On Thu, Mar 15, 2012 at 12:20:15PM -0700, John R Pierce wrote:
> On 03/15/12 6:31 AM, James B. Byrne wrote:
> > I eventually managed to read the tape at 1600 bpi in raw
> > block format and from the headers determined that the
> > encoding was EBCDIC and that the tape had been created on
> > a CDC machine.
> if it was from a 70s' vintage CDC system, I'm sort of surprised it
> wasn't BCD, not EBCDIC... BCD was an earlier 7 bit character
> code. lucky that was 9-track, the CDC stuff I remember used 7-track
> tape, even MORE unobtanium.
> On 03/15/12 6:59 AM, firstname.lastname@example.org wrote:
> > c) had you asked me, and only telling me the above, I would have told you,
> > with 95% (at least) confidence, that it was EBCDIC.
> actually, I dealt quite a bit with 9-track ASCII tape from that era...
> DEC, Data General, HP, etc systems were all ASCII based. I'd only
> expect EBCDIC if it was from an IBM system, or one of the clones like RCA.
On our CDC system back in the previous century, it is true that
BCD was common, but EBCDIC could be selected as could ASCII. I
think ASCII with parity was default on 9 track.
But, on the 7 track, it used a 6 bit character set that excluded
lower case, eg was only upper case alpha, decimal digits and special
characters. I don't remember how binary was encoded on them,
probably pairs of 6 bit 'bytes' since the PPs were 12 bit 'machine'.
> fun bit of personal trivia... my wife's first job out of college was at
> DEC as a new Technical Writer, and her first assignment was to sort out
> the Mag Tape subsystem for VAX/VMS 1.x and write first the internal
> design specs, then users documentation. VAX/VMS had excellent mag tape
> support, just as 9-track mag tape was fading into oblivion.
> fun bit of trivia #2: my very good friend is a hobby-machinist, builds
> scale working live steam trains when he's not doing hardware/software
> consulting jobs.... he has a vintage bridgeport mill which he grafted a
> 100VDC servo motor out of a high speed Ampex 9-track take drive as the
> Bridgeport came with a 3-phase motor and its rather hard to get 3-phase
> AC in a residential garage workshop
This DC motor is smooth,
> powerful and quiet, and lets him run the mill at variable speeds without
> messing with the V-belts.
> john r pierce N 37, W 122
> santa cruz ca mid-left coast
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