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Old 10 October 2018, 00:05   #1

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A2000/Blizzard060 NMI exception

Today I got a strange bug report regarding my game Trap Runner. At completely random, non-reproducible points, the system invokes exception vector 31, which is a level 7 interrupt (NMI)!

The attached screen shot shows the game's internal debugger, which catches the exception.

I am pretty sure that nothing on a standard Amiga board could cause an NMI. Maybe the Blizzard 060 does? Has anybody experienced that before? What can be the reason for it? And why does it cause such an exception randomly?
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Old 10 October 2018, 00:42   #2
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I seem to remember we were getting Level 7's or some other unwanted interrupt, randomly triggered on A2000 on our "The Fall" demo

Just found the thread about it:

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Old 10 October 2018, 12:32   #3

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Thanks for the confirmation. So I will just do an "rte" an ignore it.

But it's interresting that the problem was observed on a 030 board as well. So it is more related to the A2000 itself than to the expansion boards in use?
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Old 12 October 2018, 15:13   #4
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May be noise on the interrupt lines. Does demos like state of the art (trackload version, not whdload) also crash at random?

I had this problem with my home brew accelerator for the A500, and the solution was to add 510R pullup resistors on the 3 IPL lines (the ones on the mainboard are 4,7K) to reduce the noise sensitivity.

Everything was fine when in workbench, but when running demos like sota without proper handling of this interrupt, I got random crashes before applying the fix.
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