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3675 Memory

    Date: Fri, 13 Oct 89 12:30 EST
    From: Len%AIP1%TSD%atc.bendix.com@RELAY.CS.NET
 
    How much memory can a 3675 have?  I tried using 1-2 MW (in physical slot
    0) and 4-1 MW boards (in physical slots 1, 2, 3, and 4).  The 1cards0 (3
    per board) were assigned to slots 15 down to slot 4) and the last 4
    1cards0 (1 and 1/3 boards) were assigned to slot 29 with the notation "no
    room in memory space."  As it stands now the herald shows 4864K words of
    physical memory.

I.e. 4 3/4 MW.  Are you sure that one of the virtual "cards" was assigned to
slot 4?  The Fep should have been able to detect the board in physical slot 4,
and avoid assigning other cards to that slot.  (You also didn't mention where
your IO board was, but that's not really relevant.)
 
    Is this the best I can do with this hardware?
 
    Len Moskowitz
						       Allied-Signal Aerospace
    moskowitz@bendix.com (CSnet)                       Test Systems Division
    moskowitz%bendix.com@relay.cs.net (ARPAnet)        Mail code 4/8
    arpa!relay.cs.net!bendix.com!moskowitz (uucp)      Teterboro, NJ 07608

Yes.  The 3600 series was designed at a time when 1/2 MW per physical slot was
a lot!  Larger memory boards are made to appear as if they occupy 4 slots:
the one that they physically occupy, and three "logical" slots (usually
assigned at Hello time by the Fep's Initialize Hardware Tables command).  The
2-MW card fills each of the 4 slots to its 1/2 MW capacity, but the 1-MW card
only offers 1/4 MW per slot, thus wasting 1 MW of physical address space per
1-MW board.

While the 3675 has a physical address capacity of 8 MW (16 slots), the IO
board takes up 1/2 MW, leaving you a max of 7 1/2 MW.  This maximum can be
reached with 3 2-MW boards and 3 1/2-MW cards (I set up such a system for Bill
Gosper when he held the record for most digits of pi).  It cannot be reached
at all using 1-MW cards.

You may wish to swap your 1-MW cards for 2-MW or even 1/2 MW cards, if you
wish to use all of the 6 MW that you have paid for.  Presumably you could swap
these with other machines on your site, or perhaps other SLUG members.  I
don't know whether we have a memory upgrade plan, but you might check with
your sales rep -- it doesn't make sense to pay for capacity you can't use.
 
 -- Chuck Fry
    Symbolics Software Support