Shopping for most kinds
of computer hardware is easy. If you pay even basic attention to the industry
you're not going to have too much trouble following individual trends and
understanding the basic specifications you'll find on desktops, laptops, or
even components. But in your perusing the shelves at your local Best Buy or the
e-stocks of an online retailer like Newegg.com, you may have noticed one
unusual and even arcane-looking acronym come up time and time again: DDR3. What
is it? What does it mean? And what happened to DDR and DDR2?
At its most basic, DDR3
is the current standard for system memory, aka RAM or, to get more specific,
SDRAM. It's the fastest consumer RAM currently in widespread use, and the type
you're most often going to want to buy (today, at any rate) if you want to
upgrade your computer or if you're planning to buildone from scratch. DDR3 has
all but replaced the older DDR and DDR2 in the marketplace, which is why these
days DIMMs using those earlier technologies can be somewhat difficult to find
and expensive to purchase.
But what exactly does
the term "DDR3" mean? To understand that, you need to understand its
history.
SDRAM, or synchronous
dynamic random access memory, was developed in the early 1990s to solve a
problem that began cropping up as computers became more powerful. Traditional
DRAM used an asynchronous interface, which means it operated independently of
the processor—which was not ideal if the memory couldn't keep up with all of
the requests the processor made of it. SDRAM streamlined this process by
synchronizing the memory's responses to control inputs with the system bus,
allowing it to queue up one process while waiting for another. This way,
computers couldexecute tasks much more quickly than had previously been
possible, and was the memory standard in computer systems by the end of the
1990s.
It didn't take long
after the introduction of SDRAM for hardware developers and regular users to
determine that even this route had its limitations. The original SDRAM operated
via a single data rate (or SDR) interface that, in spite of the type's overall
advances compared with DRAM, could still only accept one command per clock
cycle. As computers were becoming more popular and more complicated, and thus
issuing more complex requests to the memory more frequently, this was slowing
down performance.
Around 2000, a new
interface method was developed. Called double data rate (or DDR), it let the
memory transfer data on both the rising and falling edges of the clock signal,
giving it the capability to move information nearly twice as quickly as with
regular SDR SDRAM. There was another side benefit to this change as well: It
meant memory could run at a lower clock rate (100-200MHz), using less energy
(2.5 volts), and achieve faster speeds (transfer rates of up to 400 MTps).
As technology
progressed and processors became still more powerful and demanding, DDR alone
became insufficient. It was followed, in 2003, by DDR2, which refined the idea
even further with an internal clock running at half the speed of the data bus;
this meant it was about twice as fast as the original DDR (200-533MHz, with
transfer rates up to 1,066MTps), but again used less power (1.8 volts).
Naturally, DDR3 was next out of the gate (it debuted around 2007), with its
internal clock cut in half again, its speed about twice that of DDR2
(400-1,066MHz, for a maximum transfer rate of 2,133MTps), and power usage
reduced even more over its predecessor (to 1.5 volts).
(You may have already
surmised the next logical step in memory technology. Indeed, DDR4 is already in
development, and will probably begin appearing in consumer products around
2014, with wider adoption to follow gradually.It's expected to offer transfer rates
of up to 4,266MTps, with voltage ranging from 1.05 to 1.2 volts.)
What's the down side to
this constant improvement of memory? Unfortunately, you can't benefit from most
of these advances without significantly upgrading—if not outright
replacing—your current hardware: A DIMM that uses one kind of DDR interface
will not work in a motherboard designed for another. Each type of memory is
electrically incompatible with the others, starting with the number of pins on
a chip (DDR desktop-style DIMMs have 184, and DDR2 and DDR3 each have 240), and
DIMMs using each are keyed (or notched) differently so they can't even fit in
the wrong kind of socket. It's therefore crucial that your existing hardware
and the memory you want to add are of the same DDR type.
The good news is that
because DDR3 is so prevalent today, you probably won't need to worry too much
about this until DDR4 starts gaining ground in a couple of years. If your
computer uses the DDR2 standard, there are definitely compatible chips out
there, but expect to pay more and get less: A quick search on Newegg revealed
an 8GB kit of high-speed G.SKILL DDR3 RAM available for $84.99; the same amount
of slower DDR2 cost $149.99. And if your computer is stuck on the original DDR,
you may want to consider a full-system upgrade. (A mere 2GB of that, also from
G.SKILL and also slower, is $59.99.)
When you're purchasing
memory, it's also best to verify that its speed matches that of your
motherboard; otherwise, performance bottlenecks may result. At least this information
is easy to determine from the memory's specs: If you have a motherboard that
supports the DDR3 1333 standard (the "1333" references the memory's
transfer rate, in MTps, not the actual speed of the memory, as is commonly
assumed), you'll be fine as long as the memory uses that same designation. If
the memory is slower (meaning, it has a lower DDR3 number) you won't be
accessing your computer's full potential; if it's higher, you risk the
processor not being able to keep up with it.
Neither, of course, is
ideal: You'll get the best results when all of your computer's components are
in harmony. Given the work and inspiration that went into DDR3, built on the
platform of the types of memory that came before it, wouldn't it be a shame to
not take advantage of the speed increases it offers if they're available to
you?
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