[comp.unix.ultrix] Ultrix 4.0's Perception of Memory Size

dcr0@gte.com (Dave Robbins) (04/19/91)

I am running Ultrix 4.0 on a DECStation 3100 with 24MB of memory.  The PROM
code recognizes and tests 24MB of memory, but when Ultrix is booting up it
insists that there is only 12MB of memory.  Why?  /vmunix is configured to
expect 24MB ("physmem 24" in the config file).  Is there something more I
should do to tell Ultrix how much memory it has?  Is there something it looks
at in the hardware and there's not a doggone thing I can do about it?  This
is a fairly recent upgrade from 3.X, and if I remember correctly the earlier
version did indeed recognize all 24MB (but I'm not positive about that).
Did I waste my company's money on 12MB of memory?
-- 

Dave Robbins                    GTE Laboratories Incorporated
drobbins@gte.com                40 Sylvan Rd.
...!harvard!bunny!drobbins      Waltham, MA 02254

ajc@thendara.pa.dec.com (AJ Casamento) (04/20/91)

	Dave,

	  If your operating system is only reporting 12MB of the 24MB that
	you have loaded have you tried re-seating the memory SIMMS? One of
	the prototype DS3100 units that I used to have caused me a similar
	problem when I added memory (though I will admit that I did the
	installation myself). Although generically the fact that the console
	level is able to see all 24MB indicates that the memory is properly
	installed.

	  The only other time I've seen this is when somebody tries to mix
	1Mbit and 4Mbit DRAMs in the same system (unlikely in your case) as
	Ultrix does not currently support such mixtures.

	  I hope that this helps.

				Thanx,
				  AJ

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diamond@jit345.swstokyo.dec.com (Norman Diamond) (04/22/91)

In article <11029@bunny.GTE.COM> drobbins@gte.com writes:
>I am running Ultrix 4.0 on a DECStation 3100 with 24MB of memory.  The PROM
>code recognizes and tests 24MB of memory, but when Ultrix is booting up it
>insists that there is only 12MB of memory.  Why?  /vmunix is configured to
>expect 24MB ("physmem 24" in the config file).

Sounds like it might be something dumb (nothing personal; I've made the
same dumb mistake before) like forgetting to copy the recompiled vmunix
executable to /vmunix before rebooting.....
--
Norman Diamond       diamond@tkov50.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.

dcr0@speedy.gte.com (Dave Robbins) (04/22/91)

In article <11029@bunny.GTE.COM> I write:
>I am running Ultrix 4.0 on a DECStation 3100 with 24MB of memory.  The PROM
>code recognizes and tests 24MB of memory, but when Ultrix is booting up it
>insists that there is only 12MB of memory.  Why?

I received several good followups via mail and news, and ... following the
advice of more than one respondent, I dropped back into the PROM code and
ran the self-test.  All 24MB passed the self-test, but still /vmunix insisted
that there was only 12MB of memory.  Following one suggestion, I switched off
the machine, opened up the box, and shuffled the SIMMs in the second 12MB.
When I switched it back on again, the self-test still found 24MB of good memory
(at least I didn't kill any of the SIMMs in the process :-).  But ... when I
booted /vmunix this time, *it found 24MB of memory* -- imagine that!  So, I am
now happily running with the system actually thinking it can use all of the
memory that exists on the machine.

Many thanks to all of you who responded to my query.  Collectively, your
suggestions did the trick.

Of course, I might wonder:  what is it about the SIMMs that the self-test
sees them all but /vmunix sometimes doesn't?  Oh well, mine is not to reason
why.
-- 

Dave Robbins                    GTE Laboratories Incorporated
drobbins@gte.com                40 Sylvan Rd.
...!harvard!bunny!drobbins      Waltham, MA 02254