Every component in your computer is important, complex, and has
more specifications than most folks are familiar with. Your RAM, or
Random Access Memory, is no exception to this. Generally, people
know that more RAM is better, but that's not the extent of it. It's
also not always accurate. Let's take a look at what you need to
know about choosing the right RAM for your PC.
If you're looking to upgrade the RAM in your current computer,
check out our article on identifying the kind of RAM you have so you
know what you're upgrading from.
Physical form factor
Did you know that the RAM in a desktop computer is going to be
different from the RAM found in a laptop? RAM modules will be found
as DIMM, which stands for dual in-line memory module. There are a
few different kinds of DIMM out in the market:
- UDIMM tends to be the most common type of RAM
module in the PC market, with the U standing for Unbuffered and/or
Unregistered. Generally, if RAM is listed as just being DIMM then
it's mostly likely to be UDIMM.
- SO-DIMM is the second-most common type of RAM,
as it's what you'll need for laptops. The SO means small outline,
basically saying that it's DIMM, but smaller. SO-DIMM can be
Unbuffered as well, much like above, and should be what you expect
to find for laptop RAM.
- MicroDIMM is like the above, but even smaller
than SO-DIMM. These types of RAM modules are far less common than
both of the above, but specific laptops or other smaller computing
devices may make use of them.
Modern RAM comes with different numbered DDR identifiers. For
better or worse, this has nothing to do with Dance Dance
Revolution. In RAM, DDR stands for Double Data Rate, with the
appended number (as in DDR4) indicating the generation of this
double data rate standard. Early computer RAM was typically
referred to as just DRAM, which stands for Dynamic Random Access
Memory. Most RAM is still effectively DRAM, just with better
circuit designs that enable memory to work more quickly and with
higher capacity. First, they added a clock signal interface so the
DRAM could sync up with other parts of the system, becoming known
as SDRAM. Then DDR was developed to double the amount of data
bandwidth available to the rest of the machines and you, its
From there came DDR2, then DDR3, and now most current devices
utilize DDR4 RAM. DDR5 does exist as a memory standard, and you may
find it mentioned in graphics cards, but DDR5 RAM modules aren't
quite ready for the market at the time of writing this article.
Whatever the case, though, your motherboard and CPU are going to be
the major determining factors on what kind of DDR RAM you need for
your PC, so know those specifications before choosing your RAM.
This is the part many people are familiar with: More RAM is
good, less RAM is bad. RAM capacity is the major specification
folks are looking for when purchasing. Generally, having 8GB of RAM
will provide a better computing experience than 4GB of RAM. Video
games will include RAM capacity in their recommended system
requirements. Various software will have their own minimum
requirements for available memory. This is all capacity.
You cannot just purchase as much RAM as possible, however. A
32-bit process and operating system could only make use of up to
4GB of memory, so the additional RAM on such a system effectively
goes to waste. Most modern systems are 64-bit, which can
theoretically handle up to 4 petabytes of memory, albeit most
modern PC CPUs tend to be capped at anywhere between 32GB and 256GB
of memory. As mentioned above, you'll want to refer to your CPU and
motherboard specifications to determine what RAM capacity your
system can handle—then following the edict of more is better aim
for the higher end of that spec.
This is the aspect of RAM that gets a bit complex. There are two
main factors behind what makes RAM considered fast: frequency and
First is the RAM's frequency, which is far too commonly referred
to as the speed. When looking at RAM products, you might find it
listed as DDR4-3200 or DDR4 2666 MHz. Those four-digit numbers are
the frequency of the RAM. Your memory is constantly doing reading
and writing cycles with your currently loaded data, and that
frequency is referring to how many times per second the memory is
going through that cycle. DDR4-3200 is referring to a 3200MHz
frequency cycle, which translates to about 3.2 billion read/write
cycles per second. So, generally speaking, a higher frequency is
better, but note that some CPUs and motherboards may not support
some frequencies effectively, and may require additional research
if you're looking to maximize your performance. Additionally, the
price for high-frequency RAM tends to ramp up very quickly.
