Re: CBM900 hard disk timeout

From: Michał Pleban <>
Date: Fri, 22 Aug 2014 17:45:45 +0200
Message-ID: <>

Martin Hoffmann-Vetter wrote:

> Then this means "controller initialization failed". ;-)

That is very much possible ;-)

> I would say, the drive initialize to track 0. The first sectors are on track 0. This must be the partition table at sector 1. So the real partition starts at sector 2.

That makes perfect sense.

The computer apparently never tries to read sector 1, or at least it is
not saying anything about that. It start with sector 2. But let's worry
about it later.

> So it's possible, the drive can't step to a specified track. This is the difference between ST412 and ST506. ST412 drives used buffered seek. All step pulses are counted and the drive will moved in one pass to the specified track. ST506 drives seek with every step pulse. Is it possible to switch the WD1003 or the hard drive between buffered and unbuffered seek? In buffered seek you need a SEEK_COMPLETE signal on the control port. If the drive don't send it, it's possible the controller detect a timeout! 

Good point. I noticed that some WD1003 PC cards have jumpers to choose
one of these stepping mechanism, but the problem is the WD1003-CMD has
no jumpers whatsoever.

> Can you step the drive with pulses on the control port manually? You
need a direction signal (low = inward, high = outward - toward track 0),
too. After the drive is powered on the READY and SEEK_COMPLETE signals
must be active.

Great idea. I will build some circuitry to do that when I get back home.

> Did you have ask WD?

I have searched their website and found only documentation for WD1003 PC
cards. I will send them an email.


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Received on 2014-08-22 16:00:38

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