Enter this command to bork your machine

September 17, 2015 11:28 AM

Here is some information on the "Killer Poke" of the Commodore PET 2001 computer, an infamous command that could actually damage hardware, by causing its monitor to lose sync. Like this.

The PET had an integrated monitor built into the unit. The way the machine was designed, updating the display was a costly operation in terms of processor time. Early versions of the machine had an unsupported command the user could enter, POKE 59458,62, that would greatly increase the speed at which it could update text.

Later versions of the machine changed the hardware in such a way that, if the user used this command, it would cause the monitor to lose sync and word is, if left too long, could damage it.

posted by JHarris (63 comments total)

The PETs we had in grade school were my first computers. I may or may not have tried this when we discovered the trick in a magazine. Mr Marjerison couldn't prove it then, and you can't prove it now! Ha!

There was another one you could use to gronk the two 5 1/4" floppy disk motors in the CBM 4040 modules to make a kind of primitive beatboxer. Not that I'd know the specifics of the 6502 assembly for that either (anymore, at least).
posted by bonehead at 12:00 PM on September 17, 2015 [3 favorites]

Does anyone remember the olden days, when there were computer magazines that had programs you could key into BASIC? In theory, these programs should have been cross-platform; in practice, they all made use of PEEK and POKE commands, so each program was recommended only for particular computers or product lines.

Anyway, long story short, I did something like this after keying in and running a game called "CASTLES" for another machine on an old TRS-80. It didn't seem like it damaged the computer or old b&w TV I was using as a monitor, but boy did it screw with the video output.
posted by infinitewindow at 12:00 PM on September 17, 2015 [6 favorites]

I remember there was a BASIC program every month in Enter Magazine.
posted by Chrysostom at 12:10 PM on September 17, 2015 [8 favorites]

This reminds me of the Chess Champion MK I chess computer that my dad bought in the early 80s. It's really a marvel of crappiness, even by the standards of the time. For instance, it didn't check on the legality of moves that users entered, so you could actually perform an illegal move, play without kings etc. The weirdest thing was that the manual contained a warning not to press any keys while the computer was "thinking". (If you read German, the manual is actually unintentionally hilarious.) My brother, who must have been around 16 at the time and in constant pubescent opposition to my dad, couldn't believe this. And then one time he did do it and pressed a button while the computer was working. Sure enough, the computer died on the spot. After 30+ years, both my brother and I will hear about that this any time we want to do anything on my dad's PC.
posted by tecg at 12:12 PM on September 17, 2015 [16 favorites]

Yep. I was aC64>128 nerd so it was Compute! stuff all the way down for me. So many DATA lines. Ugh.
posted by mintcake! at 12:13 PM on September 17, 2015 [17 favorites]

When I was in college, we had a fellow named Kirk who figured out that if you pushed the grey reset button on the back of a DECstation repeatedly, you could sometimes get it to give access to protected memory when it restarted. This was, needless to say, not covered by manufacturer's warranty and he did it on the wrong machine once, which led to some acrid smoke, which led to "Kirking" a machine becoming a catchphrase synonymous with electric death.

My own method of choice was something of an accident. One day, for reasons known only to myself, I decided to run a little script on one of our machines. The precise syntax is lost to history, but it pseudocoded like this:

cd /temp;
while 1 {
yow > $1;
mkdir $1;
cd $1;
}

yow was, of course, the Zippy the Pinhead fortune file generator. while 1 {whatever} was a loop whose condition could never fail, so it would go on forever or until the user hit CTRL-C to halt the process. I decided that a pathological directory like /temp/All life is a blur of Republicans and meat!/OSMONDS! You are all OSMONDS! Throwing up on a freeway at dawn/A bowling ball full of drugs/ etc. would freak out the next person who happened to use that machine, so I set up the loop intending to stop after a minute or so.

Someone distracted me with a lengthy question, and I came back not to a screen full of windows, but to a grey screen. I rebooted it -- grey screen. I power-cycled it -- grey screen. Uh oh.