Then there's timing, also known as Column Access Strobe latency
or CAS latency, which is a measurement of the delay between your
RAM modules receiving a command from the CPU and the RAM actually
executing that command. CAS latency is typically listed as a series
of numbers, such as 18-22-22-42, which is actually referring to a
series of timing values beyond just CAS latency. Typically, the
timing order is CAS Latency – Row Address to Column Address Delay –
Row Precharge Time – Row Active Time. Basically, lower numbers are
better. There is much more depth to go into here, but generally
speaking, differences in timing aren't going to make a huge impact
on your experience with modern auto-detect settings and memory
controllers on your motherboard and CPU.
If you're intrigued by the idea of overclocking your RAM, but
intimidated by the tricky manual process, you may want to look for
something called XMP support. You can read more about XMP in our article on how to enable XMP.
Think of memory channels as the roads between the CPU and RAM.
With only one road, there are only so many vehicles that can be
moving on it at once. Once the road is too busy, it becomes a clog
for those trying to get between those two points. Same goes for the
memory channels on your motherboard—a super-fast CPU and
high-powered RAM on a single channel can lead to that channel
becoming the chokepoint for your PC's performance. Most CPUs can
support two or four memory channels, and their compatible
motherboards tend to accommodate that with their available RAM
slots. In order to use multiple channels, you'll need more than one
RAM stick. In the instance where you have an incredible CPU and
outstanding RAM, it's typically better to use a Dual Channel 16GB
RAM kit, which is two 8GB RAM sticks with matching performance, as
opposed to a single stick of 16GB RAM. Though, the downside here is
that if you only have two RAM slots, then upgrading your RAM
capacity would mean replacing the RAM entirely, as opposed to just
adding another stick of RAM if you only had the single 16GB
Additionally, when it comes to having RAM on matching channels,
it's best to use RAM that has matching frequency and timing
performance. RAM working together on matching channels will need to
be in sync with each other. If their frequency and timing are out
of sync, the RAM scales back performance in order to get in sync.
Thus, it's best practice to get multi-channel kits for better
There are a handful of other RAM specifications that can be
helpful to know.
- ECC: Error Checking and Correction. ECC is a
potential RAM feature that inserts a step into the RAM module that
allows it to check and ensure the data it's handling is correct and
does not have any errors. ECC is an incredible solution for
reducing data/memory errors, but it also slows things down. Most
consumer RAM does not include ECC, but if you're working with a
heavy-computation scientific system, you may want to consider ECC
on your RAM.
- Registered/unregistered or
buffered/unbuffered: This was loosely mentioned above in
the section about the physical form factors. Registered and
Buffered are interchangeable terms here. Conventional consumer RAM
is going to be unregistered. Registered RAM is typically going to
be found including the above ECC features, as it's going to be a
feature that's more important for servers or other systems using an
incredibly large amount of RAM. Registered RAM helps carry some of
the load that would normally fall to the memory controller with
unregistered RAM, allowing the motherboard to support larger
quantities of RAM.
- Voltage: For most modern PCs, you probably
don't need to worry about voltage too much. It's a specification to
help gauge the amount of power the RAM needs to function, and is an
important specification for overclockers and those building very
particular systems that have very tight power requirements.
- Heat spreader: Like any hard-working part of
your PC, RAM does need cooling. For most systems, the typical case
cooling is enough for the RAM modules. For high-performance RAM,
you'll typically find it includes a heat spreader on the RAM stick
to aid in cooling capabilities. Heat spreader is effectively
another term for a heatsink.
- Height: This is a physical measurement of the
RAM stick, noting how tall it is. The vast majority of computers
don't need to be concerned about normal RAM height, but if you're
working on a small form-factor PC, then you may need to double
check the height profile of your RAM, as it can potentially be the
tallest piece of your tiny build.
Both form and function are important! RAM has been getting more
and more attention from its manufacturers to better support the
overall look of your rig. Many high-performance RAM kits,
especially those targeted towards gamers, tend to include sleek
looking heat spreaders and even multi-colored LEDs so you can
really build with something that shines.
To summarize, picking the right RAM kit for your PC is going to
be a matter of matching up the DIMM physical form factor, the DDR
type, and the amount (in GB) of RAM capacity you're looking for.
Additionally, considering the memory's frequency, timings, and
channels can help you get the most RAM performance for your budget.
Whatever you do, though, please don't try to download more RAM.