> And it reminded me of some of my own past exploration into systems that did > RS232 without an UART. > > One example is the NEC PC-8001 (system from about 1979). I recall having > trouble getting it past 600 baud for some reason.
Infamously also the Commodore 64, which a) had the wrong prescaler value for 1200 baud in ROM and b) wasn't particularly efficient, such that software 2400 baud routines were widely used in place of the ROM ones. Part of b) was a well-intentioned but incomplete and not well-implemented attempt at acting like a 6551 ACIA in software. Until those 2400 baud routines started appearing, most people drove the system at 300 baud and no faster (admittedly the VICMODEM and 1660 were only 300 baud themselves). With a real ACIA cartridge, or a system like the Plus/4 which had an ACIA built-in, the 64 had no trouble with faster rates. I used a Turbo232 with a 56K modem for awhile. -- ------------------------------------ personal: http://www.cameronkaiser.com/ -- Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckai...@floodgap.com -- Actually, we can overcome gravity (just not the paperwork involved). -------
