On Mon, Nov 30, 2020 at 6:22 PM dwight via cctalk <cctalk@classiccmp.org> wrote:
> Is there a terminator on both ends. If not it is a static 15 ma. > There's a 220/330 terminator to +5V at both ends. The thevenin equivalent of one of these terminators is 132 ohms to +3V. A driver trying to pull this to 0V is going to have to provide 22.7 mA for a single terminator, but since it's doubly terminated, it will be 45.5 mA. They're only using 24mA rated drivers, which would be within spec if it wasn't doubly-terminated. SCSI uses double termination, but it also specifies minimum 48 mA drivers.