Experimental Physics and
Industrial Control System

Till Straumann <[email protected]> · Wed, 6 Jun 2018 17:51:22 -0700

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.

HTH
- 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 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