Just a note regarding installing RAM on old mainboard.

I've installed two 8MB EDO 72pin SIMM to replace 1 4MB FP SIMM on a HP
Vectra 486sx  desktop which have two 72pin slots.
Switched it on for a few secs. It won't boot. Switched it off and those RAMs
are extremely warm. I replaced it back with it's 4MB FP SIMM. Well, the
170MB Quantum hardisk had kaput.
Then, adding a piece of 4MB FP SIMM to the current RAM works making the
system running at 8MB RAM without any memory problem.

Never have such in-compatible issue that will permanently wreck the HD
before.

Luckily there'snt any important data inside the fatal hardisk though we have
to replace the hardisk for free.

Another bad day in Tech Support.

Best Regards,
Hial Noobt
Tech Department
-----Original Message-----
From: Tom Turak <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, April 28, 1998 1:06 AM
Subject: Re: [PCBUILD] PCBuild Memory types revisited.


>Your system stands a very good chance of supporting parity ram as
>non-parity when the BOIS selection is disabled.  I frequently installed
>30 pin parity ram mixed with 72 pin non-parity in 486's and had no
>problems when I disabled the BIOS parrity selection.  I don't know what
>you mean by staggered.  Do you have 30 pin simm slots?  Are they
>empty?  If you only have 72 pin slots you can probably install any
>combination of single sided and double sided simms.  Singles are
>usually 4 and 16, double 8 and 32. If you have 30 pin simms you
>probably have limited options with 8 and 32 meg simms since the
>bank numbers between the simm slots overlap.  This usually means
>a jumper has to be moved to assign bank zero to 30 pin or 72 pin ram,
>since a double sided 72 pin simm occupy one slot but uses to banks,
>( 0 and 1) and 4 30 pin simms make up on bank (usually).
>
>So the short answer turns out to be buy non-parity 16 meg and put it in a
>currently occupied slot, removing one of the installed four meg simms.
>The long answer is there really are not that many permutations to choose
>from and even without the manual you should be able by trial and error to
>find a way to install a 16 meg non-parity simm and get all the ram
>recognized.
>tom turak
>[log in to unmask]
>
>David Abbe wrote:
>> i have a 486 that was pieced together from spare parts lying around.  it
>> was given to me with no documentation.
>> It initially had 4 meg of memory, then another 4 meg was added.  The
>> chips are different looking, one is staggered one is not.  I still am
>> unsure how to tell if it is parity or non.  Looking on the chips
themselves
>> i see that it is 72 pin, and on one of them there are 16 (chips) and the
other 12.
>> I had thought that parity would have an odd number of chips on the memory
>> module, so now that makes these non-parity, my bios has a selection for
>> parity error checking, though it is disabled....so what do you all think?
>>
>> David A. Abbe
>> [log in to unmask]