Re: Advice on VME processor cards for EPICS

[Andrew Johnson <anj@aps.anl.gov>]

TYLER, Paul wrote:

> So my major question and then a minor one.  Any suggestions on
> replacement VME processor cards with Operating System options?  Price
> is a consideration.  We also have a preference for cards that can run
> Linux and RTEMS.  Also is anyone running with Pentium based systems?

I have an alternative suggestion, although you'd be a bit out on a limb to 
begin with if you did this: you can run Linux on many of the Motorola 
MVME2xxx PowerPC CPU boards.  I did a port of Hard Hat Linux 2.0 for the 
really cheap MVME2100, but I think some of the standard distributions can 
run on things like the MVME5100.

The problem with this approach is that you won't be able to make much use 
of the existing EPICS drivers for VME cards, as they're all written for 
the vxWorks memory model (no protection).  If you're going to have to 
write all your own device supports anyway then it might not be too much 
extra work as you can access the VME hardware from user mode through one 
of the Linux Universe-2 drivers, although interrupts are one thing for 
which you probably can't avoid having to write a kernel driver.

It would be interesting to see if something like ucLinux (a version of 
Linux for CPUs that have no MMU) could be made to work on the MVME boards 
(giving direct visibility to the hardware from User code), but I don't 
think it's been ported to PowerPC and the architecture includes an MMU 
anyway, so it would be a slightly strange setup.

Overall I'd guess RTEMS on an MVME2100 is probably your cheapest solution, 
although I'm not sure whether an RTEMS port for the 2100 actually exists 
yet.  Given the price difference of the cards though doing that port might 
very well be worthwhile.

- Andrew
--
"Life is what happens while you're busy making other plans." - John Lennon