correction Re: Sun 4/110 FPU

[Ruth Milner, Systems Manager x2746]

In v7n114 I reported that:

>The Sun 4 (all models) FPU is not an option, but an integral part of the
>CPU that does all floating-point operations.

My apologies; this is wrong. On Sun 4/110's the FPU *is* an option. On Sun
4/2x0's it is not (or at least, it isn't listed as such on my price list).

I can think of two ways to determine whether you have an FPU. The first
one is a visual check of the hardware, i.e. whether or not the chips are
there. The second, if you need to be able to check from a program, is to
check the EF bit in the %psr register. This reports whether the FPU is
enabled/disabled (enabled but not present should = disabled, but you may
need to attempt a simple fp operation and trap the fp_disabled exception).
I have reason to believe there will be better utilities in the near
future, analogous to the Sun 3 fpaversion program, but don't know when
these will be generally available. See Ch. 3 of the SPARC Architecture
manual for details.

Thanks to Sam Finn and Bruce Barnett for pointing this out to me. I hope
my mistake did not cause any problems for anyone.

Ruth Milner
Systems Manager
University of Toronto Physics

sysruth at helios.physics.utoronto.ca