Interconnecting classic computers

[Ray Arachelian]

Tony Duell wrote:
> Thypicallyt they were used with IBM-compatible PCs and plugged into the 
> serial ports. There were many schemes, but the simplest was something 
> like : 
>
>
>
> TxD o---->|--------+----------------o Network line
>                    |
> RxD o--------------+
>                    |
> DTR o-/\/\/--------+
>
> SG  o-------------------------------o Network ground/common
>
>   
This reminds me of the good ol'e AppleTalk, later renamed to LocalTalk 
once they had their ethernet version.

I had a very nice, small network at home, long before ethernet, and it 
worked very nicely.  Connected a Mac XL, IIcx, a PC, and a TI microlaser 
printer, all by phone cabling.

I had to buy something called a CoActive plug which seemed to me to be a 
parallel port to Z8250 interface (since PC UARTs wouldn't go as high as 
230Kbps) and had custom software to talk to AppleTalk.  Of course, 
filenames were munged at 8.3, since this was the good old (or rather bad 
old) DOS days.

It's funny how they use CSMA/CA on this network instead of CSMA/CD, and 
when ethernet came out, they continued to use the same protocol until 
nearly modern days where they switched to encapsulating Appletalk 
packets inside TCP/IP frames. 

I was almost like they were re-inventing Ethernet. :-)  I suppose they 
could have actually ran ethernet over phone cables, but probably someone 
thought they had a better way to control collisions; perhaps they did.  
Of course there was nothing but trouble with early Ethernet switches and 
EtherTalk since they continued to use CSMA/CA for quite some time.

I guess there's nothing quite like the not invented here syndrome.