Check 68040 is an application which checks for a problem that appears to exist on some 68040 processors (at this time I have not seen any which passed this test with the caches on, but I have not tried it on all revisions of the 68040). This problem affects certain debugging operations, but, as far as I know, should not affect normal computer applications.
All processors in the 68000 family have a tracing facility which debuggers such as TMON can use to single-step over instructions. Unfortunately, on some 68040s, this tracing facility is unreliable and can cause instructions to produce incorrect results (In the cases that I've seen, the processor appeared to skip an instruction in the middle of code). Since the problem occurs infrequently and (apparently) randomly, you are most likely to encounter it when doing repetitive tracing such as using the Monitor to step, trace, or gosub until an expression is true. The chances of encountering it at other times are slight, so, except for watchpoints, the Monitor should still be usable.
The application Check 68040 will tell you if your 68040 system has this problem. The problem may be dependent on cache settings, so if your system allows you to disable the processor's caches, you can disable them and run Check 68040 again.
DISCLAIMER: This program is experimental. Use it at your own risk. The problems in the 68040 chip have not been confirmed at this time. I am not aware of any alternative explanations of the behavior of the code that performs the chip test in this program, but it is possible that it is in error (you can look at it yourself; it has the label “68040 Checker”). The results of the program are not guaranteed in any way.
