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SubjectFloating point exceptions: how to mask & set to zero w/ no error indication?
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Excuse my Unix & floating point ignorance please, but I'd like to
generate some form of compatability with Speak Free (see
ftp://ftp.fourmilab.ch/pub/kelvin/speakfree/unix/prior-releases/p/sf61a2.tar.gz
), the main author John Walker <kelvin@fourmilab.ch> said:

> If the original PARC LPC code (which remains in the program,
> as it is a standard VAT and RTP compression mode) is generating
> floating point errors, this indicates that your system is not
> masking floating point exceptions and handling them by default.
> The LPC code routinely generates floating underflows, which the
> FPU should set to zero with no error indication.

I take it this can be made a default by the kernel, or the user
program can ask for this somehow.

> If you're getting interrupts for this, your coprocessor support is
> enabling interrupts most systems mask.

The english got jumbled at the end, but I fear what he means is that
it's enabling uninterruptable (or unmaskable) interrupts -- which may
or may not kill performance of that driver (I don't know how many
floating point errors it generates per second -- I suppose this could
be counted). What I think he means is that there's some bit that needs
setting :).

How do I do that? If there is an interface that I need to interact
with in user programs, then I'll do that in Speak Free (& send patch);
else, can the kernel handle this by default?

Thanks a lot for assistance,
Bradley Allen <Ulmo@Q.Net>

P.S. That latest alpha of Speak Free is pretty good even at 14400bps
modem PPP connections, with the -lpc10 option on sfmike (remember not
to run everything with -d (debugging)). I just wish the full duplex
drivers for the SoundBlaster AWE32 on Linux/*nix were reality (there's
an experimental one for Windows already).

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