I summoned IT, who were also unsuccessful at reviving it. One of their drones spent THREE DAYS fixing the machine, as this runaway mkdir loop from hell had apparently overwritten the kernel and it required complete reimaging, or so I was told. On day two I happened to do some work in the same lab, and about once an hour he turned and glared at me and snapped "HOW could this have been an accident?" I just shrugged.
posted by delfin at 12:26 PM on September 17, 2015 [35 favorites]

I used to key in programs in BASIC that I would find in Byte magazine and another magazine called Kilobaud - into my MITS Altair 8800, which I still own, via my LSI ADM-3A terminal, which I still own. That was when I was about 14 or 15 years old.
posted by Yosemite Sam at 12:35 PM on September 17, 2015 [4 favorites]

I'm pretty sure if I dug through my mom's attic I could still find several rolls of yellow paper tape - secured by long since rotted rubber bands - punched with BASIC programs I wrote on a teletype terminal at my high school that connected by analog modem (i.e., cups you dropped a phone handset into) to a Digital PDP-11 at another school a ways down the road.

It had no screen, only paper output on a big roll you tore off when you were done. And you could punch your program onto a tape punch/reader on the side. We couldn't use it on Thursday afternoon because that was when the cafeteria staff used it to order food for the following week.

And of course I once set it up to print some stupid damn thing on an endless GOTO loop and walked away. We all did.
posted by Naberius at 12:49 PM on September 17, 2015 [2 favorites]

In the very early 2000s I was the editor and staff of an underfunded internet magazine (magazine about the internet, not on the internet, for you whipper-snappers out there) called Crazynet. Our second issue was going to be a retro special including a cover-splash for 'WIN A ZX81!' (I'd found a dealer who still had some new-in-box) and at least one type-in listing.

See I'd made the acquaintance of a genius called Moose, who had come up with the idea of a listing that you'd type into the Notepad of your Windows machine, save, rename it with a .zip extension, and unzip it into something four or five times larger than the information you'd typed in.

Then the publishing company went bust two days before the second issue was due to go to press, and it never came out. In a life of regrets, that's one of my big ones.
posted by Hogshead at 12:52 PM on September 17, 2015 [9 favorites]

"Killing Poke?"

Is that where Joker hacks Facebook's poke feature?
posted by symbioid at 12:53 PM on September 17, 2015 [7 favorites]

via the linked video - pac man and invaders on a PET

More 8-bit deliciousness, thanks JHarris.
posted by marienbad at 12:59 PM on September 17, 2015

The best part of this was watching someone who had forgotten the specific address enter poke after poke with escalating levels of hormonally-infused frustration while we fed them wrong answers.

Then the librarian would flick the power switch to punish us and everybody in the lab who wasn't screwing the pooch would lose hours worth of work.
posted by CynicalKnight at 1:00 PM on September 17, 2015

The TRS-80 Color Computer had the "high speed poke" (POKE 65495 if I remember correctly) and rumor had it if you let it run too long it would heat up your CPU (the 6809) and damage it but I don't think anybody actually ever had that happen, they just knew a friend of a friend who did it.

I had a bulletin board (a cork one, not the modem kind) over my computer with 3x5 index cards tacked onto it with all the useful PEEK and POKE commands written on them, because I was cool like that.
posted by bondcliff at 1:00 PM on September 17, 2015 [1 favorite]

"Killing Poke?"

Is that where Joker hacks Facebook's poke feature?

Actually, it is where a love like blood a love like blood, the fearless come and the act is done.
posted by srboisvert at 1:14 PM on September 17, 2015 [6 favorites]

Yes, UK mags like Computer & Video games were full of type-in programs for all the 8-bits. Nothing like typing in two pages of Commodore 64 DATA statements, where 1 wrong number would cause the program not to run.
posted by GallonOfAlan at 1:16 PM on September 17, 2015 [3 favorites]

We had Commodore PETs in my grade school as well.


I think it put me off computing for another four years.
posted by TheWhiteSkull at 1:17 PM on September 17, 2015 [1 favorite]

Remember the movies made from PET graphic characters? Little me was blown away when I first saw one. A movie! On a computer screen!
posted by Joe in Australia at 1:22 PM on September 17, 2015

>which led to some acrid smoke, which led to "Kirking" a machine becoming a catchphrase synonymous with electric death.

Do not let this guy near a starship!
posted by AGameOfMoans at 1:30 PM on September 17, 2015 [2 favorites]

Does anyone remember the olden days, when there were computer magazines that had programs you could key into BASIC? In theory, these programs should have been cross-platform; in practice, they all made use of PEEK and POKE commands, so each program was recommended only for particular computers or product lines.

