14.3xxx MHz signal on the ISA bus (was Re: Help identifying a capacitor)
ethan.dicks at gmail.com
Fri Jul 20 19:37:14 CDT 2007
On 7/20/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
> The OSC signal was the 14.3xxx MHz master clcok signal in the PC and XT...
> It was used, of course, by the CGA card as the master clock for the video
> and colour cubcarrier timing. Some other cards used it, often divided
> down, as a master clock.
Is there a list anywhere of what cards tended to use that signal? I
ask because I manufacture the GG2 Bus+ bus adapter for the Amiga, and,
because that signal is on the ISA bus, the designer of the card
slapped a $3 oscillator on it to provide it. I have a number of
unassembled cards and, honestly, would like to leave that signal off
if there's no expectation of folks needing it.
These days, the most common use for an ISA bus on an Amiga are either
for Ethernet (NE2000 or SMC 80x3) or serial (8250/16550). There are
other drivers, but nobody really cares about those anymore.
Certainly, nobody I am aware of is hanging a CGA card off of an Amiga,
but there's no reason why it wouldn't work from a technical standpoint
(and the holes are on the board for the oscillator anyway).
So... after the AT faded away and folks were running EGA and VGA on
386s and up, was the 14.3xxx MHz signal still relevant, or just an
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