[fpc-devel] 64 Bit / 32 Bit

Jonas Maebe jonas.maebe at elis.ugent.be
Thu Oct 4 13:30:29 CEST 2007

On 04 Oct 2007, at 13:24, Michael Schnell wrote:

>> It's probably better to directly introduce a longdouble type with  
>> longdouble (128 bit) semantics on all platforms. I don't think  
>> that emulating the almost nowhere supported 80 bit type does much  
>> good.
> Is 128 bit supported by any hardware ?

Most hardware only directly supports up to 64 bit precision.

> 80 bit is and it's an IEEE standard format.

It's a fuzzy standard. The IEEE "double-extended precision" is only  
defined as ">= 79 bit", similarly to how "single-extended precision"  
is defined as ">= 43 bit".

> So I can't imagine why it is "nowhere supported"

Because the x86 is pretty much the only one to support it in  
hardware. Similarly, the m68k supported a 96 bit double-extended type  
which is supported (almost?) nowhere else, and it's just as IEEE  
standard as the x86's 80 bit floating point format. It just doesn't  
make sense to emulate such cpu-specific types on other platforms.


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