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Phantom Drives and the SH204

Or...How My Hard Drive Did Funny Stuff with TOS 1.4

Glenn Dulin (COAC)

I had proudly, and with enthusiastic anticipation, installed TOS 1.4 in my
1040ST.  I turned on my hard drive and then the computer -- and oooooh! -- I
was impressed with TOS 1.4 and its new goodies.  I like it!  I like it!  But
wait...I noticed I was able to access a ramdisk that wasn't there (I had a G:
icon on the desktop).  I noticed DBman was accessing this drive that wasn't
there.  No errors!  Uh oh!  What are these ROMs doing to me?  I just spent
all
this money for a BIG BUG!  Were just MY ROMs faulty?  I hadn't heard anything
about this.

Later, I talked to a friend, Bob Kanski, who is in the club.  He asked if I
had tried just booting from floppies.  No, I hadn't.  He had TOS 1.4
installed
and, using floppies, it didn't show any signs of this malady.  I then booted
off floppy -- no problem, no phantoms.  That's fine, but I wanted to use my
hard drive.

In the meantime, Bob called another club member, David Powers, who had an
SH204.  When Bob got back to me, he taunted me and refused to tell me about
some new information he got from Dave until he had extorted a promise that I
would buy him a Coke.  After I gave in to this extortion, he told me Dave had
had the same symptoms when he had upgraded to TOS 1.2.  Hmmm!  I took my
computer to Bob Stiles, who has a 50meg ICD and everything worked fine...no
bug.

So, what's the cure?  It turns out that Atari's SH204 has a faulty chip with
the insidious and devious name of AMPAL written on it.  Even without a new
TOS, this chip does not report errors back to the operating system correctly.
You may do writes that didn't write correctly and no error would be reported.
It may do incomplete seeks or corrupt formatting or have uncorrectable data
reads.  It just so happens that this chip also allowed the phantom drive
syndrome.  I could have G: on the desktop but not installed, and whenever I
pulled up the file selector, I also got drives F: and H: that were not
installed or on the desktop.  And, yes, you could get a directory off of
these
drives.  It was, however, a directory of a real drive, usually the last real
one you accessed.

Enter Berkeley Microsystems and the ADE (Atari Drive Enhancement).  On Dave's
advice, who cured the problem with the ADE, I sent for the chip, and with
about ten minutes of work I had it installed in the SH204.  The installation
is easy, TOS 1.4 works like it should and the three of us are now living
happily ever after.

Even if you don't get your TOS upgraded, I would recommend getting this chip
for your SH204.  It's cheap insurance against a possible corruption of the
drive.

ADE Chip   $19.95 + $2 S&H
Berkeley Microsystems
P.O. Box 20119
Oakland, CA 94620
(415) 547-2191