jms@tardis.Tymnet.COM (Joe Smith) (01/12/91)
In article <1990Dec31.091243.470@phoenix.pub.uu.oz.au> proff@phoenix.pub.uu.oz.au (Frederick Solidus) writes: >In <7357@sugar.hackercorp.com> peter@sugar.hackercorp.com (Peter da Silva) writes: >>It's a design flaw in the standard 3.5" interface. Apple doesn't have the >>problem because they don't use standard drives, and IBMs don't have >>the problem because they don't detect disk changes at all. > >Still, I don't see why the read/writte status just carn't be scanned. That >would inform if there was a disk change. The problem is in the way that the original floppy manufacturers decided to implement the "disk changed" signal. To quote the Amiga Hardware Manual: CHNG-(Pin #11) A selected drive will drive this signal low whenever its internal "disk change" latch is set. This latch is set when the drive is first powered on, or whenever there is not diskette in the drive. To reset the latch, the system must select the drive, and step the head. Of course, the latch will not reset if there is no diskette installed. [The signal is latched in case one floppy is removed and another one inserted while the Operating System was not looking at the disk drive. (These 3.5 inch drives were not designed specifically for the Amiga.) The WRPRO (write-protect) signal is not an accurate indicator of disk presence.] So, the Amiga can detect immediately when the floppy is removed. However, there is no signal from the disk drive that says when a new floppy is inserted. The only way to detect the presence of a floppy in the drive is step the heads to the next track and see if that operation has caused the CHNG signal to become de-asserted. -- Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C51 | BIX: smithjoe | CA license plate: "POPJ P," (PDP-10) San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga 3000 speaks for me."
thad@cup.portal.com (Thad P Floryan) (01/13/91)
jms@tardis.Tymnet.COM (Joe Smith) in <1412@tardis.Tymnet.COM> writes:
[...]
So, the Amiga can detect immediately when the floppy is removed.
However, there is no signal from the disk drive that says when a new
floppy is inserted. The only way to detect the presence of a floppy
in the drive is step the heads to the next track and see if that
operation has caused the CHNG signal to become de-asserted.
But you've omitted a VERY important point that's exploited by NoKlickStart and
that is that SOME drives can be stepped OUTWARDS to reset the latch and are
smart enough to realize they're already at cylinder 0 and thus won't do any
actual movement and thus are silent.
Even with MY bad hearing, clicking floppies on the Amiga are a nuisance I will
NOT tolerate. I use "good" floppy drives and NoKlickStart as it's been posted
to comp.binaries.amiga and probably on abcfd20.larc.nasa.gov
Keeping floppies in the drive solely to suppress clicking is absurd, as all
the tiny springs and whatnot may develop a "set" and not be at full temper
when most needed.
Commodore should find a floppy-drive manufacturer who's willing to cater to
the requirements of a company that's already produced over 2 million systems
(Amiga) and custom-make, if necessary, the logic, sensor(s), whatever are
required to produce a computer system that not only acts "professional" but
also SOUNDS professional (e.g. no tacky tick...tick...tick...)
Thad Floryan [ thad@cup.portal.com ]jesup@cbmvax.commodore.com (Randell Jesup) (01/15/91)
In article <1412@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes: >So, the Amiga can detect immediately when the floppy is removed. However, >there is no signal from the disk drive that says when a new floppy is >inserted. The only way to detect the presence of a floppy in the drive >is step the heads to the next track and see if that operation has caused >the CHNG signal to become de-asserted. Almost right. The Amiga still has to poll to notice a disk removal, though there's no need to step the head. It must select the drive, and then examine the state of the CHNG signal. Also, due to a few drives we once used, we have to wait an extra 12us after selecting the drive before examining the signals, since a manufacturer over-buffered or under-drove them (they don't move for a long time, then slowly slope down over several hundred ns). -- Randell Jesup, Keeper of AmigaDos, Commodore Engineering. {uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.commodore.com BIX: rjesup The compiler runs Like a swift-flowing river I wait in silence. (From "The Zen of Programming") ;-)