🚀 go-pugleaf

In article <5d5qdt$m3v@godzilla.zeta.org.au>, craig@zeta.org.au (Craig Dewick) writes:
>In <32F66272.2339@cngp.cng.com> Ian Crozier <icrozier@cngp.cng.com> writes:
>
>>My first byte is 72 on a Sparc20 and my Ethernet address starts
>>8:0, so I guess that in your case the 80 of hostid and 8:0 of the
>>ethernet address is just coincidence.

It's a coincidence, and even that only due to an abuse of form.  The "80"
at the start of the host ID and the "8:0" at the start of the Ethernet
address are actually two different numbers: 0x80 (8 bits) and 0x0800
(16 bits).

>>My last six characters are the same on both, so I guess that's
>>universal on Sun equipment.

No, this is only true for more recent systems.  I believe the cutover
started with the SPARCstation 20, but I'm not sure of that.  A few more
details may be found below.

>>Can anyone add more enlightenment?

I'll try.  Please note that the information I'm providing is not guesswork
or speculation.  I helped define the current Sun host ID specification.

>Yes. Sun ethernet adresses all start with '8:0:20'. As for the first byte 
>of the host ID, this is what's referred to as the machine type

This used to be true, for machines through the SPARCstation 20.  But for
every system currently built by Sun (okay, I'm not sure about the upcoming 
Starfire (Ultra Enterprise 10000) systems), it works as follows:

	If the high-order bit of the host ID is set, then the remaining
	31 bits comprise the serial number, and the high-order byte has
	no special meaning.  For all currently shipping systems, the
	serial number is the same as the low-order 24 bits of the Ethernet
	address.  The high-order 7 bits of the serial number will always
	be zero.

	If the high-order bit of the host ID is not set, then the high-order
	byte defines the machine type.  The low-order 24 bits comprise the
	serial number.  On older systems this really was a serial number;
	on more recent systems (possibly only the SPARCstation 20, although
	I'm not sure) it is the low-order 24 bits of the Ethernet address.

And has been pointed out numerous times before, there is no relationship
between the host ID, the "serial number" encoded in that host ID, and the
serial number in the bar code on the back of the box.

>Here's a list of machine types for machines that use an NVRAM to store 
>their ethernet address and serial number data (they're in hex remember):
>
>[snip]
>
>80 - seems to be just about everything else (perhaps not the Ultra's though)

Yes, even the Ultras.

>If you install an NVRAM programmed with an incorrect machine type you'll 
>see messages about this when your machine boots, but it should still work 
>fine.

On the whole this is not true.  There are certain sets of systems which
will happen to work (an IPC identified as an SS1 or 1+, for example), but
if there are any fundamental differences in things such as cache size or
MMU setup, the best you can hope for is that the system will run in a
crippled state.  In many cases it won't work at all.

	Regards,

	Glenn
-- 
Glenn Weinberg    Sun Microsystems Computer Company  glenn.weinberg@Eng.Sun.COM
Opinions expressed above should not be construed as representing any position,
official or unofficial, of SMCC or Sun Microsystems, Inc.