5 Mar
2017
5 Mar
'17
12:04 p.m.
On 2017-Mar-05, at 11:27 AM, Chuck Guzis via cctalk wrote:
On 03/05/2017 10:41 AM, Mark J. Blair via cctalk
wrote:
In my limited experience of drives, but I expect it's typical, the write enable
is electro-mechanically latched: if the write ring is present at load, a solenoid
is activated which pulls the sense finger further in to hold the finger off the write
ring,
so it won't be a friction and wear point while running.
The solenoid is released at unload.
So, was the write enable state latched at some point in the loading
cycle on those drives? That surprises me, because I would have
expected the write enable sensor to interrupt write current as
combinatorial function on the drive, and/or pass sensor status up to
the formatter a combinatorial signal.
Yup. You loaded the tape, then bumped the "finger". As I mentioned,
this worked on 60x and 65x drives. Since the autoloaders closed the
door as part of the cycle, this probably didn't work for 66x.
This actually worked pretty well--you never ran the risk of leaving a
ring in inadvertently. The consequence of forgetting to enable write
was usually far less dire than mistakenly writing to a tape that was
supposed to be read-only.