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Re: UX400S: a decent machine

    Date: Mon, 22 Jan 90 09:12 CST
    From: dmitchell@backus.trc.amoco.com (Donald H. Mitchell)


    Just to confirm understanding: the Unix box containing the UX board is
    not responsible for any of this window stuff.  The Unix box hosting the
    display is responsible for running the genera program (and thus
    generating the FEP window).  This distinction is important to people
    thinking about putting a UX in a fileserver that they do not want to
    spend any CPU cycles hosting the board but want the client Unix box with
    the display to shoulder all the burden.

Unfortunately, this summary is not quite accurate.

There are three machines involved here:
	- The "embedding host"; the Sun in whose chassis the UX400S
	  board resides.
	- The "display host"; the Sun on whose console the Genera window
	  and FEP window are displayed (via X as described in previous
	- The UX400S.

The embedding host's computrons are used for the following:
	- Running the genera program to manage the cold load stream.
(This is very low burden, especially while Genera is running and the
FEP is idle.)
	- Network communications via the Sun's ethernet interface.
	- Disk I/O (for paging) via the UNIX file system.  (This is the
most noticeable task, but is exactly what fileservers are already doing
for diskless or dataless Suns.)

The computrons to "manage" the Genera console window can come from
either the display host or the embedding host, depending on how and
where the genera program is run.  (In fact, these computrons are
negligible, except for run lights.  See below.)  For instance, one can
run the genera program on the embedding host in such a way that it will
only do cold load management, and then run the genera program on the
display host to get a Genera console:

	emb-host% genera -cl-display display-host: -no-console
	display-host% genera ux400s

One can also run the genera program on the emb host so that it will
manage both the cold load window and the Genera console:

	emb-host% genera -cl-display display-host: -display display-host

The only real difference between the examples is that (in 8.0) in the
second example, the emb-host will burn some computrons updating the run
lights.  Updating the run lights can only be done by the genera program
running on the embedding host; it happens fairly frequently (else it
would be useless), and can therefore impose some load on the UNIX in