every computer needs RAM to function but did you know that pretty much all the
RAM we use these days uses some clever tricks to run much faster than it
otherwise would even older RAM like
this ddr3 i'm holding uses these techniques
in fact it's right in the name ddr stands for double data rate which means
just what it sounds like it means it can move data twice as quickly as single
data rate memory which hasn't been in our computers for very long the original
ddr actually came out way back in 2000
not to be confused with the other ddr which came out in 1998. unfortunately i
don't have a stick of the original ddr to show you but i can show you a bit
about how it works so this is an example of a simple clock
signal that your computer uses to keep components inside synced up
conventionally one piece of data is sent per cycle or for each one of these humps
but you see how each cycle has a rising and a falling edge well ddr sends data
on both the rising and the falling edges which works because your memory modules
can detect at what point the internal clock is in its cycle but hold on a
second this would only be double the data rate over a super old school
single data rate RAM so how are we getting generational improvements like
ddr2 3 and 4 which continue to increase
the data rate by a factor of two each time it turns out that there are
actually two clocks involved in what make ddr RAM work the external bus that
connects your RAM to the rest of the system and an internal memory clock for
ddr2 the internal clock was kept the same but the external bus clock was
doubled this means that the external bus can carry twice as much data per unit of
time to take advantage of this the internal memory array where the data is
actually stored doubles the number of bits sent at one time to the external
memory bus this process is also called prefetching and it's responsible for why
ddr2 is faster than ddr and why ddr3 is
faster than ddr2 the external bus's faster clock can then carry the extra
data and boom you've got faster memory advances in manufacturing that keeps
signal integrity high have allowed newer versions of ddr to operate at these
higher speeds without a hitch it should be noted however that ddr4 works
slightly differently in that memory arrays are divided into bank groups
which means that prefetches can be pulled from different parts of the RAM
at the same time leading to higher speeds than ddr3 boosting the external
clock is also part of how newer versions of ddr can run at faster clock speeds
while drawing less power because the
internal memory array runs at speeds slower than the external bus and sends
more prefetch data per cycle it keeps power requirements from getting too high
which when combined with smaller die sizes means new ddr generations don't
need as much voltage of course unlike
many other generational improvements one thing that newer versions of ddr do not
feature is backwards compatibility this is a stick of current gen ddr4 and
you'll notice that when i hold it up next to this stick of ddr3 that the
notches are in different places that means that these two sticks cannot be
used in the same motherboard it's made this way on purpose since the different
generations of ddr have different electrical and signaling requirements
that or it's just a plot to make all of us buy new memory every couple years
either way i'll cough up whatever they want as long as it has RGB big thanks to MSI
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