20302j06'6f72lf2f'7f7q7q7q'l2qf4'k33g4'l3278'
| 07q49gkj' v0403l00'
| q2q8j'k3278'f3l30'l00'33300'f3300'20305f46'5f720j06'
| q067q7q'l33g4'332g8'f3280'l3274'92kw8'j3274'w2qf4'
| g3204'33300'f3300'30l80f52'7f5fl806'606067q'k3274'k3274'
| l3274'w33g4'g3268'l3278'w2q8j'k3278'33300'f3300'
| 307f6f46'lf4f06l0'l608067q'l3278'g3lkj'j2k94'33300'f3300'
| l034087q'l2k94'332g8'f3280'33300'f3300'2q04047q'l3278'
| g3lw8'8l000'k327j'k327j'k2w5j'68'f32w4'80j00'
| j'k3278'w3278'80700'3j'f3l94'80j00'8' l9jk56j2'
| v0403200'
| f3lj4'q2q8j'g3240'l2q8j'w2w5j'g3240'33300'f3300'
| 30l80f0j'726f6j64'726f6j7q'80j00'l33g4'w2qf4'g33w4'f33q8'
| 33300'f3300'30l85f46'5f720j06'q067q7q'l3274'332g8'f3280'
| 80j00'f3l60'l3278'q2q8j'f3l74'50'wwwwwwq8''
| w2wj4'g32f0'w2wj4'g32gj'w2wj4'g32j4'80q00'24'
| q2wj4'63l0j'q32g4'232g0'8lf00'200'f3lg0'80600'
| f329j'80f00'f329j'l2w8j'q2q8j'k2w8j'l3048'63048'
| j3048'72q64'q3048'j3048'f2k2j'400'8l000'f2q78'
| 2w60k030' v0403300'
| l3lgj'933g0'f330j'w339j'g3350'f3344'7q000000'47q0000'
| 4000'3w00'80068'j'4'4'l3300'q33jj'
| f33f8'l33jj'q3300'f33q0'q33l8'j33lj'73320'93324'
| q3328'k33gj'f3338'q33l8'j33lj'73320'93324'q3328'
| k33gj'w3330'q3334''g3300'f33gj'l00'7q000000'
| l3300'f33q0'23300'f33g8'7q7q7q7q'4j'l332j'80268'
| j3334'l33lj'f33k0'4'63398'w339j'g336j'f339j'
| 233q4'f3lgj'l3278'w2q8j'k3278'l2q78'k2w8j'f3l6j'
| 00q0j242' v0403400'
| '''''''' '''''''' '''''''' ''''''''
| '''''''' '''''''' '''''''' ''''''''
| 00000000' v0403500'
| '''''''' '''''''' '''''''' ''''''''
| '''''''' '''''''' '''''''' ''''''''
| 00000000' v0403600'
| '''''''' '''''''' '''''''' ''''''''
| '''''''' '''''''' '''''''' ''''''''
| 00000000'
| suprjami wrote:
| ESR's mirror has updated footnotes:
| http://www.catb.org/jargon/html/story-of-mel.html
| ComputerGuru wrote:
| Thanks, they are worth taking twenty seconds to read!
| rhn_mk1 wrote:
| Are you trying to tell me that Mel, his program, and the
| ridiculous computer architecture he programmed for are not just
| apocryphal?!?
| causality0 wrote:
| There isn't nearly enough content about drum memory. I'd kill for
| a Technology Connections video about it.
| JoeAltmaier wrote:
| They mention a PDP 8e also in the basement.
|
| I used to program one! Then a PDP 11-34. In school.
|
| Some years after graduate school, in Los Alamos, visiting the
| Black Hole a very strange govt surplus store in a very strange
| town, I saw a bunch of old PDP 11-34 stuff along with printing
| terminals (DECWriters?) etc. Standing out in the rain. Because
| there wasn't room in that old warehouse for one more thing.
