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From: dbfunk@ICAEN.UIOWA.EDU (David B Funk)
Newsgroups: comp.sys.apollo
Subject: Re: 2500 memory: banks of 4?
Message-ID: <9002160959.AA00183@icaen.uiowa.edu>
Date: 16 Feb 90 09:46:34 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: Iowa Computer Aided Engineering Network, University of Iowa
Lines: 21

In posting <1990Feb14.101624.5666@metro.ucc.su.oz.au> Jim Richardson asks:

> Am I right in assuming that memory can only be added to a DN2500 in multiples
> of 4 SIMMS, that is, in multiples of 4 megabytes in the case of 1MB x 9
> SIMMS?  This is not mentioned in the "Domain 2500 Series Owner's Guide".
> However, the memory sizing output at boot time suggests that memory is being
> interleaved, with each of the four bytes in a longword coming from a
> different SIMM.  

  You guessed right Jim. The DN2500 needs memory in banks of 4 SIMMs.
This is because the bus between the memory & CPU is 32 bits wide to
keep the 68030 working at maximum speed. To get 32 bit wide memory you
need 4 bytes (4 SIMMs) per "whack". BTW this is also true in the Apple
Macintosh '020' & '030' machines. So the next step up from 4 Mbytes
is 8 Mbytes, 6 Mbytes is not an option. 
  For what it's worth, we run all our machines at a minimum of 8 Mbytes,
if you are going to do a bunch of "X" stuff, 12 Mbytes or more is
reccomended. Memory for the DN2500 really isn't very expensive because
they use the standard SIMMs. We've seen lots of sources for under $100 US.

Dave Funk