Re: Defective RAM on Apple IIgs

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

Bryan Parkoff wrote:
> Folks,
>
>     I have experienced when I tried to copy files from DOS 3.3 to ProDOS 
> using Copy II Plus 9.1.  I compared both files on source and target.  I have 
> discovered that both are not identical.  I did notice garbage data from 
> sector to sector.  I assure to be defective RAM built-in on motherboard of 
> Apple IIgs (256KB).  I did diagnose using Ctrl-Open Apple-Closed 
> Apple-Reset, but it shows, "System Good".  It does not make sense.  It 
> should have scanned bank $0 through $3 to detect corrupted data in RAM.
>     I have tested another Apple IIgs motherboard.  It is working fine when 
> files are copied using Copy II Plus 9.1.  Maybe, I will need another 
> software to test defective RAM.  If it determines errors in RAM. there 
> should be a way to replace RAM chips on motherboard, but they are all 
> soldered.  Any suggestions?

There is no problem.

The differences you observe are a result of DOS storing the load
address and length of the file as the first four bytes, while in
ProDOS these values are stored in the directory.  This will shift
the contents of all sectors by 4 bytes, making them all "unequal".

-michael

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