The reason all these programs used POKE and DATA commands was because the BASIC interpreter (on the C64 at least) was painfully slow for running a program directly from BASIC. Programs POKEd directly into machine code ran in a flash.

I remember writing a BASIC program to draw a Sierpinsky Triangle using the Chaos Game technique. It took a few minutes to fill in the pixels for the whole pattern. I later re-wrote the program in Assembler and the finished pattern popped up in milliseconds.
posted by rocket88 at 1:30 PM on September 17, 2015 [3 favorites]

Oh - and I have a nice looking and fully working Commodore Pet 2001 in my living room right now. It was the first desktop I ever purchased and so a couple of years ago I bought one on eBay as a memento.
posted by AGameOfMoans at 1:32 PM on September 17, 2015 [1 favorite]

Growing up we had a ti-99/4a. No PEEK or POKE, so that was all just a mystery to me. I spent a lot of time typing programs into that damn thing in basic and extended basic though.
posted by fimbulvetr at 1:34 PM on September 17, 2015 [1 favorite]

At school our PET's were pretty much obsolete by the time I got there, and were finally done in when someone figured out you could open the case. Most of them got opened and destroyed by damaging the electronics and occasionally spilling stuff from the comestibles that got stored in them.

Does anyone remember the olden days, when there were computer magazines that had programs you could key into BASIC?

I used to key in programs from ANALOG into my Atari 600XL. As I had no tape or floppy drive I couldn't store anything I did on it. That meant I'd spend all day studiously typing in a program, then debugging the results (SO happy when they added per-line checksums), playing with the resulting program for a couple of hours, then turning it off. If I liked a game and wanted to play it again, I had to type it in again. Occasionally I'd spend all day typing in a particularly cool sounding game only to find at the end that I couldn't run it because I'd have used all 16k of ram.
posted by Poldo at 1:34 PM on September 17, 2015 [2 favorites]

The C64 had a legendarily slow BASIC interpreter, written by Microsoft natch, that did ridiculous things like convert integer variables into floating point to do math on them, then convert back for storage, because they couldn't fit more than one set of math routines in its 8K of ROM (or at least, that's the charatable explanation).
posted by JHarris at 1:37 PM on September 17, 2015 [2 favorites]

Beagle Brothers-Peeks, Pokes and Pointers for the Apple II Ahhh, junior high computer lab memories.
posted by jeribus at 1:42 PM on September 17, 2015 [8 favorites]

My fire department had a salesman demo the PET. Among the things he showed us was how the two floppy disk drives could transfer data between them without being connected to the PET (IEEE-488?).

We didn't buy it, we bought a DEC Rainbow instead.
posted by tommasz at 1:46 PM on September 17, 2015 [1 favorite]

There were several POKEs to memory in that region that produced interesting effects. Another was POKE 59468,0 which reset the machine. Once upon a time I had them all memorized but those neurons lost their signal many years ago.
posted by scalefree at 1:51 PM on September 17, 2015

And of course I once set it up to print some stupid damn thing on an endless GOTO loop and walked away. We all did.

If there isn't a new wave revival band called 20 GOTO 10, there should be.
posted by brianrobot at 1:55 PM on September 17, 2015 [11 favorites]

And of course I once set it up to print some stupid damn thing on an endless GOTO loop and walked away. We all did.

My first summer job was an internship at NASA. I got to write a FORTRAN program that would run on their CRAY XMP-4. I got some flack for the amount of computing time I was using ("Do you know how much money that time is worth?"), but it was good-natured and it didn't bother me.

No, the only time I got embarrassed was when I discovered that the command I was using to delete all the various extra versions of my files (name;1, name;2, etc.) and had been using a *lot* was actually printing them out at a central printer before deleting them. I snuck over there and stealthily made my way out with truly vast quantities of used printer paper.
posted by Four Ds at 2:13 PM on September 17, 2015 [5 favorites]

Apparently these days you need to compile the kernel with a special option to be able to do PEEK/POKE on Linux. :(
posted by save alive nothing that breatheth at 2:14 PM on September 17, 2015 [1 favorite]

Growing up we had a ti-99/4a. No PEEK or POKE, so that was all just a mystery to me. I spent a lot of time typing programs into that damn thing in basic and extended basic though.

