4 ms·

IDK. The wikipedia article on the 1403 does not mention any 1403A, just 1403N and 1 through 7. I doubt the overprinting was an accident, 'PUT SKIP (0);' worke

IDK. The wikipedia article on the 1403 does not mention any 1403A, just 1403N and 1 through 7. I doubt the overprinting was an accident, 'PUT SKIP (0);' worked for all the versions of PL/1 I used from 1970 through around 1990. Didn't even IBM use it for drawing maps and graphs on the 1403? I remember that the standard was to fill a region with O's to get a lightly shaded region, next darker was O overstruck with X, then O overstruck with V and A, and darkest of all, X + O + V + A all on the same print position. The great story I heard about these printers but never verified is that there were 132 separate hammers, one for each print position 1-132. Thus, as the print chain spun around, each hammer fired when the correct character was in position for that hammer, and if you printed a line that matched the sequence of the characters on the chain, all the hammers would bang simultaneously, breaking the chain. Whether or not the sequence of the characters on the chain was a secret, IDK.

kens 8y ago
I've heard the breaking chain story many times, but I suspect it's mostly an urban legend. At least on the 1403, the hammers can't all fire at once. The chain and hammers have different spacings so only one hammer is lined up at a time, 11.1μs apart; the worst you could do is fire every third hammer in rapid sequence. For reference, a standard chain sequence is 1234567890#@/STUVWXYZ‡,%JKLMNOPQR-$*ABCDEFGHI+.¤ The 1403's print chain is pretty complicated to understand, so I built an animation: http://righto.com/ibm1401/printchain.html http://righto.com/ibm1401/printchain.html
- abraae 8y ago
  I used to work at IBM as a CSR (maybe we were CEs back then?) fixing 1403s and other mainframe boxes. Man it would have been so useful to have your fantastic animation back then. I came on the scene too late to ever get any formal training on 1403, so I ended up learning most of it the hard way. I don't think I ever fully understood the hammer mechanics as you have explained it. An animation is truely worth 1000 words.

kens 8y ago

I've heard the breaking chain story many times, but I suspect it's mostly an urban legend. At least on the 1403, the hammers can't all fire at once. The chain and hammers have different spacings so only one hammer is lined up at a time, 11.1μs apart; the worst you could do is fire every third hammer in rapid sequence. For reference, a standard chain sequence is 1234567890#@/STUVWXYZ‡,%JKLMNOPQR-$*ABCDEFGHI+.¤ The 1403's print chain is pretty complicated to understand, so I built an animation: http://righto.com/ibm1401/printchain.html http://righto.com/ibm1401/printchain.html

abraae 8y ago
I used to work at IBM as a CSR (maybe we were CEs back then?) fixing 1403s and other mainframe boxes. Man it would have been so useful to have your fantastic animation back then. I came on the scene too late to ever get any formal training on 1403, so I ended up learning most of it the hard way. I don't think I ever fully understood the hammer mechanics as you have explained it. An animation is truely worth 1000 words.