Cpu ID under UNIX

[Guy Harris]

> The VAX hardware supports the ability of obtaining the CPU id.

I don't remember seeing this in the 750 or 730 CPU descriptions, but it may
be there.

> Under VMS its obtained by the call to LIB$GETSYI. Has anyone done this
> under UNIX.
> ...
> I'd like to see a standard system call in UNIX for doing this (provided
> hardware support, of course).

Sun threw out "sethostid" from 4.2 and changed "gethostid" to return the
host ID from the ID PROM.  The 4.2 manual says that this 32-bit identifier
is "intended to be unique among all UNIX systems in existence."  It also
says that it is normally the Internet address of the machine; this begs the
question of gateway machines which don't have something which can be called
*the* Internet address of the machine.  I don't think any 4.2 code uses this
number as the Internet address (all the code either does a "gethostname" and
a "gethostbyname", or looks at the address the host has *on a particular
interface*).  I suspect the only reason the Internet address is mentioned is
that it will be a 32-bit number which is guaranteed to be unique; of course,
if you're not on the Internet (or, at least, don't have a properly-assigned
Internet address), you're out of luck.

If all VAXes have a (32 bit) serial number register, this register's
contents (or the serial number part; it may contain hardware or microcode
rev levels and the like as well) could serve the same purpose on a VAX; just
rip out "sethostid" and change "gethostid" to get the CPU ID.

Of course, if not all VAX CPUs *have* a machine-readable CPU serial number,
the whole discussion is somewhat moot (I think it just contains rev levels,
plant IDs, and the like on other VAXes).

	Guy Harris