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Date: Sun, 5 Jan 2014 19:00:30 -0800
From: cclist at
sydex.com
To:
Subject: Re: MFM Control Signals and RD disk size
---snip---
So how do you tell if a drive is ready if the motor's not on? We
figured that keeping the drive motor on so long as a file was open for
writing, but that could be hours and hours. We eventually stumbled on
sampling the write-protect signal which didn't depend on the motor being
on. About every quarter-second, we sampled a drive's WP status if the
drive had any files opened for writing--if it changed, we halted
execution of the current application, put a message saying essentially
"Now put that disk back!" and sat on the beeper, turned on the motor and
waited for the drive to come ready again.
We never had another complaint on that problem again.
--Chuck
I wish they'd done that on the H89 Heathkits. If you were working
on a mounted disk and swapped the disk then wrote the files it
was a mess to unravel. My brother in-law did this once and I spent
several hours piecing fragments of files back together for him.
It was a good thing that it reused new space each time it wrote
to the disk. There was enough old pieces to recover most all of the
lost files.
Dwight