<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
On 03-Sep-18 11:52, Mark Pizzolato wrote:<br>
<blockquote type="cite"
cite="mid:03006E3FC39B5A48AB9DBCCC101090A8344A084C8C@REDROOF2.alohasunset.com"><br>
<pre wrap="">Interesting...
I'm a little confused though. I certainly understand using the GT40
as a standalone system to run Lunar Lander. That's great fun.
Meanwhile, if the GT40 could be some sort of terminal to some other
system, how was it connected to that other system? Serial line via the
DL device?
Also, how/where was the LK40 keyboard connected to the system?
Through the DL device? Was there more than one DL device?
- Mark
</pre>
</blockquote>
<br>
The GT40 stand-alone is a toy. Lunar lander was just a demo.<br>
<br>
In real life, the GT40 was used as a(n expensive) graphics terminal
(~$10-15K IIRC), most often for the -10. CAD systems, such as SUDS
and (e.g. circuit) simulations used it. You could add arbitrary -11
peripherals, but that wasn't often done - not cost effective. The
host provides the disks & application computes - the GT40, which
is a vector display + lightpen & keyboard offloads the display.
The GT40 pushes display list execution to a DMA processor, which is
similar to the VB10C (VR30, & type 340), it executes display
lists. (See the DIS device in the TOPS-10 Monitor calls manual for
details of those devices.) The GT40's -11 could provide an
additional level of abstraction between the host & display
processor. Interpolation; step & repeat; managing the light pen
interactions (e.g. drag, draw line, etc).<br>
<br>
In addition the GT40 could be located remotely from the host - not
quite office environment, but less of a computer room than the -10.
And while expensive by today's standards, moving the overhead off
the -10 was worthwhile. I believe the CAD group had clusters of
them talking to the -10.<br>
<br>
It had a long life - about 1972, serviced until 1995. If you needed
the capability, you could afford it. But you didn't buy one
casually.<br>
<br>
For most purposes, the GT40 was superseded by devices like the VT105
(VT100 + b/w graphics), VT125, GiGi, & VT240. But those are all
raster scan devices - which can't match the quality of a vector
display. And none of them had a lightpen.<br>
<br>
Brochure scans:<br>
<a class="moz-txt-link-freetext" href="https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-3.jpg">https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-3.jpg</a><br>
<a class="moz-txt-link-freetext" href="https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-4.jpg">https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-4.jpg</a><br>
<a class="moz-txt-link-freetext" href="https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-5.jpg">https://web.archive.org/web/20060509012428/http://d116.com/dec/gt/GT40-5.jpg</a><br>
<br>
More technical info:<br>
<p><a class="moz-txt-link-freetext" href="http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-11-HGTGA-B-D%20GT40-GT42%20User's%20Guide.pdf">http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-11-HGTGA-B-D%20GT40-GT42%20User's%20Guide.pdf</a></p>
<p>The keyboard uses a ~110 bps 20ma current loop interface. It
connects to the standard console interface to the 11/05(11/10). I
don't recall what was done with the output side - but I suspect it
was brought out to the usual molex connector so that standard -11
diagnostics could be run.</p>
<p><br>
</p>
<p><br>
</p>
</body>
</html>