On Tue, Feb 11, 2025 at 9:49 AM ben via cctalk <[email protected]> wrote:
> On 2025-02-11 9:32 a.m., Peter Corlett via cctalk wrote: > > > 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. > 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 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? > 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 > > 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) :). > > >
