405EX Rev D mis-identification?

Lee Nipper lee.nipper at gmail.com
Fri Jul 9 04:54:49 EST 2010

On Thu, Jul 8, 2010 at 13:24, Josh Boyer <jwboyer at linux.vnet.ibm.com> wrote:
> On Thu, Jul 08, 2010 at 11:01:11AM -0500, Lee Nipper wrote:
>>On Thu, Jul 8, 2010 at 10:06, Marc Chidester <marcchidester at gmail.com> wrote:
>>> It looks like the Rev D version of the 405EX chip without security
>>> will be identified as a 405EXr, based on the values in the cpu_specs
>>> table.  For 405EX/405EXr the pvr_mask is  0xffff0004 with the
>>> pvr_value's as 0x12910004 and 0x12910000 respectively. I see that the
>>> Rev D PVR value for the 405EX without security is 0x12911473, which
>>> would mask out to the EXr value.
>>> Is there an algorithm update needed or am I missing something?
>>With 405EX Rev D, we have noticed that we must reset our board
>>one time after the initial powerup to make the PVR read correctly.
>>See this post:
> That is very very weird.  Have you seen that behavior on multiple Rev D CPUs
> or just one board or?

Multiple Rev D CPUs.  In fact, ALL of the samples we obtained behave this way.

> The PVR value should never change, so if you have odd behavior I wonder if the
> are silicon bugs in that revision.  Did you happen to ask AMCC about it?

Yes, I did.
AMCC suggested doing an early one-time s/w reset to make the PVR read
"correctly" afterwards.
Since we only support one specific 405EX variety, we could do that.

However, on a generic u-boot, there is no way to know if a "correct"
PVR is read,
so that approach is not a solution.

I'm wondering if our power on reset circuitry is not entirely correct,
and it showed up with the Rev D part.  I received no comments on my
original post
from other users of the 405EX, so I'm thinking it is a possible explanation.

Does anyone have a board with a 405EX Rev D ?
If so, does the PVR value match your processor chip after power up ?


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