| Maursault wrote:
| LGP-30 had 113 tubes (for logic switching? or memory?) of mostly
| type 5687, which elsewhere had industrial uses and were used in
| hifi audio (I'm unsure how), but are not appropriate for guitar
| amplifiers. Apparently they take a lot of plate voltage and get
| pretty hot. I found this brief writeup[1] on them (with pictures)
| mildly interesting. They can be readily found on eBay in a wide
| variety of pricing of various brands with NOS pretty expensive,
| as usual. And there's a neat page dedicated to LGP-30 here.[2]
|
| [1] http://vinylsavor.blogspot.com/2020/12/tube-of-
| month-5687.ht...
|
| [2] http://ed-thelen.org/comp-hist/lgp-30.html
| gcanyon wrote:
| > 113 tubes
|
| Does anyone still make/sell tubes like this?
| Maursault wrote:
| I don't know if 5687 are still made, but there are tube
| manufacturers, Shuagang and Linlai in China, JJ Electronic in
| Slovak Republic, and Reflektor Corporation in Russia.[1][2]
| But 5687 are not rare.[3]
|
| [1] https://www.thegearpage.net/board/index.php?threads/curre
| nt-...
|
| [2] https://linlaiglobal.com/
|
| [3] https://www.ebay.com/sch/i.html?_from=R40&_nkw=5687
| i_am_proteus wrote:
| 5687 is a general purpose triode, with lower gain than the
| 12AX7 ubiquitous in guitar amps.
|
| They'd be useful in hifi preamps.
| monocasa wrote:
| I can fill in since I recently dug through the LGP-30
| schematics[0] on my current (incomplete) journey of designing
| my own tube based computer.
|
| Tubes on computers from this era were used almost exclusively
| as amplifiers, inverting and otherwise. [1]
|
| Inverting amplifiers are super helpful to turn the and/or gates
| you can build out of diode logic into nand/nor gates which then
| give you access to all of the other logic functions. But if you
| only need and/or for a particular circuit diode logic is much
| cheaper with much higher MTBF. [2]
|
| Non-inverting amplifiers are useful to buffer signals when the
| required current draw is too high for a single tube/diode to
| push.
|
| So in the LGP-30, you primarily see them being used as the
| inverters for the nor gates on it's flip flops, the amplifiers
| needed for the read/write heads of the drum, and
| inverters/buffers needed in the general logic. [1]
|
| And FWIW, I don't really see why it wouldn't do a good job
| within a guitar amp. It wouldn't be a good fit for the final
| output stage before the output transformer because of it's
| relatively low heft compared to a beam power tube or something,
| but it'd be a good fit for an input stage before that. They
| really don't take that much plate voltage (the LGP-30 runs them
| with a B+ of 150v). Maybe they're simply too clean of an
| amplifier and guitar amps like that distortion of tubes that
| are more prone to voltage sag?
|
| [0] If you want to follow along home, the "how is it using
| tubes?" portion of the schematics starts on page 11 here:
| http://www.bitsavers.org/pdf/royalPrecision/LGP-30/LGP-30_Sc...
|
| [1] I want to add in two places using [1] that in addition to
| what I'm saying about amplifiers, diode tubes are also used as
| rectifiers in the power supply. There'll only be a handful of
| the in each design, but because they're used in the power
| supply of pretty much every design they're still ubiquitous
| even if they don't count for much versus all tube use in these
| computers.
|
| [2] This use of germanium diodes in logic came pretty late in
| tube computers though, really in the late 50s at the cusp of
| transistorized machines. Royal Precision's next computer, the
| RCP-4000 was basically the same design as the LGP-30 but with
| tubes swapped out for transistors. Leads to some goofy
| schematic choices like the negative voltages being at the top
| of the schematic pages because it lines up better when compared
| with a tube based design.
