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April 1, 1972: Write Only Memory 233

Embedded Geek writes "While digging around Jack Ganssle's site, I came across an amusing prank from days gone by. In 1972 Signetics recognized April Fools day by printing a full color datasheet (scanned sheet 1 and sheet 2 here) for a Write-Only Memory (which accepts data but never reads it back), a considerable effort when documents were made via literal "cut and paste". Packed with jokes both obvious (a graph of "number of pins left versus number of insertions") and subtle ("Vdd = 0V +/- 2%") it's worth a chuckle."
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April 1, 1972: Write Only Memory

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  • by geoffsmith ( 161376 ) on Friday May 31, 2002 @04:57AM (#3615899) Homepage
    Writing perl code! Write once, read never.

    Websurfing done right! StumbleUpon []
  • shhhs... (Score:2, Funny)

    by DanThe1Man ( 46872 )
    I thought I just had to avoid reading slashdot one day a year to avoid April Fools crap.
    • Re:shhhs... (Score:2, Funny)

      by gazbo ( 517111 )
      Aye. But don't worry, It's one of the most linked to April Fools, and from the seventies, so there is no chance that we haven't heard of it before.
  • I bet there's some cypto/privacy types out there who think this is still a good idea
  • Holy cow (Score:2, Funny)

    by ObviousGuy ( 578567 )
    You people ARE nerds! Jebus. I thought everyone was just faking it!
    • Re:Holy cow (Score:1, Funny)

      by Anonymous Coward
      Nice, quoting from Simpsons? And you are not a dork either? Quoth from the Comic Book Guy: "You laugh at me, oh that is rich!"
  • more about their fabrication process. Their "unique SEX process" intriques me...
    • Did you see the "SEX[7]" note at the bottom of page 1? it says "[7] You have a dirty mind..."

      If I recall correctly, both Signetics and National Semiconductor managed to sneak a few bogus datasheets into their released databooks from time to time. I first saw of this particular one a couple three years ago; I think someone posted a link to it on or a similar newsgroup.
  • by ( 463190 ) on Friday May 31, 2002 @05:03AM (#3615910) Homepage
    I get a lot of spam, so I've been working on a hardware accelleration card for /dev/null. This'll save me having to develop my own design in an expensive FPGA.
    • by phil reed ( 626 ) on Friday May 31, 2002 @08:04AM (#3616279) Homepage
      I get a lot of spam, so I've been working on a hardware accelleration card for /dev/null.

      Many years ago, I used to go to DEC Users Group meetings. In the evenings, we'd have "sessions" where the operating system developers would come around and tell war stories. I remember one time that one of the RSX-11 (one of the PDP-11 operating systems) developers was telling us that writes to the Null device (NUL:) was found to be considerable slower than writes to real hardware. Therefore, they had begun development of a null hardware device to be plugged into the system. It was to be called the NUL-11 board, and they had developed quite a bit of specification material for it, unfortunately lost (this was in the early '80s). Very fun stuff.

  • by Brynath ( 522699 ) <> on Friday May 31, 2002 @05:04AM (#3615912)
    Something they can sell that has Perfect Copy Protection!
  • by JaredOfEuropa ( 526365 ) on Friday May 31, 2002 @05:04AM (#3615913) Journal
    There are circuits in use that are essentially a write-only memory like this (but without the need for a 6 foot fan!), combined with a comparator and possibly a one-way encrypter. You can store an encrypted password in there, which then can never be read back in its encrypted form. Plaintext phrases can be encrypted and compared against the stored password.

    One existing application is on debit cards (cards that are charged with a cash amount on the card itself).
    • > Plaintext phrases can be encrypted and compared against the stored password.

      Explain again how you read from this write-only memory then?

    • but you are wrong.... cash cards/chips CAN be read. you have to know how much is left on it. and a password storage as you say ALSO can be read as you have to have an indication if the match was positive.

      so in fact if you get ANYTHING out of a device it does in fact have a read capability.
    • FYI, This data sheet made it into the Signetics IC handbook, which is where I first saw it back in my PDP 11/35 days. I liked the Drain pin. It was properly placed over the Bit Bucket to prevent spilling data.
  • by Raedwald ( 567500 ) on Friday May 31, 2002 @05:05AM (#3615914)

    This has been in The Jargon Lexicon [] for ages. Don't all slashdotters know of it?

