Re: Testing memory in an ULTRA60

[Eduardo Horvath <eeh%NetBSD.org@localhost>]

On Sun, 24 Apr 2011, Matthias Scheler wrote:

> On Sat, Apr 23, 2011 at 06:14:08PM +0100, rjs%fdy2.demon.co.uk@localhost 
> wrote:
> > Do they look identical, same chips and same PCB layout for each module
> > ?
> 
> They looked identical on a quick glance. But I don't feel like dragging
> the U60 from under the desk and opening it. :-}
> 
> Anyway, according to Volker they must be identical because the machine
> would otherwise reject the bank.

That's not necessarily true.  Most versions of OBP will read the DIMM SPD 
information to come up with a common configuration and use that.  DRAM 
configuration is a complicated mess.  They may even all be the same size, 
but if even one of them has a different layout of banks it can restrict 
the use of the entire bank.  What you really want to do is dump the 
contents of all the SPD data from the DIMMs and compare them, but I don't 
know how to do that offhand without a debug OBP.  You might want to poke 
around in the Forth dictionary to see if there's some way to access that, 
but it's unlikely since it's usually only processed during the config 
phase.

Eduardo