On Wed, Aug 09, 2000 at 06:32:13AM -0400, Jon Lindgren wrote:
> On 9 Aug 2000, Matthias Scheler wrote:
> 
> > 	Hello,
> > 
> > from a quick look a DEC 3000 uses normal PS/2 SIMMs with parity. Does
> > anybody know the exact requirements? I would like to put more than
> > 64MB in a DEC 3000 but prices for "original" DEC 3000 memory modules
> > are still ridiculously high.
> 
> From what I understand, anything larger than 8MB will give you a problem
> if it's not the DEC memory (or equiv).  The difference is a small one -
> some of the lines on the SIMM are a bit nonstandard (I believe they're
> tied to ground with a resistor or such...), and that prevents "normal" 36
> bit SIMMs greater than 8MB being detected as such.  They still function,
> IIRC, but are only detected as 8MB.

From what I can tell it is standard.  But it is a standard that most simm
manufacturers do not implement.  There are four bits called the presence
detect bits (am I right?)  These give the computer a guess as to the simm's
size and speed (60 vs 70ns, 8MB vs 32MB etc).

> Nick <nmanisca@vt.edu> had experienced this a while ago when he threw some
> 16 or 32MB SIMMs into his 3000/300x; he manged to dig up some info on
> it.  Another explanation (found at random) is at:

These systems (the 3000/300s) will take either 8MB or 32MB simms.  If the
32MB simms do not propperly implent the presence detect bits then they
will be used as 8MB simms.  Some non-DEC simms DO implement these bits
correctly.  A friend of mine bought a pair of 32MB simms from a regular
PC memory supplier and he got lucky.  You could always take your
chances at try out some 32MB simms first.

Nick Maniscalco