AlphaStation 200 NVRAM Problem

[Robert Jarratt]

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Maciej W.
> Rozycki
> Sent: 26 April 2016 00:42
> To: General Discussion: On-Topic Posts <cctech at classiccmp.org>
> Subject: RE: AlphaStation 200 NVRAM Problem
> 
> On Mon, 25 Apr 2016, Robert Jarratt wrote:
> 
> > To help me work out why my program isn't working I went back to the
> > console command to try to write to the flashbus index register, I used
> > the following
> > command:
> >
> >      deposit -l pmem:100000000 94000000
> >
> > This should set up the flashbus register to write to the LEDs. Instead
> > I got a machine check and an "Illegal target address".
> 
>  Hmm, I wonder if:
> 
> >>>d -l -physical 100000000 94000000
> 
> would make a difference.  I guess not, but probably worth checking.


I suspect not, but will give it a go.

> 
> > Am I misunderstanding the technical manual? Are those addresses it
> > gives for the flashbus registers physical addresses?
> 
>  I'm sure they're physical (see Chapter 3 too).
> 
>  One possibility is SRM unmaps them when it takes over from SROM, for
> safety maybe -- so as not to let one corrupt flash by accident easily
(BTW, I do
> recommend write-protecting flash with its jumper for these experiments --
> with DROM not working correctly and hence no way to load SRM from a
> floppy you'd be doomed if flash broke too).  The symptoms should look like
> ones you've got, though of course plain poking at the wrong area would
look
> the same.


I will check for unmapping, but I get a machine check when I write code
running in OpenVMS that attempts to write to the same physical location.
This assumes my code is correct of course, which is what I was trying to
verify by using the console.

This makes me wonder if the problem is that the DROM is getting the same
errors. But I am not sure if that can be true because then the DROM would
not be able to write to the diagnostic LEDs either (and the SROM wouldn't be
able to load the DROM, presumably).


> 
>  You could check if flashbus is mapped by peeking at bank 8 memory
> controller registers and seeing if the contents provide the necessary
wiring
> (in particular if bit #0 aka `s8_Valid' in the 16-bit word at
> 0x180000b00 is 1).  These registers are listed in the same manual -- with
a
> further reference to the (rather fat) memory controller manual.  If not,
then
> you'd have to set them yourself.  There could be PALcode entry points to
> access flashbus too I suppose, although regrettably my Alpha-fu is not so
> deep as to know this offhand.


I need to understand more about the Alpha architecture to understand this,
but I will check. All I can say is that I did try to read the bank 8 base
address register and I did get a value, but I didn't undertand what it
meant. Will do some reading.


> 
>  NB all the address space from 0x100000000 through to 0x1ffffffff is
> uncacheable it would seem, so no need to be concerned about this part.
> 


Thanks

Rob