I found this a while ago.

>I found a method to reconstruct the hostid and ethernet address from
>the printed string on the NVRAM label.
>
>The old style labels have a barcode in that looks like code 39 and a
>four character string
>that uses the digits 0..9 and the letters A..Z . So the code 'FAXY' for
>example  is a number of  base 36. To reconstruct the hostid you have to 
>go to the openboot monitor or use a standalone FORTH.
>
>hex 24 base ! <string on label> EZ0G - hex .
>this returns the hostid. This worked for the three SLC and the one ELC
>NVRAM I had access to.
>Note that EZ0G is also a number of base 36. Its hexadecimal equivalent
>is AA8C0 . 
>
>Given the hostid you can reconstruct the last three digits of the
>ethernet address
><hostid> 27b00 + .
>On the ELC I found an offset of 77b00. As I only had one ELC to test I
>cannot tell if that offset can be used on all ELCs. 
>
>have fun
>-- 
>Dipl.-Inform. Peter Heitzer, phone +49 941 943 4850, fax +49 941 943 4857
>mail Peter.Heitzer@rz.uni-regensburg.de

>! -----Original Message-----
>! From: der Mouse [mailto:mouse@Rodents.Montreal.QC.CA]
>! Sent: Monday, September 03, 2001 1:00 AM
>! To: port-sparc@netbsd.org
>! Subject: old NVRAMs
>! 
>! 
>! I've got eight old 48T02 NVRAM chips whose batteries ahve run down.
>! I'd like to reconstruct the MAC address and hostid values 
>! corresponding
>! to them; all but one of them still has its barcode sticker 
>! (and I don't
>! expect to get anything useful for the one that's lost its sticker :-).
>! 
>! Mark Henderson's NVRAM FAQ says that Sun can reconstruct this 
>! given the
>! barcode (or, possibly, the four-character code also prinetd on the
>! sticker), but does not say how.  Is that algorithm known, or partially
>! known?  If not, I'll volunteer to collect data points to try 
>! to work it
>! out, if people with still-good NVRAMs will send their barcode and/or
>! four-character codes to me with the Ethernet address and hostid that
>! correspond.  (I've got only three live samples in my own collection,
>! not really enough to tell much from.)  I'll also be looking at mine to
>! see if there is an obvious correspondence between barcodes and
>! four-character codes.
>! 
>! The newer sort, the 48T08 sort, don't need this, since the last three
>! octets of the MAC address are identical to the low three bytes of the
>! hostid, and are printed under the barcode.  It's just the old sort I'm
>! interested in here.
>! 
>! Any information appreciated.
>! 
>! /~\ The ASCII				der Mouse
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>
>

Michael Thompson
E-Mail: M_Thompson@IDS.net