30 Aug
2023
30 Aug
'23
10:08 p.m.
The probem with RF Modulators is that due to the National Television
Standards Committee standards for American television there wasn't
enough bandwidth to display 80 characters x24 lines (or 25 lines with
status). Generally 64 x 16 was the maxmimum that would be readable on a
standard black and white TV set. Any higher resolutions would either
cause the characters to "tear" or lose horizontal or vertical sync
completely.
That is why monitors were used. They were not bound by the NTSC
standards and were generally made for 80 x 25 or (even 132 x 25 with a
smaller character set).
On 8/30/2023 3:54 PM, William Sudbrink via cctalk wrote:
There were RF modulators. See the November 1976
review of the Poly-88 here
(on page 16):
http://cini.classiccmp.org/pdf/DrDobbs/DrDobbs-1976-11-12-v1n10.pdf
Note the reference to the "Pixie Verter". It is a little cheap circuit
board that takes the composite signal and modulates it onto channel 3. You
will find references to the Pixie-Verter in a number of publications and
user manuals for early video boards. The Matrox and the Cromemco Dazzler
and the Ohio Scientific documentation all reference it. David Ahl in his
"Saga Of A System" magazine article references it. With that, a TV, video
board, RF modulator and a parallel keyboard were much cheaper than any
serial terminal back then. The RF modulator was separate from the video
board (usually hung on the back of the TV) for noise reasons.
-----Original Message-----
From: W2HX via cctalk [mailto:cctalk@classiccmp.org]
Sent: Wednesday, August 30, 2023 3:39 PM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Cc: W2HX <w2hx(a)w2hx.com>
Subject: [cctalk] Silly question about S-100 and video monitors
Hi all,
I recently acquired an S-100 computer, and it came with a video card and a
keyboard (3rd party products, not originally equipped with these). I am
trying to figure out the benefits of having a video card and keyboard vs
just using a serial port and terminal. Certainly if the video card supported
graphics, that would be a reason to go that route over a terminal. As for
the keyboard, ok-maybe you need specific keys for a specific application.
But I don't understand the video monitor. I could understand maybe if there
was an RF modulator so that you could use a standard TV. That would save the
builder some money. But this computer just provides composite.
Other than graphics (and maybe some special function keys for an application
on a keyboard), why would an S-100 builder in those days opt to buy a video
card instead of a terminal?
Thanks for the bandwidth.
73 Eugene W2HX
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