At 06:23 AM 2/1/00 -0500, Jon Lindgren wrote:
>On Tue, 1 Feb 2000, Marcus Frey wrote:
>
>> > 2) RAM: according to the manual, the Decstation accept only
>> > ECC RAM; is there any way to use non-ecc SIMM ??
>> 
>> The DEC3000-300 accepts PS/2-SIMMs with parity only. You can use pairs of
>> 8MB or 32MB modules. The usual PS/2-SIMMs for PCs have no parity bit and
>> can't be used in the DEC3000. The memory check at startup recognizes
modules
>> without parity, but if you do a TEST MEM you will see the truth :-)
>> 
>> My DEC3000-300XL was not too picky about memory modules, single-sided 70ns
>> 8MB modules with parity ripped from an old 486-PC work perfectly. It even
>> accepted modules of different brands within one bank.
>
>I seem to remember someone pointing out to me that standard 32mb parity
>modules won't work; supposedly DEC had a resistor on the 32mb simms which
>allowed the 3000's to figure out which simms are 8 and which are 32...
>
>I've never tried it, though.  I think nmanisca@vt.edu had tried a standard
>32mb simm on his new 3000 without luck, so YMMV WTR simms, qed :-)

Right Jon, most 'standard' 32MB parity simms will be recognized as
8MB simms.  They will function perfectly as 8MB simms btw.

You can use 'standard' 8MB simms just find, but if you want 32MB 
simms in there you need to make sure that they implement the presence
detect bits.

As I understand it, there are 4 bits on each simm (I do not remember
what pins they correspond to) that are used to identify the simm's
speed and size.  Most 32MB simms do not implement these correctly, causes
it to look like an 8MB simm.

I have heard that it is possible to use drops of solder to convert a
non-recognized 32MB simms to a recognized 32MB simms but it is not trivial.

So beware if you plan to use 32MB simms.

Hope this helps.

Nick Maniscalco
nmanisca@vt.edu