Re: [hatari-devel] FPU update

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your FPU test utility is good for testing for faulty chips, but is not exactly what we need for debugging the emulator. For every failing calculation i'd need to know the input operands and the result as it is and as it should be.
Would it be hard to modify your test program to serve that purpose? Or would it create too much data?
Theoretically i'd only need to test through all kinds of operands once (normal in range, denormal, zero, infinity (all +/-), nan and snan) and for some functions produce some special conditions (underflow, overflow). For the dyadic operations we'd need to test all combinations (normal + normal, normal + denormal, normal + zero ... denormal + zero, denormal + infitiniy ...).

Well, the longer i think about it, the more test cases come to my mind. One would certainly have to think a while to not miss an important test case.
At the moment i'm a little bit clueless on how to debug this. Simply following the data sheet (did that for the 68030 MMU) seems to be not good enough.


Yes I'm aware of this problem (diagnosing the cause) - but I didn't really want to do anything about it unless/until somebody raised a reason for it. I wrote it mainly because two of my programs were flaking out on some Falcons, and it turned out to be faulty FPUs.

I think it wouldn't be too hard to record all of the hashes, instead of just the final hash on each test - and stop on the first error. It doesn't necessarily generate too much data. However all it would do is halt near the fault - you'd still need to debug the instruction before the fault.

I can look at this when I get half an hour free.


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