I think there was actually a CALL syntax, like the CALL HCHAR/VCHAR/SOUND invocations, but for memory... yeah, it looks like not only was there CALL PEEK/LOAD for Extended Basic (which I never had, sigh), if you had the right memory expansion (which I also never had, sigh), you could hit video memory with CALL PEEKV and CALL POKEV.
posted by weston at 2:36 PM on September 17, 2015 [1 favorite]

Forgive me for pasting an old comment here:

My Commodore 64 was connected to our only TV in the living room of our apartment. It was 1984 and I was in the 7th grade. Endless begging had got me the computer for my birthday, but there was no money in the budget for a tape drive, much less the ridiculous luxury of a floppy disc drive. It was impossible to explain to my parents why it was vital that I have some sort of storage medium for my programs.

I was in the middle of typing in a game (I think it was like Snake) from Compute! magazine. By "in the middle" I mean that I had been very slowly and carefully typing in endless strings of digits hunched over the machine on the floor all day and had at least another full day of typing left before I could enjoy the sweet success of playing my game on my computer that I typed in myself. When we went fishing, my father would tell me that I had no patience. He had no idea how patient I could be. I was focused like a laser.

The only outlet available to plug in my C64 was a switched outlet intended probably for a table lamp. I had put tape all over the switch to hold it in place and made a sign in bold red letters admonishing everyone: "DO NOT TURN OFF THIS SWITCH!!!" Of course, my Mom came home one day and said, "Why is all of this tape on this switch?", and casually turned it off. She had a long track record of doing the worst possible thing in any given situation. I was sent to my room for the rest of the day for saying the "F word".

The next day, I started making my own tape drive from my old cassette recorder, a breadboard that I stole from my brother, some components from Radio Shack and a design that I got from a magazine.

Never again, I swore. Never again.
posted by double block and bleed at 2:38 PM on September 17, 2015 [24 favorites]

I'll look this thread up the next time I want to buy a PEEK in a POKE.
posted by Pope Guilty at 2:40 PM on September 17, 2015 [1 favorite]

We had a FORTH cartridge for the Ti-99/4a, so no PEEK/POKE, just blocks and DATA and CODE. We spent most of our time trying to get the speech synth to make fart noises, as I recall.
posted by bonehead at 2:45 PM on September 17, 2015 [4 favorites]

OMG FORTH! Wow. My ambitions were Extended Basic and the Assembler, I can see they were too small. That would have changed my whole world.
posted by weston at 3:00 PM on September 17, 2015 [1 favorite]

The C64 had a legendarily slow BASIC interpreter

I wasn't often jealous of the BBC Micro kids -- C64 games were better! -- but oh my God, I was so envious of BBC Basic's inline assembler.
posted by We had a deal, Kyle at 3:15 PM on September 17, 2015 [2 favorites]

When I left $childhood-home I had no place to store $stuff (this is a thing us working class folk had to negotiate, I promise) and so I dumped my fully loaded TRS-80 Model I along with all the system disks, cassettes, and my own software into a garbage tip.

Oh, my Color Computer went in there, too.

Full sets of manuals for everything. NewDOS/80. The works.

I still regret it, but what what choice did I have? Nobody wanted this stuff back then, and nobody thought it worthy of storage.

I guess I made the existing hardware into collectibles?
posted by clvrmnky at 3:41 PM on September 17, 2015

The reason all these programs used POKE and DATA commands was because the BASIC interpreter (on the C64 at least) was painfully slow for running a program directly from BASIC. Programs POKEd directly into machine code ran in a flash.

The other reason was that you couldn't do anything interesting otherwise.

When I was a kid in the 80s, I had a subscription to 3-2-1 Contact magazine. At the back of each issue would be a little BASIC program that was meant to be cross-platform (C64, Apple II, IBM). But because of the cross-platform requirement, they were all text-only things like Lemonade Stand or tiny little choose-your-own-adventure stories and such.

