>in the FPEmulator module in RISC OS. If I'm right about that, presumably
>you'd need to install the fpem module in linux as usual, but the
>instructions which *are* in the silicon wouldn't generate traps and would
>be executed by the FPU?
It's not quite that simple. Yes, there are some instructions that the FPA
will never claim and the emulator will always get hold of, and those will just
work. The more tricky case is that under some circumstances I think the FPA
can claim and start to execute an instruction but then decide that it's too
complicated and punt to software to finish things up. This avoids the need to
dedicate silicon to handle all the corner cases of IEEE arithmetic. I don't
have the FPA datasheet to hand right now but I suspect operations involving
denormals probably fall into this category. The FPA support code needs to
know how to extract the information about bounced instructions from the status
word and finish things up. NWFPE certainly can't do this; I have no idea
whether the Linux version of the Acron emulator can.
p.
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