[rescue] 10base2 Cable

[Patrik Schindler]

Hello Doug,

Am 07.04.2024 um 07:59 schrieb Doug McIntyre via rescue <rescue at sunhelp.org>:

> And even with a two device SCSI, you still needed to terminate each end of the bus.

This heavily depends on the length of the cable and if synchronous mode is used. Early Macs only had one physical bus. Termination took place on the disk, but not on the board. Spared the logic to disable termination-when-plugged for the external non-standard DB25 connector.

> you wanted to make sure both ends of the SCSI bus were terminated for best performance.

… and less transmission errors. Parity just cannot detect each kind of error and you might end up with defective data after a transfer.

Can't speak for RG58 cheapernet, because I've accumulated enough material to build and maintain a huge LAN. :-)  But I observed that the plug connections are rather flakey, maybe because of old age and oxides? I've had multiple occasions that the Cisco Router in front (with proper diagnostics compared to other equipment connected to the cheapernet segment) reported late collisions, despite data passing through. Just bending a cable in the 19" rack and the error was gone. Took me a while to isolate the faulty T-connector. Cleaning it with proper spray didn't help.

:wq! PoC