• Subject: Re: Have you read this?
  • From: leif@xxxxxxxxxxxxx
  • Date: Thu, 13 Jan 2000 07:43:37 -0600

Chuck,

You are missing the point:
1) The CPU has one of the most powerful FPUs around
2) The use of this FPU can be disabled in software by setting
a bit in the MSR (Machine State Register).
3) This 'disable' bit is set (at least on the low-end models)

So, the customer is paying for hardware that he has,
but cannot use it. An interesting issue is to what
models this apply. Only low-end, or all, or what?

BTW, the FPU can be enabled again in software...


> OK from reading the book "Inside the AS/400" by Frank Soltis (EVERYONE that
is
> interested in the AS/400 SHOULD read this book !!!), page 43-44, etc.
Muskie
> (A30) DID have FPU... So the 530 and 53S had it...
>
> Chuck
>
> leif@attglobal.net wrote:
>
> > > except that on some (all?) AS/400 models, the PowerPC floating point
> > > unit is disabled while running OS/400. So the calculations would run
> > > very slowly with emulated floating point operations.
> > > ---------------
> > > I find it a little difficult to believe that Rochester would design
what
> > they
> > > call "IBM's fastest floating point processor" for the old Muskie chip
sets
> > and
> > > then turn the thing off in all of those 530 and 53S machines.  Maybe
the
> > FPU's
> > > are turned off in low-end machines - that would be about par for the
way
> > IBM
> > > screws us over to create their bloody "price points" - but in all
models?
> > That
> > > doesn't seem reasonable.
> >
> > I have actually only confirmed this on low-end modes. I don't know about
> > the high-end (that why the 'all' had a ? next to it). I was hoping from
some
> > input from IBM lurkers on this.
> >
> > About the fast FPU, don't forget that it is also used on AIX.


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