    • Byte Magazine also featured a Write Only Memory in one of their April issues. A wooden block with wires attached :-))
    • by tswinzig ( 210999 ) on Friday May 31, 2002 @09:57AM (#3616776) Journal
      This has been in The Jargon Lexicon [] for ages. Don't all slashdotters know of it?

      I must have missed the part on this site where it says, "YOU MUST READ THE ENTIRE JARGON LEXICON BEFORE READING SLASHDOT."
      • Shocking oversight. Here, I'll fix it:

        You must read the ENTIRE jargon lexicon before reading Slashdot

      • I must have missed the part on this site where it says, "YOU MUST READ THE ENTIRE JARGON LEXICON BEFORE READING SLASHDOT."

        Actually, since the published versions of the Jargon file are called the Hacker's Dictionary (the latest being the New Hacker's Dictionary), a dictionary is a compendium of language common to a group, and the Slashdot readership are hackers, for the given definition of hacker in the dictionary, then the Dictionary *is* required reading - or at least reference.

        Sort of like how knowing english for or knowing japanese for are requirements.

        Evan (Don't take this post too seriously - I'm justifying for justifications sake)

      • I must have missed the part on this site where it says, "YOU MUST READ THE ENTIRE JARGON LEXICON BEFORE READING SLASHDOT."

        Even if us lowly posters haven't (although you should), it would be nice if our nerd-overlord editors who put the story on the front page have given the jargon file a quick skim.

        "Breaking news on Slashdot! Some programmers use funny words like 'foo' and 'bar' in their code, instead of *real* variable names!"

  • I stronly suspect the main site is going to die, so here's a mirror on my website:

    Pic 1 [] Pic 2 []
  • by vidnet ( 580068 ) on Friday May 31, 2002 @05:05AM (#3615918) Homepage
    You mean like the windows registry?

    Crap goes in, but doesn't seem to go out until you have to reinstall a month later :)
    • > You mean like the windows registry?
      > Crap goes in, but doesn't seem to go out until you have to reinstall a month later :)

      Or the abuse department at any Chinese ISP, the difference being that crap comes out.

  • 'Read protection' (Score:4, Informative)

    by Ed Avis ( 5917 ) <> on Friday May 31, 2002 @05:06AM (#3615922) Homepage
    On the BBC Micro you could add 16Kbyte banks of 'sideways RAM'. I remember that some upgrades had a 'read protect' switch, which sounded very odd. I think it was for compatibility; read protect made the upgrade effectively invisible.
    • The Commodore 64 has something similar. It had 64k, but not all of it was readable because of the ROM chips. You could write data there, but when you tried to read you'd only get the ROM data. You could disable the ROM's and read the data you put there before.

      Nifty idea when memory was so limited!
      • Re:'Read protection' (Score:2, Interesting)

        by BdosError ( 261714 )
        And that led to a bunch of weird (to the uninitiated) code like:
        for i=49152 to 51200: poke i, peek(i):next i

        But if you wanted to turn of the ROMs to use the underlying stuff in RAM, this is what you had to do, if you wanted access to some of that ROMs code. Weird, but interesting.

        Ah the creativity of limited resources.
      • It's not because of limited memory but limited address space. The switching between ROMs and RAM needs to happen because there is more than 64Kbyte of total (ROM+RAM) memory in the system, but the 6502 processor has only 16-bit addressing. If memory had been a bit more limited, there wouldn't have been any need for these tricks :-P.
    • "read protect made the upgrade effectively invisible."

      I know I love buying new hardware, sticking it in my machine, and never hearing from it again.
  • by rhysweatherley ( 193588 ) on Friday May 31, 2002 @05:07AM (#3615923)
    It took Intel 30 years to acheive a chip that has the same cooling requirements:
    The 25120 is easily cooled by employment of a six-foot fan, 1/2" from the package. If the device fails, you have exceeded the ratings. In such cases, more air is recommended.
    Signetics were way ahead of their time.
  • Mirror (Score:1, Redundant)

    In case the site is slashdotted, you can get the images from there [] and there [].
  • Form this [] sheet: "...the 25120 will obtain 50% higher speed than you will obtain..."the 25120 is easily cooled by a six foot fan, 1/2" from the package..."

