"(e-mail address removed)" said in
The only thing I would add to the above is the fact that much PC133
memory is high density, and most PC100 is not. What this means is
although the faster speed may work in your computer, your computer may
not recognize the total size of the PC133 stick.
Higher density? What do you mean by that? The PC-100 and PC-133 that
I've gotten in the past were both DIMMs (chips on both sides of the
PCB). They usually look like
http://snipurl.com/5znr with the 8 chips
on the frontside (9 for ECC) and the controller chips on the backside.
The "density" (
http://snipurl.com/5zo3) remains the same for, say, a
256MB memory stick whether it is PC-100 or PC-133.
The chip count remains the same (8) so going higher density means going
to a larger size memory stick, like a 128MB stick is higher density than
a 64MB chip. Most motherboards (except really old ones) can handle
different density modules in each slot. Some older ones required that
you use the same density within a bank (i.e., within a pair of slots).
You have to check what the maximum module size that the motherboard can
handle in a slot. If it can handle modules up to 512MB and you put in a
1GB module then you only get 512MB total and have wasted half of the
module and your money. Also, for old motherboards, the density within a
bank might be required to be the same for both sticks; i.e., if a bank
is composed of 2 slots then the motherboard might require that the
density be the same for both modules in those paired slots. It depends
if a one or two slots comprise a bank. If a bank consisting of a slot
pair requires the same density then just match the stick size; i.e., if
slot 1 has a 128MB stick then put another 128MB stick in slot 2
regardless of which was PC-100 or PC-133. Best is to read the manual
for your motherboard to figure out what the manufacturer states are the
limits or restrictions for memory.
While density doesn't apply here when discussing PC-100 and PC-133, I
have seen some modules that have a different architecture; i.e., the
arrangement of chips is different so the distribution of them
contributing to the bit width differs than the standard 8-chip module.
You had to make sure within a bank to use the same architecture for both
modules. However, I haven't personally seen this for PC-100/133 DIMMs
(see
http://snipurl.com/5zoi for pictures of standard memory module
types) but I have seen it with SIMMs. Density goes up (for each chip on
the PCB) as the total capacity of the memory stick goes up because the
architecture remains the same (8 chips, 9 for ECC).
Crucial notes that some systems won't run with a mix of PC-100 and
PC-133 sticks (
http://snipurl.com/5zoc). The most likely reason is
probably due to SPD (serial presence detect) which reports to the
motherboard the stick's specs. Some motherboard will detect the specs
from the stick in the first slot and use those for all slots. So if you
were to put the PC-133 in the first slot then the motherboard might set
the clock rate to fast for the PC-100 in the other slot(s). Same goes
for CAS delay: if the first stick had a CAS delay of 2 (even if it was
PC-100) and the other slots had sticks with CAS 3 (even if PC-133) then
the motherboard would use a CAS of 2 nanoseconds reported by the first
stick which might be too fast for the other slower sticks. I'm not
quite sure how the new motherboards handle a mix of specs for multiple
sticks so I play it safe by putting the stick with the longest CAS and
slowest speed in the first used slot to ensure using the least common
denominator for specs (but I usually make sure all the sticks are
matched in specs so I don't have to worry about which stick goes in
which slot). Could be the newer motherboards now use the least common
denominator of the SPDs across all memory sticks; i.e., if there is a
mix of CAS-3 and CAS-2 then CAS-3 gets used, and a mix of PC-100 and
PC-133 will result in a 100MHz clock. The motherboard can't be running
each slot at a different bus speed and with different delays.
It is likely that your non-server motherboard uses unbuffered memory
(
http://snipurl.com/5zou and
http://snipurl.com/5zoy). Make sure you
match with what your motherboard supports AND with the type for the
existing memory sticks that will remain in your system. Because the
keying for the PCB is different, you can only use one type in all slots.
The PDF download for the Soyo manual at
http://snipurl.com/5zp7 doesn't
even mention buffered or unbuffered. The Crucial memory selector listed
unbuffered memory modules for this motherboard (I only looked at a
couple sizes but the motherboard's memory slots would all be keyed for
the same type of memory).
