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Re: Apple II ROM

Michael J. Mahon wrote:

Patricia Shanahan wrote:


Inspired by a History of Computing course I'm auditing, I dug my Apple
II out and powered it up.

It displays a screen with "Apple ][" at the top, otherwise blank. Reset
puts it in the monitor, which works correctly. It fails to enter Basic
or the mini-assembler.


So typing "Ctrl-B, Return" at the monitor prompt does not get you
to the BASIC prompt?


Correct. Also, "F666G" followed by a return does NOT take me to the
mini-assembler.

I am following the directions from the Reference Manual that came with
it, and as far as I remember everything worked the way it said in 1979.



The original (non-Applesoft) Apple ][ did not initialize BASIC
automatically.  It had to be cold started from the keyboard.


I've used the monitor to display ROM contents. The Monitor ROM, F800 and
up, matches pieces of code in the Reference Manual. The remaining ROMs
contain what looks like junk, and do not match Reference Manual listings.

 From the functioning monitor, and good readouts from monitor ROM, I
conclude that the ROM address and data paths work. That makes me think
that the junk data from the other ROMs is due to failure of the ROM
chips themselves.


Although this is possible, it is not a likely failure.


Can you suggest alternative explanation for the symptoms, or tests I
should do to confirm or reject the ROM hypothesis?

One of my friends, an electronics technician, suggested that some types
of ROM in use in the time period did tend to lose their data with time,
and it is a 27 year old computer. I don't know if that applies to the
ROM used in the Apple II.




Is there a source for replacement ROM chips?


The original set of 4 ROMs, Monitor and Integer BASIC, are a
little hard to find.  Best bet for the 3 Integer BASIC ROMs is
a "firmware card" with the Integer ROMs installed--they show up
on eBay from time to time.


Thanks, I'll keep my eyes open.




Although the computer has no practical use, it has very great
sentimental value as my first personal computer.


I hear you loud and clear, Patricia.  ;-)

-michael

NadaNet networking for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
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