    So, they had overclockers back in 1972? Nothing new under the sun, I guess...

  • therefor, the message content is: void.
  • ... 30 years too late for this?
  • Huh? (Score:3, Funny)

    by jnievele ( 469461 ) <> on Friday May 31, 2002 @05:19AM (#3615955) Homepage
    I didn't know that DAT backup tapes were invented in 1972... ;-)
  • As far as the computer and it's memory hierarchy is concerned, there IS write only memory. The printer, for example, in the absence of a scanner, is just this, as could be certain video displays.
  • by pawlie ( 23653 ) on Friday May 31, 2002 @05:25AM (#3615972)
    Brilliant: slip-on latex protectors for preventage of VD!! (Voltage Destruction) Pill packaged devices do not require protection!
  • by octalman ( 169480 ) on Friday May 31, 2002 @05:27AM (#3615976)
    My favorite feature of this device is that typical bit capacity is 35% to 75% of "guaranteed" bit capacity.
  • by MadFarmAnimalz ( 460972 ) on Friday May 31, 2002 @05:28AM (#3615979) Homepage
    I'd rather thought that /dev/null was the most elegant WOM out there...

    Heck, they even coded it such that it has infinite capacity, or a very high capacity in any case.

    Could someone dedicate a machine for a few years with a shell script running an infinite loop writing data to /dev/null? I personally think it's about time we found out how much you can stash in there.

    • I personally think it's about time we found out how much you can stash in there.

      Do you think /dev/null is a /dev of holding? Will the data all disappear when it reaches capacity?

      Speaking of 'of holding', one of the funniest references I recall was on the Twin Peaks mailing list way back when. Someone pointed out that a Laura said she kept some casette tapes in her bedpost, but that her bedpost was too small. The author suggested that she must have 'a bedpost of holding'.

    • Make dev/null an append only file someday and just see all the wonderful information being collected.

      There really is a ton of stuff. Append only to prevent that cronjob from wiping it out when it only has > instead of >>.
      • Ever have /dev/null deleted by accident? Interesting things happen, and it's not easy to track down.
        • Ever have /dev/null deleted by accident? Interesting things happen, and it's not easy to track down.

          Actually, yes. While running an ISP back in 1996, I had a support tech who managed to overwrite /dev/null on a UnixWare box without root access.

          All I can say is thank God he realized he did it. I can't even begin to guess how long it would have taken me to find it.

          We never did figure out how he managed to do that and could not duplicate the problem after we fixed it. I think we gave him a raise.

          The incident even inspired us to start a contest for our support techs. We offered a cash prize to the first one who could root our shell server. The only restriction was that they weren't allowed to access console or sniff packets. Sadly, no one collected the prize, although one managed a nearly perfect forgery of an email from root (an actual email from root was their goal.)
          • An ex-coworker of mine deleted the parent directory while in a subdirectory of said-parent. (under a version of SCO).

            System stayed running for about 5 seconds and then crashed hard. couldn't duplicate the problem.
    • I'm flabbergasted that the parent is at +4 _insightful_ as I type this... C'mon people, an infinite loop writing to /dev/null to see how much you can cram in there?

      :-) Oh well, it's your party :-)

  • by robolemon ( 575275 ) <nertzy@gm a i l . c om> on Friday May 31, 2002 @05:31AM (#3615992) Homepage
    After writing up the paper and printing it in color (back in the day before cheap color printing), the Signetics engineers retire to the local bar.

    After laughing it up for a bit, their boss walks in. He is visibly angry.

    Boss: "Miller! Wilson! Did you waste our money again? I found the Write-Only Memory specs! That's it! The six-foot fan was one thing, but now you guys have crossed the line. How are you going to explain yourselves?"

    Miller: (angrily to Wilson) "I thought you said he wouldn't be able to read it!"

    Slashdot Readers: (groan)

    • Special features

      Because of the employment of the signetics' proprietary Sanderson-Rabbet Channel the 25120 will provide 50% higher speed than you will obtain.

    Err .. mmmkay ??!?!?

