IBM 5160 oddball fault

[jwsmobile]

On 4/23/2015 9:20 AM, tony duell wrote:
> Yes, the cursor is generated by the 6845 on the CGA card.
Since the messages start out skewed to the right, I'd consider that 
there is a stuck bit in the data written to whatever 6845 location 
controls that.  If you can probe the bus and the data is okay most 
places, it may be noisy or corrupted to the slots.  Obviously a lot of 
the memory has to work for the bios to pass and run, so that is 
suggesting some problems getting data to the interface slots, though 
most of that is working or the display card would have failed as well.

Fault may be on the card data path as well, since so much other I/O is 
working fine.

thanks
jim