Even then, there were always special instructions to substitute certain lines for certain computers, because something as basic as clearing the screen was platform-specific -- HOME or CLS or the user-friendly C64 version PRINT CHR$(147)...
posted by neckro23 at 3:50 PM on September 17, 2015 [4 favorites]

What blew me away about the extended BASIC firmware cartridge on the TI-99/4a were its sprite calls. I was able to make my own iterations of Lunar Lander and Frogger. 16k was just enough to do some interesting things. I don't recall anything else on the market that let a kid mimic the game play of "real" video games as well. Even more amazing was controlling sprites with a joystick and coming close to what conventions a mouse would use without having seen Engelbart's demo.
posted by lazycomputerkids at 3:52 PM on September 17, 2015 [3 favorites]

I programmed in FORTH in grad school in 2002. Hah, I didn't know it had a history outside labs. My professor strongly felt programming a microprocessor in Forth was the best training one could get to understand memory and computing etc without doing Assembly. I remember bring the only one who actually liked it and when I was the TA the next semester had to take a lot of grumbling from the undergrads that they had to work on an ancient machine.

Good times :-)
posted by viramamunivar at 3:56 PM on September 17, 2015 [1 favorite]

I've heard this too, but never a confirmed "yes, doing this too long *permanently* damages the monitor and I've seen it" unless bonehead's confession above is such a thing. Ditto for the fabled HCF (Halt and Catch Fire) instruction.
posted by RobotVoodooPower at 4:05 PM on September 17, 2015 [2 favorites]

omg tecg I'm dying here
CHESS CHAMPION MKI MACHT KEINE FEHLER!
posted by yoHighness at 4:17 PM on September 17, 2015 [1 favorite]

Killing it this month, JHarris!
posted by comealongpole at 4:23 PM on September 17, 2015 [4 favorites]

"I've heard this too, but never a confirmed "yes, doing this too long *permanently* damages the monitor and I've seen it"

I made pocket money in high school by repairing PETs broken by the 'killer poke'. The exact details are lost to time & faulty memory, but I think it was simply a matter of fault-finding around the horizontal flyback circuit in the monitor (a TIP55A/58A drive transistor?).

I bought my first bottle of ouzo with money made from those repairs, which may help explain the faulty memory…
posted by Pinback at 4:28 PM on September 17, 2015 [6 favorites]

Heh. A sort of wetware POKE of its own, apparently.
posted by weston at 4:41 PM on September 17, 2015 [5 favorites]

Later versions of the machine changed the hardware in such a way that, if the user used this command, it would cause the monitor to lose sync and word is, if left too long, could damage it.

I'm too young to remember the C64 (we had one, but it kept breaking and I only ever used it to play Frogger anyway) but I do remember the bad old days of hand editing XFree86 config files while worrying that I might accidentally destroy my monitor.

Also, in the late 1990s wasn't there also a virus (or an urban legend of a virus) that would break your CRT by rapidly changing the scanrate?
posted by RonButNotStupid at 4:48 PM on September 17, 2015 [2 favorites]

pfff this is nothing, I saw a guy perform dim mak on a VIC-20

you wouldn't know him, he goes to a different school
posted by prize bull octorok at 4:50 PM on September 17, 2015 [7 favorites]

I remember hearing a story back in the day that there was a DEC system with a killer key. A room full of terminals connected to the DEC machine with a person at almost every one typing away. You walk in. Casually pause near an unused terminal. Lean over with finger on the TAB key. Hold it down for a few seconds. Watch everyone jump and yell when all the terminals in the room shut down as the whole computer crashes. Run like hell.
posted by njohnson23 at 5:12 PM on September 17, 2015 [1 favorite]

I knew a guy who almost destroyed a VAX-11 through sex, and I once crashed that same VAX using assembly language and the fact you could directly address where the next instruction was in memory (and then defining that as a nonexistent location), but I'd never have screwed with my Apple ][+ that way.
posted by mephron at 6:07 PM on September 17, 2015

>>which led to some acrid smoke, which led to "Kirking" a machine becoming a catchphrase synonymous with electric death.

>Do not let this guy near a starship!

