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Subject: Re: MVME3100 FPU Support on RTEMS 4.10.2
From: Michael Davidsaver <mdavidsaver@ospreydcs.com>
To: Matt Rippa <mrippa@gemini.edu>, Talk EPICS Tech <tech-talk@aps.anl.gov>, Till Straumann <strauman@slac.stanford.edu>, "rtems-users@rtems.org" <users@rtems.org>
Date: 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
> 

Replies:
Re: MVME3100 FPU Support on RTEMS 4.10.2 Matt Rippa
Re: MVME3100 FPU Support on RTEMS 4.10.2 Till Straumann
References:
MVME3100 FPU Support on RTEMS 4.10.2 Matt Rippa

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