Aucbvax.6103
fa.info-terms
utcsrgv!utzoo!decvax!ucbvax!info-terms
Sat Feb 6 17:02:22 1982
8 1/2 X 11 Screens
>From BERN@MIT-MC Sat Feb 6 04:16:34 1982
There is the Ann Arbor Ambassador terminal with maximum 60 (pretty
sure not 66) lines. But it suffers from readability. Price is
about reasonable. Your best bet would be the BBN Bitgraph
(bitmapped) which can hold as many as 128 lines (semi-readable) or
64 lines very readable. It's price should come down. The reason
for the 24 line standard (I believe) is the horizontal scan rate
which is a hold over from the NTSC TV standard. The standard gives
you about 525 raster lines per 2 interlaces, or 262 raster lines per
interlace. With 10 dots separating two lines, you get 24 (or 25)
lines (some horizontal raster lines are always blanked). The Ann
Arbor uses both interlace thus can give you 48 lines readable, and
then at a smaller font it gives you as many as 60 lines.
Yes, the 24 lines is a holdover. It should go, but then if you
don't do it the Ann Arbor way, you will make it non-standard (w.r.t.
NTSC, i.e., the ordinary black-white TV tubes and their deflection
circuitry) and then prices go up because volume comes down.
However, in the long run I would think the Ann Arbor would become
the intermediate standard before you get into full fledged bit
mapped (1024 raster lines a la Bitgraph) which may come sooner than
we expect.
The major problem with bitmapped terminals is that scrolling speed
is inverse the size of the scrolled region and is relatively slower
than character generated terminals. There are hacks to provide
hardware assist for scrolling, but in my opinion they are
unnecassary if the software does wrap-around or scrolls by multiple
lines at a time.
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