Re: Commodore 65 and DIN8 cable

Date: Fri, 29 Jan 2016 11:09:24 +0100
Message-ID: <>
Open ended (and possibly also unshielded) wires never do any good to signal quality. They are nice antennas, which will add whatever electromagnetic smog flies around you to the signal but will also try to radiate your signal out. None of these helps. Termination - the drive should provide it, similar to what was a standard in SCSI devices. Still, I wouldn't bet all of them do. I wouldn't be surprised if some were cost reduced because it still worked in basic cases. How to make own? Either check the older, still standard compliant implementations or maybe checking the original SCSI devices? 
Sent from mobile device. Please have understanding.

On 28 January 2016 16:16:59 CET, "Michał Pleban" <> wrote:
>I started a project to re-create the 1565 external floppy for the
>Commodore 65. The floppy is supposed to be attached to the computer via
>a mini-DIN8 cable.
>So I purchased a cable and stuck it into the floppy port of the
>(of course I had to solder a mini-DIN8 connector there first). The
>internal floppy stopped working. When I remove the cable, the floppy
>works again. Hmm.
>I suspect that this happens because the "disk read data" and "disk
>data" signals are exposed directly on the floppy port, and they are
>shared among all floppies. So it looks to me that some stray signals
>being induced on these lines in the cable, and they confuse the disk
>controller enough to throw disk read errors. This would be similar to
>Bil's story about the data bus of C116 being exposed directly on the
>joystick port.
>To confirm this, I bought a shorter cable. The original cable had 3m,
>and the new one has 1m. The situation improved somewhat - now the
>works about 20% of the time. With a yet shorter cable I could probably
>make it work even better, but that's the shortest cable I found on
>and besides it's not really a solution I'm looking for.
>My extremely limited knowledge of analog electronics tells me that
>perhaps I need termination on the end of cable. Is this a good guess?
>And if yes, is there any way to find the correct terminating resistor
>value apart from soldering a potentiometer between GND and DISK_RD and
>patiently trying for the best value?
>Also, at some point of course a floppy drive will be attached to the
>of cable - what should happen with the termination then? I suppose it
>should be removed but will the floppy drive itself act as a good
>And why this effect does not exhibit itself in PCs and other computers
>where the floppy cables also tend to be long (or maybe it does)?
>       Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list
Received on 2016-01-29 11:00:10

Archive generated by hypermail 2.2.0.