On Mon, Nov 30, 2020 at 6:22 PM dwight via cctalk <cctalk at classiccmp.org>
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
SCSI uses double termination, but it also specifies minimum 48 mA drivers.