Re: Switching from Debian i386 to AMD64
On Wed 05 Jul 2017 at 11:34:20 (-0400), Gene Heskett wrote:
> On Wednesday 05 July 2017 07:58:26 Matthew Crews wrote:
>
> > >Now that I know that I'm 64 bit capable. Would I see any benefit in
> > >switching?
> >
> > I would switch to AMD64 if you are comfortable with reinstalling
> > Debian. You will see a performance increase, even on a minimally
> > spec'd system. (I'm not sure its possible to convert a live install
> > from 32-bit to 64-bit).
> >
> > Phoronix did some testing with Ubuntu 32-bit vs 64-bit, and even with
> > a low amount of ram, the performance difference was substantial. This
> > benefit *should* apply to Debian as well. This test was several years
> > ago, as well.
> >
> > http://www.phoronix.com/scan.php?page=article&item=ubuntu_x86_1304&num
> >=4
> >
> > As for software compatibility, even with AMD64 Debian installed, you
> > can still execute 32-bit code.
>
> For those applications doing realtime machine control, 32 bit is king
> with its reduced data storage (= time wasted) on the stack when doing a
> context switch. Even the PAE versions suffer, and where a 32 bit os can
> do that switch in 2 or 3 microseconds, PAE doubles that, and the 64 bit
> stuff lags by another 10 to 15 microseconds at a given clock speed. Not
> hugely important when driving servo motors, but when driving stepper
> motors with software step generation, that variable step timing messes
> with the motors, costing you 75% of the motors speed capability.
> So now, with 64 bit everywhere, we're being forced to use driver cards
> with fpga's doing the step generation in hardware. This raises the cost,
> but not bank breakingly so. $100 a machine perhaps.
About time too, Gene. I was avoiding all that fuss 15 years ago
by programming an MC1401 chip to do all the dirty work, It could
internally generate various smooth acceleration profiles etc too,
leaving me (and my 266MHz CPU) to concentrate on the application.
Cheers,
David.
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