Instructor: In this lesson,
we're going to talk about "Multi-channel Memory."
Now, multi-channel memory allows a system
to use two different memory modules at the same time
in tandem to increase the performance and throughput.
For example, if I'm using single-channel memory,
this means that I'm using one 64-bit data pathway
or data bus between the processor, the memory controller,
and the RAM modules.
But if I have two different modules and I operate them
in what's known as dual-channel mode,
I can then have two 64-bit pathways working together
giving me essentially a 128-bit pathway.
This interleaving actually gives you increased performance
that actually more than just doubling your speed.
I like to think about it this way.
When you're using interleaving,
let's say you had two horses and they're pulling a cart.
Now each horse might be able to pull 100 pounds by itself,
but working together, those two horses
can actually pull 250 pounds.
Now this is actually more than each one could do
by themselves or adding them together.
And that's really what happens
when we start doing interleaving.
This is the same idea
with the speed of access and interleaving.
Now, when we do this, the sum total of both
can actually access more
than either one could do individually.
So what kind of multi-channel setups might you find
out in the field?
Well, there's really four basic ones.
These are known as single-channel, dual-channel,
triple-channel, and quad-channel.
With single channel, you're using one memory module
on one bus.
So if you have a 64-bit data bus,
that means you're going to have 64-bits being sent
to and from the processor at every clock cycle.
If you're using dual channel,
this is going to require two memory modules
and two memory slots on the motherboard
that are working in tandem together
and interleaving themselves.
This takes those two 64-bit pathways and combines them
to give you essentially 128-bits of data
being sent per transfer every single clock cycle,
instead of only 64.
Now, in addition to this,
you might move up to triple-channel.
And with triple-channel,
you're going to use three memory modules and three slots
all in tandem with this interleaving notion
to give you up to 192-bits of data transfer
over that path to the 64-bit processor.
And finally, we have quad-channel.
Now with quad channel, we're going to take four memory modules
and four slots and have them all working in tandem
to give us 256-bits of data transfer
on each clock cycle to and from the processor
from our memory units.
Now, when you're configuring dual-channel, triple-channel,
or quad-channel,
it's important to consult your motherboards manual first.
This is because every motherboard is a little bit different
in how they set them up.
For instance, just because your motherboard
has four slots doesn't mean it supports quad-channel.
It may only support single-channel and dual-channel.
And you wouldn't know that unless you check your manual.
Generally, when you're looking at the slots
on your motherboard, they're going to be labeled
as zero, one, two, three, and four, or A0, A1, B0, B1
if we're doing them in banks.
Again, it's important to check your documentation
on your motherboard to know which slots
to put your memory in, especially if you want to be operating
in something other than a single-channel configuration.
Another thing to keep in mind
when using multi-channel configurations
is that it is considered a best practice
to use the same model make speed and throughput of memory
in all of the slots that are going to be a part
of that same multi-channel working together.
For example, if you're going to have four slots
on your motherboard, and you're going to be operating
in dual-channel configuration,
and so you're going to use two of those slots together,
you want to make sure that the memory module
in both slots is the same size, such as eight gigabytes
or 16 gigabytes, and the same speed such as 16,000
or 32,000 megabytes per second, to ensure
that you're not going to have any compatibility issues
or errors pop up later on.
So when it comes to multichannel memory,
remember, you can have multiple modules working together
to give you faster speeds in addition to having
a higher overall amount of memory
that you can use for storage.
This is an important consideration to have.
And so if your motherboard does support multi-channel
and you are already going to be using multiple modules,
you might as well take advantage of the increased speed
that you can get by using multi-channel
as a configuration feature.