UNIX on Revision 5 VAX 11/750 CPU's

[Mike Williams]

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Our DEC field service engineer wants to update our 750 to revision 5. This
means updating the cpu module L0005 to L0008. What this means is that some
of the microcode can now be in RAM. The ideas is that modifications and patches
can be  loaded separately from disk after (or during) system start up. As far
as I can tell this modification should cause no trouble unless we have some
patches to install in the micro code. It seems that DEC want to do things this
way so that they can stop burning new PROMS for every change they want to make.
(Bit like the 780). 

All sounds very sensible and no doubt well supported in VMS. BUT what about 
UNIX? I can't get any information except that when this is first installed, it 
should make no difference since there will be hardly any patches to load. I
would however like to be able to install micro code patches later. Does anyone
know:

1 How is the RAM micro code loaded in VMS? Has anyone done anything about this
  in UNIX? How does ULTRIX (DEC UNIX) deal with this? My own thoughts are that
  the easiest way to do this loading in UNIX is to introduce a new system call.
  Loading micro code hardly seems to merit a special device and a driver! A
  small program in /etc/rc should suffice.

2 In what format will the patches be available? Will I just be able to copy
  the relevant patch file from a VMS machine?
  
3 Does anyone have a rev 5 750 CPU working under UNIX?

Mike Williams

{decvax,phillabs}!mcvax!enea!erix!mike