Mixing SIMMs & DIMMs

First, as far as I know, SIMMs and DIMMs have never been able
to coexist in any mobo. In addition most older mobos require that
DIMMs be installed with no blank sockets between them.
Additionally many boards required that DIMMs of different sizes
be installed in a particular order, usually the largest DIMM had to be
1st.


"Timothy Lister" wrote in message
...
I upgraded the RAM on my old MS5158 mobo(430TX chipset) a while
ago from
64MB(consisting of 2SIMMs of 16MB each occupying all the SIMM slots
& a
32MBDIMM in one of the three available DIMM slots). I'd purchased a
64MB
DIMM from Crucial, but found that although it registered when
installed on
its own or with the other DIMM in an adjacent slot, if I installed
it in
most other combos with the DIMM or in any combo with both the SIMMs
in
place, the mobo would register it as a 16MB stick!!
I eventually found that I had to dispense with the SIMMs, then
one
combo would give me the full 96MB( all other combos registering as
48MB!).
Why would a RAM module register as being 16MB when it's in fact
64MB? I
would have thought that it'd register the lot or none at all?
I'm just curious as to any suggestions as to why it would only
partly
register? Thanks for any suggestions that you may have!

There are also issues with density of the DIMMs
and their location on the mobo. As I recall, when I
looked at your manual, that there was a chart, a barely
comprehensible one at that, that gave locations for various
combinations of different density memory sticks. That may
be able to explain your location issues. Incidentally your
board is the first I've run across that will accept SIMMs and
DIMMs simultaneously.

"Timothy Lister" wrote in message
...
I thought that was the case as well, yet this configuration
resulted in
a total RAM of 48MB, with the new 64MB stick (in the first slot)
registering
as 16MB!! Putting the smaller 32MB stick in the first slot & the
bigger 64MB
in the second without anything in the SIMM slots (or the remaining
DIMM
slot3) is the only configuration that recognises the DIMMs for what
they
are!
Previous to this upgrade, I ran 64MB with 32MB DIMM in slot1 &
identical
16MB SIMMs in each of the two SIMM slots (I understand that they had
to be
installed in identical pairs, according to the manual downloaded
from MSI's
homepage)with no problems at all!
I've read through a number of forums & can only find references
to
sticks not registering at all due to mobo constraints, etc, but
havn't been
able to find reference to problems where DIMMs are only partly
registered!
The manual advises against using modules requiring different
voltages,
as I believe SIMMs & DIMMs do on my board, but goes on to provide
plenty of
info about population rules for mixing the two types! It's a very
old board,
lacking any AGP slots, etc!
It's not really a problem for me as I've achieved the upgrade
that I
wanted. As I'm learning about the hardware though, I'm just
intrigued as to
why my 8x64Mbit module would sometimes only be seen as 16MB!
I'm not looking for any definitive answer as obviously that
would
require detailed knowledge of my hardware, etc, rather I was just
hoping for
a feasible suggestion as to why this may have occurred! At the end
of the
day, I suppose that I'll never know as I'm unlikely to persevere
with such
an old board for much longer anyhow! Thanks for the memory pointers,
as it
all helps my education in these things!

"Timothy Lister" wrote in message ...

Previous to this upgrade, I ran 64MB with 32MB DIMM in slot1 &
identical
16MB SIMMs in each of the two SIMM slots (I understand that they had
to
be installed in identical pairs, according to the manual downloaded
from MSI's homepage)with no problems at all!

It's not a good idea to mix +5V SIMM with +3.3V DIMM because the
higher voltages of the SIMM signals will cause the protection in the
DIMM chips to activate, and this gradually wears out the protection
through excessive current and maybe excessive heating. Once the
protection is gone the memory cells are ruined in a hurry. The
exception is with motherboards based on SiS chip sets because they
keep the SIMMs and DIMMs separate, and Gigabyte used to boast of the
ability of their Socket 7 boards to use SIMMs and DIMMs together. If
a motherboard can boot even with only 1 SIMM and no other memory
installed, then it uses one of these SiS chip sets.

Some motherboards allow mixing of the two types of RAM and say so in the
motherboard manual. It is not common to allow this but they exist.

Your problem is that you are using new ram with chips that are of a higher
density. Old motherboards often can't use this ram. Even newer motherboard
can't handle some 256mb stick or 128 because of the denser chips. I have a
new 256 mb that will work only in my newer motherboard, it registers as 128
in the older ones.