Fellas,
I could use a little help troubleshooting a backup Zip
GSX card that I bought used installed in a ROM 3 IIgs.
The card appears to work fine with _one_ exception --
When it is installed I cannot enter the Desk Manager
(Desk Accessories/CDA Menu) using the command-control-
escape keyboard sequence.
As you know, when that key sequence is entered,
(provided interrupts are not disabled) the ADB controller
sends an interrupt that is identified and then the Desk
Manager routine is initiated.
For some reason, the CPU on the Zip GSX is either not
receiving the interrupt, is ignoring it, or is not able
to access the Desk Manager vector.
Here's what I've tried:
1. Remove Zip GSX and re-install original 65C816 - Desk
Manager IS accessible. (So, the computer and keyboard are
functioning fine).
2. Re-install Zip GSX and re-seat Zip GSX cable and ensure
all pins are inserted correctly - Desk Manager is NOT accessible.
3. Enter the monitor and run short program to clear the
interrupt disable flag (CLI - 58) - Desk Manager is still
NOT accessible.
4. Ensured that the S1 (Control Panel Disable) Jumper is not
jumpered on the ROM 3 motherboard - Desk Manager is NOT accessible.
<BTW, this jumper may just disable control panel access, not the CDA menu>.
So, what's left - bad CPU, bad cable, broken trace? Other than this
issue, everything else seems fine with the Zip GSX. I'm stumped.
Has anybody here experienced this before or perhaps can shed some
light on what is happening?
Thanks.
Hugh Hood