Ethan Grammatikidis wrote:
On Sat, 10 Oct 2009 04:15:59 +0800
W B Hacker <w...@conducive.org> wrote:
The only 'glue' needed was level-shifters - discrete transistors on my OSI
Challenger II, Motorola 1488 & 1489 diode-coupled-logic on everything up until
the 16XXX derivative of the 8250 was sucked into a 'bridge' chipset.
I remember being quite surprised by the first UARTs which had level
shifters on the chip, and they came out around 1993 or so didn't they?
As far as I know it was hardly possible to handle RS-232's 25V signals
on the same die as logic functions back in the 80s.
It wasn't 'hard' - especially since the 25V, though more common then than now -
was more likely to be between 7 to 15 volt, and 5V would usually get the job done...
But it just wasn't smart.
The separate circuitry - or even its PC board traces - all too often had to act
as a fuse - protecting the more expensive part of the kit with a cheap and easy
to replace module.
PCDOS was lousy at I/O, and Windows no better.
Linux either. Makes me sad. ;-J
Don't be too harsh. All Linux lacks is a decent kernel.
;-)
Bill
