| Walter Spector 2005-08-30, 6:59 pm |
| "Dr Ivan D. Reid" wrote:
> ... Most of the solutions were found by
> poring through the FORTRAN manual and probably some OS manuals -- the
> consulting staff were at a total loss...
That doesn't suprise me. CDC systems were incredibly elegant in many ways,
and incredibly disorganized in other ways. There were at least 4 or 5
different ways of doing full ASCII - depending on printer/magtape/tty,
OS, OS level, etc. And as you note, the documentation was somewhat scattered.
> I found out about the 12-bit
> output and that I had to pad the 8-bit binary code into those bytes. Then
> there was the fact that multiplication only worked up to 48 bits so I had
> to use successive adds to shift the first four bytes along to add in the
> fifth.
I think there is a compiler option to do full 64-bit integer mults/divs.
But the 48-bit instruction sequences are a *lot* faster, and good enough for
most purposes. (I use present tense because there are a few retro-computing
buffs running CDC software on emulatators... :)
> Then the output would mysteriously die mid-tape, and after some
> puzzling I discovered that an all-zero 12-bit byte was taken as
> end-of-file (IIRC, or was it two in succession?) so I changed to making
> the four MSBs in each byte all ones so that NULLs weren't misinterpreted as
> EOF.
Depends again on OS and device type. But IIRC Adelaide ran NOS/BE, and you
probably had to set bit 11 of each 12-bit byte.
Back in the late 1970s, I ported some graphics routines to run on CDC
using Tektronix 4010/4014-style storage scopes. Once I figured it out,
the code for pushing characters transparently through the OS on the CDC
gear was easy. Much easier in fact, than it was under VAX/VMS. This
was on VMS 1.0 and the stupid RMS kept gobbling up and reinterpreting the
control characters. (I eventually used direct QIO calls to get the data
through. No thanks to DEC though. Their VMS field/tech support was abysmal
at the time.)
> ...and then it ran happily ever after and my development of software
> for the Mawson Antarctic Interferometer became much easier..
Hooray!
Walt
(w6ws att earthlink dott net)
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