[fpc-pascal] Freepascal Floating Point Issue

[Sven Barth]

Am 25.08.2017 01:33 schrieb "Ralf Quint" <freedos.la at gmail.com>:
>
> On 8/24/2017 2:45 PM, Ched wrote:
> > And under "modern" Windows, the extended type, which is fully
> > supported by the FPU, is *degraded* to double. So, I can't do high
> > precision computation with fpc even if the native hardware permits
> > such computations. I'm glued to XP as the full capabilities of the FPU
> > were on the hands of programmers, years ago.
> It's not a problem of "modern" Windows, but a problem of any 64bit x86
> OS that in that "long" mode the FPU does NOT support the extended data
> type (80 bits, 10 bytes). In 32bit mode, the FPU is using the "old" x87
> FP unit on the chip, in 64bit mode, it is using the SSE FP unit, which
> doesn't have those 80 bit registers, it's 64 bit only (and several times
> faster).
> So that you can use that with your Windows XP version is likely due to
> the fact that this is a 32bit version, not XP Professional 64 (or
> Windows Server 2003 64 for that matter).
>
> There are apparently some ways to enable the FP calculation to use the
> x87 FPU and therefor the possibility of those 80 bit registers on Inter
> chips (so far), but for one, this runs significantly slower that the SSE
> FPU, and then this is apparently not supported by (all) AMD CPUs, so you
> are limiting yourself also on which systems your code can run...

Plase note that all non-Windows 64-bit systems have no problems with
enabling the FPU and even Windows needs to handle it due to 32-bit software
requiring it.
The only x86_64 OS we support that doesn't have Extended enabled (by
default) *is* Win64.

Regards,
Sven
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