I need some help with my Apple III. Apple III disks don't start, only a very few work actually.
Strangely the Emulations of Apple II work, The Confidence Program works, and Atomic Defense works, but none of the other disks.
The Machine is futher in working order, with the keyboard diconnected the RAM looks to be OK.
The Confidence Program gives a Machine Status:
Memory Map good for 128K, although it's a 256K machine and has 256K installed.
Disk drives all checked and the Interrupt System all checked as well.
So something is not working with the memory...
Than on the memory test of the confidence program it does show the 256K and all 7 banks and the extension bar.
It passes the Zpage/Alt Stack Page test
and the RAM test stops with the following message:
RAM: BNK 83, ADR 20XX, EXP 20, GOT 22
I have swapped RAM around on the RAM board and it did change the expected and got message sometimes.
I have gotten EXP DD, GOT FD and EXP and EXP 22, GOT 23
So I haven´t been able to identify a bad RAM chip.
So my guess is that some of the logic that drives the RAM is faulty. That´s why it sees only the 128K. (shouldn´t SOS run on those 128K?)
Does anybody have a suggestion to identity the chip that is causing this behaviour.
Thanks (and Merry Christamas)