29 Jan
2008
29 Jan
'08
11:07 a.m.
Fred Cisin wrote:
The Victor 9000 (Sirius over here) does have a speaker. But it's not
driven by an 8253 (or 8354), in fact there is no such chip in the machine.
It's driven from a PCM codec chip. The bitstream for that comes from a
6852 (synchronous serial chip), the clock comes from one of the
counter/timers (line PB7???) of the 'User' VIA. Yes, the input side is
connected up as well, there's a pin header on the mainboard that can be
used to feed audio into the codec, and the bitstream from that goes to
the 6852.
Please don't ask me how to program that to make beeps ;-)
DOS calls will work for ANYTHING running MS-DOS,
including grossly
incompatible machines, such as Victor 9000 (Sirius)
Since one of my requirements is manipulating the PC speaker to sound an
arbitrary tone of arbitrary duration -- something that is not provided
by the BIOS or MS-DOS -- should I worry about "grossly incompatible"
machines? For example, does the Victor 9000 even *have* a speaker (or
8253 timer?)? That was also an issue with the AT&T PC
6300/Olivetti M24 if you were
using a monochrome monitor. It was monochrome CGA, but the monitor
would do things like _underline_ the text based on the attribute.
That, IIRC, is what a real _MDA_ card does.
-tony