Re: Testing Memory

["Michael J. Mahon" <mjmahon@aol.com>]

Robert C. wrote:
> I was wondering, is there a way of testing the apple's memory similar to the 
> way older PC's used to test memory on startup? I have an Apple ][+ with the 
> Microsoft 16K Memory Card and tried to check the memory above  48K by 
> running a simple peek routine from 49152 to 65536:
>
> 10 FOR X = 49152 TO 65536 : PRINT X;" - ";: PEEK (X) : NEXT X
>
> Unfortunately the computer froze immediately upon executing the program. 
> Checking the LED's on the memory card shows that the memory card had 
> switched to bank 1 before the error occured.

The program starts PEEKing at $C000, and all of the $Cxxx region
is dedicated to I/O and softswitches, which affect *everything*
on the Apple II.  Don't ever randomly PEEK or POKE in this area.
Start your program at 53248 ($D000).  BTW, stop at 65535 ($FFFF).

Doing this will read out the contents of 3/4ths of the memory
card.  Getting to the other 1/4th requires using a reference
to the bank switch location for the card, which maps the
current content of $D000..$DFFF out and the content of the
other 4KB into that space.

This doesn't really test memory, it only reads addresses, and
every address will return *some* value, whether memory is
connected to it or not.

There are memory test programs for the Apple II, but, in most
cases, just running some programs correctly provides confidence
in the memory.  For example, run an Integer BASIC program after
booting the DOS 3.3 System Master diskette.  That will load
Integer Basic into the memory card, then use it when you run
an Integer program.  If that works, your memory card is very
likely fine.

Or boot a version 1.x ProDOS disk and do some disk operations.
ProDOS runs in the memory card.

Maybe someone here has a reference to a good memory test for
the Apple ][+...

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

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