14 Sep
2005
14 Sep
'05
4:10 p.m.
Just to add more lore:
And I'll add some more, I still use such machines...
The floppy controller and floppy drive were very
optional on the early
PC, and a rather pricey option. There was a cassette cable for less
The cassette port pinout ios the same as that for a TRS-80 (M1, M3, M4,
M100, CoCo, etc) (and for that matter a Dragon). The same cable works
with both.
wealthy users. And on any IBM machine up to the late
XT era, if you
boot it up with no disk in the A drive or no floppy hardware at all
installed, it will boot into 'cassette basic'. (does anybody know if the
PC-AT had cassette basic resident in ROM?) My PC Convertable will do
Yes it does. AFAIK all IBM PC, PC/XT, PortablePC (which is the same
mainboard as the PC/XT) and PC/AT machines have ROM BASIC. I am typing
this on a much hacked 8MHz IBM PC/AT, and it has BASIC in ROM.
so. Sadly, you can't save or load anything into
'Cassette Basic' on the
Convertable or models later than the PC as there's no cassette
interface. I wonder if anybody has ever 'back ported' the Cassette port
to an ISA bus card?? (not that it would help on the PC Convertable, of
course.
From what I remember, cassette I/O is handled via one
of the software
INTs (INT 15, maybe, I can check). The routines are only present in
the
PC BIOS, on all later machines, the routines return (maybe setting an
error flag, I forget).
But there would be no reason that a BIOS extension ROM couldn't intercept
this INT vector and perform suitable I/O, either to a cassette recorder
or to, say, a paper tape punch/reader. I have sort-of thought about
making an ISA card for the latter with the necessary ROM on it, but I
haven't got a round tuit.
-tony