AlphaStation 200 NVRAM Problem
Maciej W. Rozycki
macro at linux-mips.org
Mon Apr 25 18:42:11 CDT 2016
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
> 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.
> 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.
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.
NB all the address space from 0x100000000 through to 0x1ffffffff is
uncacheable it would seem, so no need to be concerned about this part.
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