"Paul" schreef in bericht
news
Linea Recta wrote:
Some time ago I mounted a new SATA hard drive in my PC, as I mentioned in
this group. The hard drive is working fine.
However, yesterday I wanted to read a floppy disk... but the floppy drive
seemed stone dead. In Windows explorer kept telling me to insert media
but the floppy disk was in alright. Tried another floppy disk and still
no media was found.
Took a look at Windows - system - devices and there it was: Drive A, no
explanation mark or nothing out of order. Looked under properties and it
said the device is working properly. (!)
Today I opened the case and had a look inside. It seems I had forgotten
to reconnect the power cable of the floppy drive after the hard disk
repair job. After connecting everything works OK again.
I'm very surprised though that Windows didn't give any clue that there ws
something wrong with drive A...

Floppy drives are "dumb" devices and don't have PNP
(Plug And Play) information.

The controller (logic block in the SuperI/O) on the
other hand, does have PNP. If you switch on the floppy
in the BIOS, when Windows boots, it "sees" the SuperI/O
logic block. But it cannot determine anything about
the floppy drive on the cable at that point.

CPU
|
|
SuperI/O ---- floppy cable ------ floppy_drive
(dumb device)

There are a couple flavors of drives. The Macintosh drives
had motorized eject, and they also seemed to have "Media Presence"
detect. (The inserted floppy pressed on a microswitch ot
something like that.) Windows floppies don't have motorized
eject, and maybe the first realization no media is present,
comes when the controller logic block goes to do a read,
and no transitions on /RDATA are seen. And then the notification
box "No Media" appears, which covers both actual no media being
in the drive, as well as, say, the head being ripped off the
arm of the drive.

But other than that, the floppy drive doesn't have a processor.
There is no "clever communication" between the floppy
and the SuperI/O. Unlike a SATA drive, where there is a processor
in the SATA drive, and packets travel over the data cable
as a communications path. The floppy just has a bunch of
mechanical control signals like Motor Enable, Step, Head Select.

Drive "A" appears in Windows, as soon as the SuperI/O logic
block is enabled in the BIOS. And I don't know if there is
an encoding in the registers there somewhere, indicating
how many drives are supported. There was some crazy scheme
at one point, to support up to four floppy drives. But I
don't remember the details. It's expected the user
will recognize their computer case has no floppy drive,
and program the BIOS logic block setting appropriately
(disable the SuperI/O FDC if no drives are equipped in the
computer case).

*******

If you rotate the floppy controller cable 180 degrees and
plug it in, the LED on the floppy drive should remain
asserted. And that would be a clue you screwed up. It
the power cable was disconnected, there would be a
pronounced lack of clicking, whirring, and LED flashing.

Paul



Thanks for your expert background information.
You're right: I missed the clicking sounds yesterday, but now all is OK
again.
As you can see, I don't use the floppy drive very often. I didn't notice it
disfunctioning from 6-1-2017 until yesterday...



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