| klodolph wrote:
| The 5687 has a low mu and high transconductance. If you put
| it on a chart with the 12AX7 and the 12AU7, the 12AU7 would
| be in the middle. The 5687 has _even higher_ transconductance
| and a little lower gain.
|
| If it ran hot, part of that was probably the fact that the
| 6.3 V heaters ran at 900 mA, instead of the 300 mA. This is a
| full 3x as much power, just for the heater.
|
| You could use it in a guitar amp, but I would probably just
| use a 12AU7 instead. The 5687 has a different pinout.
|
| > It wouldn't be a good fit for the final output stage before
| the output transformer because of it's relatively low heft
| compared to a beam power tube or something, [...]
|
| There are guitar amps out there with less powerful dual
| triodes used as output. Yes, they're low-power. There are
| amps out there using a 12AU7 for 500 mW of output power. It
| seems like such a small amount of power, but it can be loud--
| loud enough to damage your ears, loud enough to get evicted,
| not loud enough to keep up with a drummer.
| Gordonjcp wrote:
| > Leads to some goofy schematic choices like the negative
| voltages being at the top of the schematic pages because it
| lines up better when compared with a tube based design.
|
| I'm guessing this is because it was using early germanium
| transistors which would most likely be PNP. It was a long
| time before NPN transistors became the "default", because
| they were easier to make in silicon which came along later.
| monocasa wrote:
| Right on the money, they're 2N1301 germanium PNP
| transistors for the most part.
| retrac wrote:
| Probably right. It's actually still normal/correct to draw
| a PNP circuit between negative rail and ground with the
| negative supply at the top. Schematics should convey how
| the engineer thinks about the circuit, and inputs come in
| the top and left and outputs exit at the bottom/right.
| Except no one really designs PNP-oriented circuits with
| negative supply voltages these days because _eugh_.
| mikewarot wrote:
| A friend of mine got one back in the 1980s when a steel mill
| threw it out... sadly it was destroyed in a flood. It brings back
| nostalgia any time I see them mentioned.
| mozman wrote:
| Thanks to the poster for linking to old.reddit.com!
| Cthulhu_ wrote:
| Are people still hung up on 'new' vs 'old' reddit? I mean if
| they got rid of the popups and nagging to install the mobile
| app, new would be fine.
|
| Mind you, 99% of my reddit usage is through the Apollo app;
| it's probably only a matter of time before they nerf that one
| though.
| lelandfe wrote:
| > I mean if they got rid of the popups and nagging to install
| the mobile app, new would be fine
|
| Sure, but they haven't, and they won't, so it's not. They
| constantly run A/B tests that include some pretty aggressive
| variants, too. Many of those completely lock out reading
| posts until you're signed up or using the app.
| ASalazarMX wrote:
| In old Reddit you open the link, see the content, and close
| the tab. New Reddit is heavier, slower, more aggressive
| towards requiring an account, specially on mobile.
| dTal wrote:
| No, "new" would not be fine. Being forced to make an account
| to see certain content is not fine. Being shown one comment
| depth at a time is not fine. Burning vast amounts of RAM is
| not fine. It's a trash fire. Intentionally so, one suspects,
| to shepherd people towards the app. The whole reason they
| keep "old" around at all is because they _know_ that "new"
| sucks.
| robotnikman wrote:
| IIRC I think a Reddit dev commented here on HN saying that
| that was the case. Can't find it again unfortunately, but
| it was the most popular top level comment on a thread about
| Reddit
| dmm wrote:
| In old I can see seven links above the fold. In the new
| layout I see fewer than two. The new layout has way too much
| whitespace.
|
| If you mainly read reddit on touchscreen devices I can see it
| not making much a difference but on larger screens it's
| pretty annoying.
| jonjacky wrote:
| The LGP-30 made ingenious, economic use of the technology
| available in the mid-1950s.
|
| Even the CPU registers were on the drum memory. The control panel
| displayed the register contents on a small oscilloscope - it
| showed the bits as they rolled by the read head!
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