  • by Bazman ( 4849 ) on Friday May 31, 2002 @06:29AM (#3616083) Journal
    "640k of Write-Only Memory ought to be enough for anybody".

  • I remember a datasheet from Phillips on the DED.(Dark Emitting Diode) and a Texas instruments publication on a spec for the FUDGE gate.

    It isnt new, but that one is obviousally old enough to possibly be the first....
  • by Pogue Mahone ( 265053 ) on Friday May 31, 2002 @06:36AM (#3616097) Homepage
    I remember this one when it first appeared. Does that make me "venerable"?

    On a similar line, somewhere at home I have a spoof datasheet from Nominal Semidestructors giving information about the new Polish Operational Amplifier.

    What I'm missing, however, is my copy of the table of variation of pi with temperature and pressure, which I believe was given to all engineering freshmen at Cambridge at one time. If anyone can help me to locate a new copy I'd be grateful. Please reply here or email me (see homepage).

  • Footnote 6... (Score:4, Informative)

    by markmoss ( 301064 ) on Friday May 31, 2002 @07:31AM (#3616197)
    They even planned far ahead. In 1972, "VFF = 6.3VAC" was obvious in itself, but for you youngsters that don't know about vacuum tubes they added the footnote "6. For the filament heater, of course."

    Yes, it's now a very old joke, but it's been fun watching a new "generation" rediscover it every five years or so.
  • If this technology could be incorporated into a CD or DVD, all of their "piracy" concerns go away.

    Sure, there are some pesky customer satisfaction issues, but let's keep our priorities straight. OK?
  • I had used this very chip as an example of the problems of searching with Google in a prevous /. post - I was trying to find electronic forms of the datasheet, and was using it as an example of why I felt Google needed boolean searches.

    The really funny thing is, that while this created a bit of a message thread on /., I can find that thread with neither /.'s built-in search nor with Google.

    Making fake releases is a tradition many organizations (and /. ;>) follow - go read QST [http], for example. Why, I even heard Microsoft is getting into the act - they released a fake news release about focusing on security and reviewing their code, but I think they jumped the gun by a couple of months....
  • Yeah, my hand-writing is write-only, or so everyone tells me...
  • I protest, this chip is obviously not JEDEC [] compliant and is therefore prone to silent failure. RMS and EFF ought to kick their asses.
  • In case anyone cares (Score:3, Informative)

    by overshoot ( 39700 ) on Friday May 31, 2002 @09:05AM (#3616496)
    Friends who work at Philips (which bought Signetics years ago) tell me that the 25120 datasheet may be updated and reissued. Keep an eye out for it once Philips [] gets a usable website.
  • The data sheet for the 1Z2Z vacuum tube (circa 1966) contained items like a "urinated tungsten filament" and a monode structure (one less than diode), IIRC.

    If humor exists prior to the Google...can anyone laugh?
  • Man discovers fire.
  • by rnturn ( 11092 ) on Friday May 31, 2002 @09:47AM (#3616705)

    I know people who have copies of that data sheet.

    Another one that was good for a laugh was the ``Damn Fast Op-Amp'' that appeared in a normal device catalog from one of the major electronics device manufacturers (like Signetics, Fairchild, National, or maybe even AMD -- I'm leaning toward the latter but I can't remember any more. Darned cobwebs.) I used to enjoy asking interns to look up some information for me in the catalog and wait to see if they noticed it. You could tell if they did from the laughter.

    Another one from the same time frame (1980-ish) was the announcement -- on official IBM product sheets -- of a Galactic Edition' of the VM/CP (or was it VM/CMS?) operating system. This included advanced features like the one that allowed users to create and destroy their own planetary systems and such.

    Oh those were the days. Bet you don't see stuff like this appearing in official company literature any more. Hell, there'd probably be someone suing the company after they'd been traumatized upon seeing such offensive material (like `damn') or claiming fraud when their personal solar system didn't appear.

    • Another one that was good for a laugh was the ``Damn Fast Op-Amp'' that appeared in a normal device catalog...
      That actually was not a joke. Those op-amp were damn fast. Seriously. They were an extension to the line of fast op-amps from (I believe) National Semiconductor.

    • Geez, I hate to reply to my own post but here's a link to a page with the text of the fictional IBM operating system -> []. The product was an improvement over the virtual machine concept in which one could now have a virtual universe. You'll have to read it to appreciate it (or not).


