Subject: DECstation 5000/200 facts (was: PMAX HW trouble)
To: Matthew Patton <>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: port-pmax
Date: 12/02/1996 00:24:45
Matthew Patton writes:

[newly purchased DS500/200 doesn't boot Ultrix]

For reference:

>1. What's the rationale for memory slots?

There are at least two densities of memory cards for the 5000/200s
(and 5000/240s): 8Meg and 32Meg, IIRC. 

The hardware attempts to map memory as one contiguous chunk, rather
than leaving holes in low-memory configurations, as, for example,
Sparcstations dp.

The hardware has a writable register that controls the memory address
decoding.  At boot, the PROM pokes around in low memory to size the
memory cards (it writes a pattern and looks for the same pattern
aliased at other addresses.)  You have to have the first memory slot
populated, or this test fails.

Therefore, if you mix memory densities, you _must_ put the
higher-density cards in the lower-numbered slots.

Ultrix has never supported mixed memory-module sizes.  The hardware
supports it (I added it to the Stanford V-kernel).  Supporting this on
NetBSD is a SMOP (MACHINE_NONCONTIG, if anyone's interested.)

>2. I've got revision 5.6 of the ROM's, anyway to get a newer version?  

that's pretty recent. The ROM is much mor functional than the 3100s,
but the syntax is completely different. NetBSD has a sparse manpage;
try "cnfg" and "help" and "help" and "test", and "test N", for the
slots returned by "cnfg".

If "cnfg"  shows you disks, ethernet, and memory, and  the machine
passes self-test, it's probably fine.

>4. Is there a architecture difference between the 2000/3100's and the 
>5000 that makes my boot disk worthless?

Not an architectural difference, per se. But the 3100 kernel probably
doesn't include support for the 5000/200's internal bus or devices;
3100s are low-memory machines by definition and the only hardware in
common is a DEC custom serial chip, mouse and keyboard. You probaby
have an Ultrix kernel configured only for 3100s, so it won't boot. 
That suggests  it may not licensed for your 5000/200 either.

Contact whoever you bought the machine from and arrange a license
transfer, and get suitable media from them.

Or install NetBSD :).