2 Feb
2025
2 Feb
'25
7:47 p.m.
I came across the following more recent discussion:
2022-05-05 Bit banging on a Tandy CoCo1 - Wikistix
<https://www.stix.id.au/wiki/2022-05-05_Bit_banging_on_a_Tandy_CoCo1>
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.
Another example is the Color Computer 3. UltimateTerm 2.4 from 1987 could
bit-bang reliably 9600 baud (also Twilight Term from 1996). The CoCo3 had
a higher speed CPU option than its original. "bit banging" (imo) is the
host system doing the work of producing the start/stop bits on its own.
Which seems to be a "lost art" and why I've wondered if anyone has tried
bit-banging on a modern-day 3GHz system - but bit-bang onto what? They took
away our serial and parallel ports, like talking directly to a pin is now
taboo (literally a security risk, as some networks lock out CD drives and
USB also - "no information out" policies).
With the UART assist of the RS232Pak cartridge, a CoCo3 managed 115200 baud
using a very optimized NetMate terminal written in 2021. That's with the
6551 ACIA doing the serializing work (but I don't think it has any FIFO at
all).
I've been curious how much faster Interlink/Laplink/FastLynx really was
across a parallel cable (I've yet to find reliable bytes-per-second rate
info on those). On modernPC to modernPC I really was able to achieve
45KBps (bytes per second) on a 460Kbps serial connection (USB/serial
adapters; ones with 128 byte FIFO) using regular ZModem protocol.
There are "laplink-style-USB" things, but I'm still curious if we did
USB/parallel adapters and a classic laplink cable on two modern PCs, could
it surpass the 45KBps serial connection? Still a relic approach, as modern
day WiFi+samba should be faster. But where is any modern-make software to
even try?
-Steve
On Fri, Jan 31, 2025 at 2:13 PM Paul Koning via cctalk <
cctalk(a)classiccmp.org> wrote:
On Jan 31, 2025, at 2:18 PM, Wayne S via cctalk
<cctalk(a)classiccmp.org>
wrote:
Steve, remember that digital electronics ( I.E. integrated circuits like
uarts) weren’t around during the early days of data transmission. It was
all analog back then, coils, capacitors, and resistors, so then ideas
regarding fast transmission had to wait for the technology to evolve. Then
as ic’s became available, what you could do with them sparked new ideas.
Example: data compression within the modem using a microprocessor, thus
getting higher overall throughput than the theoretical maximum of just the
modulation rate.
True, though "digital electronics" and "integrated circuits" are
not
directly related. Digital circuits were first built with relays and with
tubes. What makes them "digital" is that they deal in ones and zeroes
rather than with continuous real-valued signals.
paul