Re: Troubleshooting the disk drives in a 8296D

From: Marko Mäkelä (
Date: 2004-12-05 13:11:19

On Sun, Nov 21, 2004 at 08:10:35PM -0500, William Levak wrote:
> On Sun, 21 Nov 2004, Marko [iso-8859-1] Mäkelä wrote:
> > Remember the CBM 220 (a.k.a. 8296D) whose drive analog board was broken in
> > two halves?  Well, I ended up buying it, and thanks to Ruud Baltissen, the
> > system now has a healthy-looking analog board.  However, the drives still
> > do not work.
> > 
> > When I power up the system, the disk status LED between the drive slots lights
> > red for a while (approximately 1 second), then green for approx. 1 sec, and
> > then it flashes red once very quickly.  The LEDs next to the drive slots
> > do not light up.
> This sounds like a ROM error as the initialization is not completed.

I finally got around to setting up a PC equipped with a RS-232 port, next to
the CBM 220 and a C2N232.  I dumped the area $8000-$ffff of the drive memory,
and found two identical 16 KiB images (i.e., $8000-$bfff is a mirror image
of $c000-$cfff).  The $c000-$dfff ROM is identical with 901887-01, and the
$e000-$ffff ROM is identical with 901888-01.  I didn't get the chance to
dump the FDC ROM yet.

> > When I power up my 8250, the middle LED does approximately the same thing,
> > but when it blinks red quickly, also the two LEDs at the drive slots blink
> > once.
> This is the normal initialization.

Do you think that it could be the FDC ROM?  I'll next adapt your
"read6530.lst" to write the data to screen memory and dump it from there.
(For some reason, cbmlink's drive memory access facilities deadlocked.)


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