[U-Boot-Users] AMCC PPC440EPx/sequoia stability question...

[Niklaus Giger]

Hi Dave

Dave Littell wrote:
> Hi all,
> 
> I'm working on an AMCC PPC440EPx-based platform that's similar to the
> Sequoia.  The board runs pretty well, but occasionally takes exceptions
> both in U-Boot and while running Linux.  The exceptions vary from
> Illegal Instructions to FP Unavailable to FP Unimplemented to ITLB and
> DTLB Errors, to DSI, etc., which made us believe there's a problem with
> SDRAM.  Sometimes there are simple hard lockups from which even the JTAG
> can't regain control.  However, the SDRAM physical/electrical and DDR
> Controller configurations have been investigated in detail (and some
> corrections made) with no resulting improvement in the exception behavior.
> 
> We see problems primarily at 667 MHz but have noted some issues at 533
> MHz as well.  Some boards seem particularly susceptible to this while
> others rarely (if ever) exhibit the problem.
> 
> At this point all possibilities are on the table and I'm looking for any
> input from anyone with experience (good, bad, or whatever) with this
> processor and/or designs similar to the Sequoia.
> 
We at netstal.com have here a new PPC440EPx based board called HCU5,
which runs well u-boot and vxWorks 6.4. Last August I had also linux
running which compiled on a NFS root its own kernel for a weekend.

Our HW is stable (running at 667 MHz) and we never had exceptions, which we
could not explain after looking around for its case.

We had (and still have) problems getting our SW (about  1 M LOC) correctly,
as the PPC440 has a lot of internal concurrency. We had a case were two
lines of C-Code which read some external HW-register were read in the
wrong order the loop was running twice or more times. Therefore we had
to look very carefully at how external devices were accessed and are using
memory barrier like in16/out16 a lot.

I have also seen JTAG lockups but could never figure out why.

Best regards

Niklaus