- [Instructor] Let's talk about some additional RAM features
and I wanna get into multichannel RAM and also ECC.
If you remember, in the previous video,
we talked about the connection between the RAM and the CPU,
and we said that we'll normally have a 64-bits connection,
64-bit bus, which means
that it can transmit eight bytes of data per cycle.
This is the original single channel RAM,
one 64-bit address bus or data channel.
However, what if we were to add additional banks of RAM?
Well, we could add more if we wanted to.
For example, if we added a second bank of RAM,
we would then have an additional 64-bit bus.
This would be known as dual channel
and in a dual channel setup,
the RAM works together and you then
have 128 bits altogether.
So now we're actually sending 16 bytes of data per cycle.
And you could go beyond this if you wanted to.
We could take that RAM and add some more.
If we add a third one, it would be known
as triple channel RAM.
We'd have three channels of RAM altogether,
and then it would be a 192-bit bus.
And on many computers today, you'll have a fourth channel.
So now we have connectivity here.
We have connectivity here, and they all work together.
All these 64-bit buses.
This would be known as quad channel.
And in a quad channel setup,
it comes to 256 bit, which is 32 bytes
of data simultaneously.
So the more channels you use,
if your motherboard can support it,
the more data you can send per second.
Now, in the previous video,
we said that we were using DDR4-2133.
That was the standard.
The name of the PC module was PC4-17000
or 17066, depending on where you buy the module.
But another type of feature
that you might see in RAM is called ECC.
ECC stands for Error Correction Code.
ECC in RAM can detect and correct errors.
Real-time applications might use ECC RAM.
You might see Error Correction Code RAM in servers
and high-power workstations.
And if you're purchasing the RAM,
you would see the difference in the name.
Instead of PC4-17000, in might be called PC4-17000E
and the E meaning Error Correction Code.
When you're using ECC, additional information needs
to be stored and more resources
are used in general on the RAM module.
This RAM is the slowest
and the most expensive of the RAM types out there.
For example, for every 128 bits of data that are stored,
DDR will store an additional eight bits
of data for the Error Correction Code.
If ECC is enabled, whenever the data is read,
the actual data and the ECC data
are read together by the RAM module
and by the memory controller on the CPU.
And so, newer versions of DDR
like DDR4 and DDR5 can repair single bit errors
on any data bits right away.
So that's really important for things like servers.
So make sure that you know
and understand multibank technologies like single channel,
dual channel, and quad channel,
and also understand ECC or Error Correction Code in RAM.