The Perfect Computer - 36 bits?
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From: John L on 7 Mar 2007 17:44 >One could also claim that the standardisation of twos complement for >integers and signed magnitude for floating-point was settled at the >same time and for the same reasons. Twos complement, sure. Floating point, heck no. Other than the S/360 clones, the only maker I can recall using the IBM floating point format was Data General. Two's complement has nice numeric and implementation properties. But IBM's S/360 floating point was botched, and the hurried retrofit of guard digits only helped a little. Between the hex normalization and the lack of rounding, they lost at least a full digit compared to obvious alternatives. It wasn't until the IEEE format came along that the floating point format issue was settled. R's, John
From: Charlie Gibbs on 7 Mar 2007 17:54 In article <esnbn5$i38$1(a)gemini.csx.cam.ac.uk>, nmm1(a)cus.cam.ac.uk (Nick Maclaren) writes: > And, to clarify, IBM's dominance of the IT industry in the 1960s was > comparable to Microsoft's domination of software in the 1990s. It's easy for us Auld Farts to forget that today's young hotshots weren't around back then. (What's even more frightening is how many people have never lived in a world without Microsoft.) > One could also claim that the standardisation of twos complement for > integers and signed magnitude for floating-point was settled at the > same time and for the same reasons. > > It may not have been ABSOLUTELY certain that people followed IBM > (after all, we didn't go with EBCDIC), but it was damn close to it. Perhaps this isn't the best example. At the very least, IBM needed interoperability with all those ASCII-based systems out there - hence products like their 3101 terminal. It was all those non-IBM-mainframe systems springing up like weeds around the big blue monoliths that eventually supplanted EBCDIC in general usage. Taken from Ted Nelson's "Computer Lib": "ASCII and ye shall receive." -- the computer industry "ASCII not, what your machine can do for you." -- IBM -- /~\ cgibbs(a)kltpzyxm.invalid (Charlie Gibbs) \ / I'm really at ac.dekanfrus if you read it the right way. X Top-posted messages will probably be ignored. See RFC1855. / \ HTML will DEFINITELY be ignored. Join the ASCII ribbon campaign!
From: Nick Maclaren on 7 Mar 2007 18:26 In article <esnf84$1lsu$1(a)gal.iecc.com>, johnl(a)iecc.com (John L) writes: |> |> >One could also claim that the standardisation of twos complement for |> >integers and signed magnitude for floating-point was settled at the |> >same time and for the same reasons. |> |> Twos complement, sure. Floating point, heck no. Other than the S/360 |> clones, the only maker I can recall using the IBM floating point format |> was Data General. Reread what I said. Did you never use systems with twos complement floating-point? Regards, Nick Maclaren.
From: Quadibloc on 7 Mar 2007 18:56 Rich Alderson wrote: > A *really large* PDP-10 has (note tense) 128MW (and you meant 4MW, not 4KW, > above). That's an XKL Toad-1 with 4 32MW boards (minimal memory on system is > 32MW). The PDP-10 did not die with DEC. You mean a PDP-10 - compatible computer. Maclean's toothpaste may have prevented tooth decay with sodium monofluorophosphate too. But Colgate could still run those "Only Colgate has MFP" commercials in Canada, because MFP was a trademark of theirs! If DEC didn't make it, it isn't a DECsystem 20. (The PDP-10 actually died *before* DEC did. On the other hand, Hewlett-Packard is still very much alive last time I looked.) John Savard
From: Quadibloc on 7 Mar 2007 19:00
John L wrote: > >One could also claim that the standardisation of twos complement for > >integers and signed magnitude for floating-point was settled at the > >same time and for the same reasons. > > Twos complement, sure. Floating point, heck no. Other than the S/360 > clones, the only maker I can recall using the IBM floating point format > was Data General. .. Texas Instruments used it in their 990 series computers. Also, some "near-clones" used it - the Sigma computers from XDS (with one change) and Interdata. But the use of sign-magnitude for floating-point could have resulted from copying IBM even if the System/360 floating-point format was not widely copied. Both the PDP-10 and the Univac 1108 had floating-point formats closely modeled on that of the 704; in fact, today's IEEE 754 standard can be traced back to the 704. John Savard |