Always wondered how he was able to reprogram the Kobayashi Maru simulation.
posted by radwolf76 at 6:42 PM on September 17, 2015

JHarris, if you ever did a megapost about the TI 99/4A, I'd read the whole thing.
posted by SpacemanStix at 8:38 PM on September 17, 2015

Pretty sure the ti99/4a had PEEK (CALL PEEK(), probably) but definitely did not have POKE, and PEEK without POKE is fairly useless. The extended BASIC cart was nice, esp. the sprites, and the addition of AND and OR to the IF statements, missing in the onboard ROM BASIC (though you could emulate them with * and +) If you're into ti99/4a stuff, be sure to take a look at the parsec page.
posted by smcameron at 9:00 PM on September 17, 2015

Did they give away those PET computers to elementary schools for free? Because California schools were already broke in the early 80s when I was there, but we had 'em too.

I identify watching boys nerding around on those PET machines as a first moment I became aware of gendered behavior differences. I was a committed tomboy and generally mistaken for one of the boy-children I played football with, but I didn't understand any of the programing stuff you guys are talking about above, and didn't even really feel like playing Oregon Trail. I do remember finding those tape drives kind of satisfying to open and close.

Even though it's a little uncomfortably gendered, it's cool reading folks' reminiscences here. I sometimes feel sad that my childhood happened after the golden age of tinkering, but this makes me realize that my generation was tinkering in a different way. Although, duh, I guess we invented Apple and Microsoft etc so...
posted by latkes at 9:43 PM on September 17, 2015 [1 favorite]

The joys of unprotected memory! Back in the early 2000s I was programming in LabView/CVI - a C-like environment. I'd written a program to do some stuff, and then it wrote the results to a file. After the program ran, I tried to read the file in a text editor and it was just unreadable characters. Hmm though I, best open this in a hex editor to see what's going on and:

BA AD F0 0D
BA AD F0 0D
BA AD F0 0D
BA AD F0 0D
...

It was a completely surreal moment of 'holy fuck the computer is talking to me' and 'oh shit what have I broken'.

Turns out the LabView people were just a whole lot smarter than me and it recognised when it was being fed unallocated memory (I eventually tracked it down to a screwed up malloc call).
posted by KirkpatrickMac at 11:12 PM on September 17, 2015 [4 favorites]

I've said it before I think, but my C64 was the last computer I owned that I really understood on a deep level. I knew exactly how that machine - right down to the processor level - worked.
Now, with multiple layers of OS and BIOS and caches and drivers and a bunch of stuff this hardware geek doesn't understand, computers are just magic boxes again.
posted by rocket88 at 7:53 AM on September 18, 2015 [4 favorites]

"BAADF00D" is my favorite hexadecimal value, BTW. Much funnier than "DEADBEEF" or such.
posted by JHarris at 8:08 AM on September 18, 2015 [1 favorite]

Agreed entirely rocket88. I think that's part of the appeal of things like Arduino and (to a lesser extent) Raspberry Pi though, to be machines where the programmer is much closer to the metal. They also feel more "honest" than the big operating systems, which have gotten so complex that it doesn't seem implausible at all that the system software itself could be conspiring against the user, in the name of rights holders or the NSA.
posted by JHarris at 8:11 AM on September 18, 2015 [3 favorites]

I knew a guy who almost destroyed a VAX-11 through sex

...Back the bus up a moment.
posted by delfin at 8:12 AM on September 18, 2015 [1 favorite]

Back the bus up a moment.

I assumed backing up to the bus was what almost destroyed the VAX.
posted by bondcliff at 8:20 AM on September 18, 2015 [1 favorite]

If this has anything to do with mounting a scratch monkey, I'm outta here.
posted by delfin at 8:21 AM on September 18, 2015 [1 favorite]

My address is a killing poke.
posted by rum-soaked space hobo at 9:09 AM on September 18, 2015 [1 favorite]

(Please pardon more fuel on the above magazine program typing sorta-derail, but the Internet Archive has what looks like the full run of Compute! up as downloadable PDFs. May I suggest starting with the first issue I ever bought? Remember: I'm old!)
posted by mintcake! at 9:20 AM on September 18, 2015 [1 favorite]

Tell me of your homepage, Usul.
posted by rum-soaked space hobo at 12:32 PM on September 18, 2015 [2 favorites]

brianrobot: If there isn't a new wave revival band called 20 GOTO 10, there should be.

That's the name of my Pet Shop Boys cover band.

... my Commodores cover band.

... my Apples in Stereo cover band.
posted by hanov3r at 1:23 PM on September 18, 2015 [5 favorites]