vico wrote on 2025-04-04, 17:20:

It's a bit disappointing that the parallel cable has such poor transfer capacity, but I appreciate all your clarifications. Unfortunately, my DELL Latitude LM doesn't have a network port, only a PCMCIA modem card.

Back in early 90s, in my home country, Kirschbaum Netz was very popular.
It was a localized version of Little Big LAN, essentially.
Anyway, it was popular exactly because unlike Novell Netware it could operate via ordinary serial and parallel connections (in addition to using NE2000 and ARCNet cards).

I remember how my dad had built many serial null-modem cables for his customers, because they felt that they needed a network,
but same time were afraid of the investment (networking as concept was still alien at the time).
So they ended up with a network of PCs being daisy-chained via serial/parallel ports.

Let's imagine this, a network built out of long, ordinary PC cables instead of coaxial cables or twisted-pair cables! ^^
The closest that comes to mind was the serial LocalTalk/PhoneNet wiring of Macintosh platform.

PS: I vaguely remember there were two schemes/standards for handshaking lines (RS-232). RTS/CTS and DTR/DSR.
In DOS gaming, RTS and CTS seem to have been a thing, whereas in early 80s or CP/M era the DTR/DSR pair was common.

Speaking under correction, though.
I merely mention it, because modern null-modem cables may miss support for older software.

Edit: I forgot. There also was Kirschbaum Link, which was simpler or lower end than Kirschbaum Netz.
My memory about is very limited, though. It was more of a file transfer software, K. Netz also supported printers etc.

I am reminded of old xircom pocket ethernet devices.

These were 8bit 'network cards' that lived on the parallel port, and were popular with vintage laptops. They did bnc coax, and twisted pair 10base.

I am half surprised that modern reproductions havent been made.

I've always been curious about those, anyone have any throughput measurements?

You can ask mbrutman? He's used/tested them on various systems.

wierd_w wrote on 2025-04-04, 19:21:

I am half surprised that modern reproductions havent been made.

I think that's because of PCMCIA slot and its successors.
They were meant to replace ISA slots as found in some 286/386 laptops from late 80s.

PCMCIA also aimed at the desktop market, that's why some Amigas had such slots, as well.

That's why new LPT devices never came to be again, I think.
Why using a slow parallel port if you can have access to an full-fledged ISA/PCI/PCIe slot?

The Computer Chronicles had some episode(s) in which PCMCIA slot concept had been explained a little bit, I think.

wierd_w wrote on 2025-04-04, 21:10:

You can ask mbrutman? He's used/tested them on various systems.

No need to ask, even - http://www.brutman.com/mTCP/mTCP_Performance.html

It's actually surprising how slow access to parallel port hardware is.

At one point I was having some issues with parallel transfers in DDLINK,
it eventually turned out to be a register that wasn't getting preserved
in a certain fairly obscure code sequence...

But.. in the process of debugging it, I had modified a bit of code
that avoids "race conditions" on input from the LPT port to "extra
check":

1        IN      AL,DX           ; Read port
2lin1:   MOV     AH,AL           ; Save
3        IN      AL,DX           ; Read again
4        CMP     AL,AH           ; Stable?
5        JNZ     lin1            ; No, wait
6        IN      AL,DX           ; \  I had
7        CMP     AL,AH           ;  > added these
8        JNZ     lin1            ; /  lines

Thinking that this wasn't a bad thing, and that those extra three
instructions wouldn't be at all significant in the total transfer
time, I had left them in.

I just did some testing... With the code "as above", transferring a 1MB
(1,048,576 bytes) file takes 24 seconds = 43.6k/second

With the above marked three lines removed (no other changes), the transfer
takes 18 seconds = 58.2k/second

Just goes to show how slow access standard (on-board in this case) LPT port
hardware is! (This was using older P3 and P4 systems - not sure what the
"official" speeds are but P3 BIOS shows "CPU clock" as 133 (with "Setup CPU
speed" at 466), and P4 BIOS shows "CPU clock" as 200)