Re: 1541 – two computers, one drive

From: Anders Carlsson <*anders.carlsson_at_sfks.se*> Date: Wed, 25 Mar 2020 15:44:18 +0100 Message-ID: <2ba3f483-e9c1-b02c-945c-4d899263b51e_at_sfks.se> · anders.carlsson_at_sfks.se

silverdr_at_wfmh.org.pl wrote:
> "It was also possible, without requiring a VIC-switch, to connect two Commodore 64s to one 1541 floppy disk drive ..."
>
> Has anyone tested that? Is that a fully deterministic/reliable behaviour?

As far as I know, you need to release the CLK (or is it ATN?) line after 
using the drive in order to not lock up the chain:

C64: POKE 56576,PEEK(56576) AND 239
Plus/4: POKE 1,PEEK(1) OR 1
VIC-20: POKE 37137,PEEK(37137) OR 3

I used to have my Amiga 500 with a parallel cable connected to 1541-II 
and then either a C64 or VIC-20 also connected. By issuing a such POKE 
from the CBM side, I was able to store files on the disk and then load 
it on the target computer.

A bit clumsy and failure prone if you forget the POKE so you end up in a 
deadlock but for shorter periods of operation it seemed to work.

Best regards

Anders Carlsson