- [Instructor] Random Access Memory,
or RAM is the workspace for the CPU.
The type of memory that we install
is known as dynamic RAM or DRAM.
DRAM is volatile meaning it does not store
its contents after a refresh, or a restart.
To keep the data after a computer restart
we need to use a hard drive,
or other long-term storage medium.
The sticks of RAM in the figure are called DIMMs,
or dual in-line memory modules.
In these videos, we'll concentrate on DIMMs
as they are the majority of the RAM that serves the CPU.
Now, the great thing about DRAM like this
is that the CPU has equal access
to all of the contents, and it can grab
any piece of information it wants at any time.
It does not have to do it sequentially.
Even if you have 32 gigabytes,
or 64, or 128 gigabytes of RAM the quantity doesn't matter.
It's like having this super enormous giant work bench
for projects, but also the ability to work
at any part of that work bench at any time immediately.
The problem with the CPU and RAM
is that they have sort of a closed relationship.
To enable that immediate transfer of data
between the DRAM sticks and the CPU
we need what we call the memory controller.
In today's computers, the memory controller
is actually integrated into the CPU itself.
The memory controller is the go between,
or liaison, if you will, for the CPU and the RAM.
It's responsible for storing data
to RAM and locating and fetching data from RAM.
It does this by use of the address bus,
which is the circuitry that connects
the CPU to the DRAM slots.
Your CPU's memory controller and therefore,
the CPU itself and your motherboard especially
must all be compatible with the RAM you want to use.
So know it, the CPU's memory controller
is in charge of storing data to RAM.
Now, let's get to the fun stuff, diagrams.
This diagram kind of puts it all together
for a computer system that you might be working with.
And this is basically what we call the chipset diagram.
On the upper right, we have our DRAM.
In this case it's DDR4, double data rate 4 memory
that runs at 2133 megahertz.
The DDR4 memory connects to our core i7 CPU
that we have here by way of the address bus.
Data flow between the RAM and the CPU
is governed by the memory controller,
which is part of the CPU.
Next, the CPU then connects out to the PCI Express bus
on the left, and to the chipset
by way of the direct media interface, or DMI bus.
The chipset then connects out to all secondary devices
and interfaces so you have connections out for audio,
the minor PCI Express slots, SATA, the USB ports,
the integrated network connection,
the firmware, the BIOS/UFI and so on.
So your chipset takes care
of all those secondary connections,
and it has a main connection to the CPU via the DMI,
or direct media interface bus.
And, again, that CPU has the connectivity directly out
to our video card, our PCI Express 3.0 or higher connections
and out to the memory directly via the address bus.
So remember that the sticks of DRAM
that we install are DIMMs, dual in-line memory modules,
and that DDR, or double data rate, is the type
of memory that we usually make use of,
which we'll speak more about in an upcoming video.