Experimental Physics and
Industrial Control System

Michael Davidsaver <[email protected]> · Wed, 6 Jun 2018 14:10:58 -0700

Hi Matt,

The MVME3100 is based on the MPC8540 processor.  This chip doesn't have an FPU.
Other boards do (eg. mvme270x, mvme6100, or mvme2500) and RTEMS supports this.

I can certainly confirm that lack of an FPU really hurts performance, even
something as (apparently) simple as integer to float.

Michael

On 06/06/2018 02:03 PM, Matt Rippa wrote:
> It appears we've compiled our mvme3100 bsp without FPU support.
> We're on the mvme3100 running EPICS 3.14.12.7 and RTEMS 4.10.2.
> 
> We're attempting to commission our astrometric kernel control system
> and we've run into trouble meeting some of our thread deadlines. What
> we've found is a transform routine that takes our mvme2700 ~200 us,
> takes the mvme3100 ~8 ms.  So not a surprise to see this with only "-msoft-float"?  
> 
> ...
> 2018-05-31-tcs.log:May 31 11:41:15  E) PORT: tcs_vme, MSG: Welcome to rtems-4.10.2(PowerPC/Generic (*no FPU*)/mvme3100) 
> 
> Is FPU support possible with RTEMS 4.10.2? If so, what would we need to do?
> It looks like there's a multilib on 4.11.2 https://docs.rtems.org/releases/rtems-docs-4.11.2/cpu-supplement/powerpc.html#multilibs(*Eg., see #13* )
> 
> Here's our bsp specs:
> 
> beatnik:
> -specs bsp_specs -qrtems -fasm -c -mcpu=7400 -D__ppc_generic -DUNIX -O2 -g -g -Wall
> (mvme2700) mvme-2307:
> -specs bsp_specs -qrtems -fasm -c -mcpu=604 -mmultiple -mstring -mstrict-align -meabi -DUNIX -O2 -g -g -Wall
> mvme-3100
> -specs bsp_specs -qrtems -fasm -c -mcpu=powerpc *-msoft-float* -D__ppc_generic -DUNIX -O2 -g -g -Wall
> 
> Thank you!
> -Matt
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System