  • Back in the days before memory came on SIMMs, a few shady PC hardware manufacturers included "write-only memory" on their motherboards. These devices made the system look like there was an impressive amount of memory on the motherboard, but in actuality they were just molded plastic with unconnected IC pins, filling the spots one would put real RAM chips.
  • Back when WORM drives were all the rage, some engineers at Atari actually implemented a worn: (Write Once, Read Never) device in Atari BASIC. I don't remember how it was done (it's buried in an old issue of Compute! that I probably threw out years ago) but I actually got to try it out on a computer at the school I was going to (back in the day when everyone had Apple ][s, this school was using Atari 800s).

    It was just an Easter Egg; I suppose some Unix geek at Atari just decided it needed its own equivalent of /dev/null.

  • press release (Score:3, Informative)

    by trb ( 8509 ) on Friday May 31, 2002 @10:31AM (#3617000)
    There was an amusing press release [] that accompanied the Signetics WOM.
  • I thought write-only memory was Microsoft's solution to the problem of memory protection in Windows.

    You know, misbehaving applications accidentally used to scribble on other apps' memory spaces. When Microsoft forced the PC industry to install banks of WOM, suddenly every crash became an application error--those applications were not conforming to the Windows API. Instead of scribbling on another application's memory, the app should have been scribbling to the WOM.

    It was brilliant because overnight Microsoft foisted millions of dollars in OS support expenses on to application vendors.

  • ...partcularly in hardware encryption (Debit cards, PVRs, Access control systems, whatever. The point is that a chip has basicly two functions: SetKey(key) and Decode/Encode(data). You set the key, but you can never read the key. Of course the chip will use the key internally to come from plaintext to chipertext or vice versa, but as long as the encryption is strong it doesn't matter. (Def. of strong: Having plain & ciphertext doesn't help to find the key, most algorithms today are strong, the zip encryption is weak though).

    Of course this means you need a specialized chip, and not a general CPU, which is overkill in many cases..

  • From what I remember, there actually was a form of write-only memory at one point. Some of the sound registers on the Commodore 64 were "write only" in the sense that you could poke any value (well, from 0-255) into the memory location and it would change the nature of the sounds generated. However, if you tried to peek into the address, it returned with zero no matter what. Can anyone verify this? It's been a good bunch of years since I've had one of those to program.

    Not truly write-only memory (in the sense that you could get a value, albeit a painfully useless one), but it seems to come close to the spirit.

  • This was a pants-wetter back in 1972. Though I remember some different tearsheets -- they had marketing material as well, I think. One showed a "modified TO-5 case" that was in fact a photo of a water tower. The WOM campaign became a bit of cult humor for a generation of engineers and hobbyists.
  • I enjoyed it muchly back in the '80s when I first saw it, and now I will have a computer version...much better than the photcopied version that was many generations old...

  • My old man was an eletrical engineer at Control Data for many years. He brought home doezens of things like this. I remember specifcations for the Write-Only Memory. I remember the FED (Flame-Emitting Diode; a cover photo from EDN magazine), the NED (Noise-Emitting Diode), alternative logic gates like the "DON'T" gate (no matter what two bits are input, the output is zero). I remeber even linear components like the IN-OP AMP. I loved this stuff. My dad was also a radio amateur and he and friend wrote an article proposing solving the spectrum shortage by using the negative freqeuncy spectrum. They included diagrams showing you how to bury your antenna and stick the ground rod up in the air.

    Who says engineers aren't funny (at least to each other)?

  • This reminds me of a friend of mine who had a DAT drive for his Mac. He would do weekly backups of his entire (500meg or so) hard drive on this same tape. He was basically rewriting over the same stuff all the time. Apparently these tapes (I don't know anything about tape drive storage) degrade after repeated writings. So one day his system is hosed and he goes to the tape to recover. Nothing will read.

    He called me on the phone to discuss the situation. As we concluded our conversation, I remember him sort of defending the reputation of the device by saying in a very sincere voice, "It works great for backups, it just doesn't work too well for restoration." And he was serious.

"To take a significant step forward, you must make a series of finite improvements." -- Donald J. Atwood, General Motors