Re: fpu emulation

[Erik Dalen <erik@jpl.nu> writes:]

>I've been having a lot of problems getting my computers to work lately.
>The problem on some of them was probably because they were 486sx'es
>(without fpu). So I'm wondering how difficult task would it be to make an
>fpu emulation for VSTa? port the linux/BSD one?

The interesting part is how to do it in a "microkernel" sort of way. It'd
no doubt be easy enough to pull the FPU emulation from a monolithic kernel,
and paste it into the VSTa kernel. But... ick. You'd have to review its
design carefully anyway to handle the preemptive, SMP, and multi-threaded
issues. But even then, why bloat a kernel which has avoided bloat for so
long?

So instead, the question is how to attach it to the FPU-using process's
address space, and intercept math faults? In the latest release, the raw
event handling system calls of VSTa have been wrapped in an event registry.
POSIX signal emulation uses that, and it seems like a nice place for FPU
emulation to attach, too. But to have this automatically present means that
each process (at least each using floating point) has to "arm" this handler.
A clever way of doing this without an impact on integer-only programs would
be nice.

I've always got about this far in my thinking, and then I look at how few SX
chips are left in the world. :->

Andy Valencia
Received on Wed Sep 6 06:49:19 2000