On Thu, Dec 29, 2016 at 6:24 AM, Rick Murphy <r...@rickmurphy.net> wrote:
> You could verify by writing a simple toggle-in that does the skip to test: > 0200/ 6661 - skip on the flag > 0201/ 7402 - halt if it doesn't skip > 0202/ 6662 - clear the flag > 0203/ 6661 - did that clear it? > 0204/ 7402 - yes > 0205/ 7402 - no I single stepped through that section of FRTS and 6661 definitely skips. > The FRTS does the following: > LPTEST, LSF > IFNZRO LPTEST-415 <****ERROR.....Change Loader****> > JMP NOTLPT > LPTLCF, LCF /CLEAR FLAG > TAD I LPGET > SNA CLA /CHECK FOR SPURIOUS INTERRUPT > JMPDIS, JMP DISMIS /GO AWAY IF SO > > So, it's skipping, then clearing the flag. So, if there was real hardware, > this would only trigger once. > Try the above on a minimal system, then add boards until the problem comes > back. I did that last night, but it didn't go away, Duh! I think I figured it out. There IS an LPT interface. I have a 32kW memory that I build up many years ago and I included a printer port on it. I haven't used it in eons and I forgot it was even there. I will have to figure out how to disable it. I don't remember if it did interrupts or not. There is also a PIO interface for IDE disks on there. > -Rick -chuck