11 Feb
2025
11 Feb
'25
7:09 p.m.
On Tue, Feb 11, 2025 at 9:49 AM ben via cctalk <cctalk(a)classiccmp.org>
wrote:
Yea, 16550 compatible UARTs are still around, and go up to baud rates of
10Mbps at least in the embedded space where you often use it to jam in the
first bootstrap program (or the unbricking program).
Warner
On 2025-02-11 9:32 a.m., Peter Corlett via cctalk
wrote:
No. The 16550''s were good enough to do line rate 115200 on a 16MHz 386
under both FreeBSD and Linux (though the clist overhead was a little high
on FreeBSD in comparison to Linux).
The proper solution to dodgy PC serial port
performance was of course to
upgrade to the 16550 which had a FIFO which could buffer a few bytes
while
the PC got round to answering the interrupt.
It's not the greatest UART
and
adds novel failure modes, but it does have the
extremely useful property
that it is register-compatible with the 8250 and so older software can
still
drive it without needing to be patched.
I thought many 16550 had dud fifo's.
Interrupts under DOS was hit and miss.
The 16550 (at
1.8432Mhz) still has the same top speed of 115,200 baud,
but
that's just fine for the kind of applications
which use physical
RS-232-compatible serial ports such as dialup modems and serial mice.
RS-232
only guarantees up to 20 kilobaud anyway, and
anything faster is out of
spec
and works through luck. Fortunately, we had a lot
of luck by the late
1990s
when V.90 dialup came around. Want to go even
faster over long cable
runs?
We have
Ethernet for that sort of thing, and it's rather more reliable at
it.
Sneaker net with van is better yet, moving large data.(10 TB per tape) :).