SUMMARY: Changing default boot drive on 4/330

From: Colin Johnson (
Date: Wed Jan 17 1996 - 14:13:18 CST


Thanks to the many responses, I asked:

> We've (!) got this aging 4/330, which as you should know is from
> before the days of OpenBoot. There are to identical drives inside
> however the one that was the boot drive has finally been retired, or
> rather I've installed the system onto the working drive.
> Now I've got the manual for the Boot PROM but to save a lot of agro
> (ie I really am not sure I understand it) does anyone _know_ the
> exact sequence to change the default boot-device to a different
> SCSI disk??

I've attached a few submitted methods for skinning said cat. Thanks to:

Kevin Martinez <>
jgotobed@LPL.Arizona.EDU (Joe Gotobed)
Patrick Nolan <pln@egret1.Stanford.EDU>
parks@xdiv.LANL.GOV (Parks Fields) (Mark S. Anderson) (Jerry Springer)
Torsten Metzner <>
Michael Wright ED23 <>

Kevin Martinez <> was first to reply with this:

>Become root through su or by logging in as root.
>The eeprom command will show you the current contents of the EEPROM.
>The eeprom bootdev command will show you ther current boot device.
>bash# eeprom bootdev
>The eeprom bootdev= command with an argument will change the boot device.
>remember to escape the ( and ) characters.
>bash# eeprom bootdev=sd\(0,0,0\)
>bash# eeprom bootdev
>This operation should be successful unless you have a bad NVRAM. My
>4/330s have recently all needed replacement of this device. It is easy to
>do and relatively inexpensive - $16 each.

I used the following table from Torsten Metzner <>
to get the device number.

>eeprom bootdev=sd\(0,NR,0)
>Value for NR:
> 0 0
> 1 1
> 8 2
> 9 3
> 10 4 Because NR is in Hex
> 18 6 Because NR is in Hex

Alternatively, you can actually do this at the EPROM level as suggested by (Jerry Springer):
>The first thing you should do is sit down with an ascii chart
>and figure out the hex equivalents of the device name you want to use.
>For instance if you want to boot from device sd(0,0,0) then five values
>you need are 73 (s) 64 (d) 0 (0) 0 (0) 0 (0) (of course single digit numbers are
>Then you need to put these in prom locations 19-1d (hex)
>This is accomplish by typing the command q followed by the hex address at the
>prom prompt.
>You would type q 19 and hit enter.
>It will display the current contents and allow you to modify it. Put in your
>new value and hit return. The next address should appear. Continue making
>changes untill all five values are entered.
>At this point you should be display the contents of hex location 1f (1d being
>the last value associated with the boot device. To exit prom edit mode you
>can either type a space followed by a carriage return or a . followed by a
>carriage return.
>It sounds worse than it is.

and also by parks@xdiv.LANL.GOV (Parks Fields)

>You want to go the the eeprom and set the boot device q18 must be a 12.
>q 19 = the first letter of the device
>q 1A = the second letter of the device
>q 1B = the controler
>q 1C = the device
>q 1D = the partition
>its acsii code
>expample you want to boot from sd1
>b sd(0,1,0)
> the > prompt type the following a space bar or l1-a will end the sequence.
>q 18 12

  Colin Johnson Direct +44 1483 204164
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            The only reason God built the world in seven days
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