🚀 go-pugleaf

On 15 Apr 1997, Dipl.-Chem. Clauswitz Kai-Uwe W. wrote:

> : when I have an SS2 with dead prom (no hostid, no
> : ethernet adress), can I just take a prom
> : out of an IPC or IPX and put it into the SS2 to 
> : get it running again ?
> : Will one of them work, or will I have to buy a new prom ?
>
> Sorry, I mixed something up.
> Of course I am not speaking about a prom,
> I mean the NVRAM.
> But besides this mistake- I would like to know if I can put 
> this one from an IPC or IPX to an SS2

You can definitely do this since both machine use the same type of NVRAM
(the SGS/Thomson M48T02).

The only consideration you need to make is that by installing the NVRAM
from a different machine, some of the values stored in the device will be
different from your original NVRAM.

The NVRAM stores three important variables - the machine type, as well as
it's ethernet address and serial number - and it also maintains the
current time/date by virtue of the built-in real time clock as well as
storing all the other things that the 'printenv' monitor command (and the
'eeprom' SunOS command) prints out. 

Because you're thinking about installing a NVRAM from something other than
an SS2 into your SS2 board, the machine type value will be different, and
as a result the checksum of the data in the first 15 bytes of the NVRAM's
storage space will be wrong so when your SS2 starts up it will complain
that the 'IDPROM' checksum is invalid (IDPROM is a historical name - see
below for an explanation). SS2's are machine type 0x55 (in hex), while
IPC's are 0x52 and IPX's are 0x57. 

There shouldn't be any need to worry about the ethernet address and serial
number. However, you can change the machine type value and recalculate the
checksum once you install the IPC/IPX's NVRAM in your SS2 by typing these
two commands at the 'ok' monitor prompt when the machine isn't running
SunOS:

55 1 mkp			(puts 0x55 into location 0x1 of the NVRAM)

0 f 0 do i idprom@ xor loop f mkp	(recalculates and stores the checksum)

Then if you type 'reset' at the 'ok' monitor prompt the machine will
restart and the NVRAM will be correctly set up as though it's always been
on your SS2 board. 

On the subject of IDPROM/NVRAM/etc., IDPROM is the historical name for
where the data stored in the NVRAM was kept in older machines (from the
early Sun-4 VME-based series back), because in earlier machines there was
a seperate IDPROM device that contained the machine type, ethernet address
and serial number, and an EEPROM for all the other data that's stored in
the NVRAM.

NVRAM's didn't start featuring until the 3/80 and 4/300 appeared (except a
4/300 uses the NVRAM only for the real time clock feature - they still had
seperate IDPROM's, etc.). Most of the Sun-3/3x series machines (except the
3/80) used a combination EEPROM's for the 'non-proprietry' settings, and
IDPROM's for the three important settings (the 3/60 is an example of
this). 

Regards,

Craig.

--
            Craig Dewick. Send email to 'cdewick@lios.apana.org.au'
   Point a web browser at 'http://lios.apana.org.au/~cdewick/sun_ark.html' to
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