Re: High Resolution Question

[dempson@actrix.gen.nz (David Empson)]

Aaron Pulver <apulver@mhtc.net> wrote:

> Also from the very same AppleFritter site:
> 
> "Edmond's Apple I Specifications
> ...
> VIDEO OUTPUT: ... Format: 40 char/line, 24 lines, with automatic scrolling
> ...
> Display Memory: Dynamic shift registers (1K x 7)"

Does anyone have any further information on this "dynamic shift
register" arrangement used by the Apple I's screen?

My recollection (probably from reading something in a magazine in the
order of fifteen to twenty years ago) is that the Apple I screen
operated pretty much like a parallel connection to a dumb terminal: data
to be output to the screen was stored in a single memory location, and
the output position was updated automatically in hardware.  There was
presumably some way of doing a "new line" operation (outputting
sufficient spaces would have done the trick if there wasn't an easier
method), and clearing the screen.  I expect it implemented the cursor in
hardware as well.

The only feature this has in common with the Apple II text screen is its
resolution.

Even if I have the details wrong, I'm sure that it was a lot simpler
than the Apple II text screen, and it wasn't able to support random
access to arbitrary positions on the screen.

-- 
David Empson
dempson@actrix.gen.nz