Re: gEDA-user: pcb crooked traces

[Gabriel Paubert <paubert@xxxxxxx>]

On Fri, Oct 08, 2010 at 11:14:04PM +0100, Peter Clifton wrote:
> On Fri, 2010-10-08 at 15:42 -0400, DJ Delorie wrote:
> > > Any idea of the loss of performance given that virtually all PCs 
> > > these days are actually 64 bit machines?
> > 
> > My dual-core 3.2GHz machine supports 64-bit, but I installed a 32-bit
> > OS for compatibility.  So, 64-bit math is a performance hit for me.
> 
> I'm not certain that is true.. or are you compiling with CFLAGS for a
> non 64-bit CPU? I thought the 32/64 bit OS issue was mostly to do with
> address pointers, rather than aritmetic.
> 
> I was fairly sure one could execute 64bit native CPU arithmetic
> instructions under a 32-bit OS, just that the executable would not be
> portable to machines which didn't support those instructions.

Not on the 64 bit version of x86 for integer computations. The most 
significant half of the 64 bit integer registers are not accessible 
at all in 32 bit mode.

On other architectures, I think it works (for PPC I'm sure, Sparc and MIPS
I believe so), but we are in an x86 monoculture these days. ARM does
not (yet) have a 64 bit version AFAIK.

	Gabriel


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