Re: [GDDM]

[dhandy@xxxxxxxxxxx (Douglas Handy)]

Rob,

>I think it was the 5292 screen, (not to be confused with the green screen 
>5291).  The 5252 screen is not supported on the 400.  The 5252 didn't support 
>a 24 line screen and looked like two terminals attached back to back.  This 
>way you could have rows of people working across from each other doing heads 
>down keying.  Probably the inspiration for the unionization of offices.

Close.    The 5292-02 was the color graphics display.  The 5292-01 was
color, but no graphics.  The 5292-02 was announced in May 1983 at the
same time as the S/36, and withdrawn from marketing in Aug 1986, at
the same time as the 5251-011 and 5251-012.  (Of course, by that time
I doubt they were still selling many 5251's. <g>)

What makes so many of these confusing was the model suffix.  EG, the
5291-1 had the big logic unit wider than the screen, and came part way
up the side.  The 5291-2 had the smaller logic unit and took up much
less desk space than other terminals available at the time.

The 5251 family was even worse.  It had:

 5251-001  Single-user 12x80 screen
 5251-002  Dual-user; each 12x80 (what you called the 5252)
 5251-011  Single-user 24x80 screen (the most "popular")
 5251-012  Remote controller with 24x80 and twinax ports
 5251-999  Not sure, but I think maybe ideographic?

The 5251-002 was kinda like the difference between the 3741 and 3742
diskette keypunch units.  Both the 5251-002 and 3742 looked like a
desk with keyboards on opposite sides.  The monitor was mounted
vertically inside the desk, not towards either user.  Mirrors cut the
screen image in half, and each user saw just their half of the screen
by looking in the mirror.  Each user got a 12x80 display.

Speaking from experience, they were a royal pain to work on.  I hated
them.  The 5251-001 was only slightly better.  You had a full-size
screen directly in front of you, like a 5251-011, but it only used the
top half...

One interesting thing about the 5292-02, is that the data stream used
a x'FF' as the leading byte of graphics streams instead of just the
range x'00' - x'3F', which is why you will sometimes see x'FF' listed
as part of the non-displayable character set along with values below
x'40'.

Geez, I must be getting old in computer years.  I've worked on all of
those models except the 5251-999.

Doug
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