MVME3100 FPU Support on RTEMS 4.10.2

Till Straumann strauman at
Thu Jun 7 00:51:22 UTC 2018

You could try to build with the APU support - then you get 
(single-precision only)
FP hardware support; it should work with normal context switching since 
the APU
shares the registers with the integer processor.

- Till

On 06/06/2018 02:10 PM, Michael Davidsaver wrote:
> 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 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*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

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