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From: hans@nlgvax.UUCP (Hans Zuidam)
Newsgroups: comp.sys.amiga.tech
Subject: Amiga 500 external floppy disk failure
Message-ID: <238@nlgvax.UUCP>
Date: 9 Aug 88 22:43:15 GMT
Reply-To: hans@nlgvax.UUCP (Hans Zuidam)
Followup-To: comp.sys.amiga.tech
Organization: Philips Research Geldrop
Lines: 39

This is for a collegue of mine...

------------------------------------------------------------------------

From: Andrew Dickman (Philips Telecommunications and Data Systems)
Subject: Amiga 500 external floppy disk failure

We have an Amiga 500 which (after booting) thinks it has 4 disk drives:
1 internal and 3 external. The three external ones are marked "BAD".

What happens during power-up is the following (according to the manuals):

	1. Each possible external drive is selected and it's motor-on
	   line is pulsed.
	2. This then informs the drive to send it's identification.
	3. The Amiga reads this bitstream back and depending on the
	   returned value it determines the drive type:

		$FFFFFFFF  3.5"
		$55555555  5.25"
		$00000000  no disk

Now when the software boots, it goes through all detected disks and tries
to find out what they are (KICK, DOS). Because the drives are not there
they are marked bad. Booting takes ages this way.

We suspect that's it has something to do with pin 1 on CN5 (_RDY) (Does
the "_" means active low?). This line remains low during startup.
Adding a 4K7 pull-up resistor 4K7 doesn't.

If anyone has a hint on where to look or what to do, we are greatfull.

					Andrew

-- 
Hans Zuidam                                    E-Mail: hans@nlgvax.UUCP
Philips Telecommunications and Data Systems,   Tel: +31 40 892288
Project Centre Geldrop, Building XR
Willem Alexanderlaan 7B, 5664 AN Geldrop       The Netherlands