a question about RAM

[kidlat017]

my one setup currently has 4x4gb ddr3 1333. 4 slots ram motherboard.

 

someone wants to buy one of the ram, and i still have another 2gb stick ddr3 1333. am I really only losing 2gb of ram if I continue the sale or is there something else that is going on?

[Pixelfie]

I recommend staying with the 12gb instead, mixing RAM can cause instabilities.

[kidlat017]

12gb? don't you mean 16? (4x4=16)?

[Eigenvektor]

3 minutes ago, kidlat017 said:

12gb? don't you mean 16? (4x4=16)?

Yeah 16 is correct. You'd go down to 14, but your RAM would (at least partially) stop working in dual channel, which would halve your bandwidth.

[kidlat017]

17 minutes ago, Eigenvektor said:

Yeah 16 is correct. You'd go down to 14, but your RAM would (at least partially) stop working in dual channel, which would halve your bandwidth.

half bandwidth? you mean I'm essentially only enjoying 8gb (2gbx4) if I did sell one of my 4gb stick?

[Eigenvektor]

2 hours ago, kidlat017 said:

half bandwidth? you mean I'm essentially only enjoying 8gb (2gbx4) if I did sell one of my 4gb stick?

No. If you have two (or four) identical RAM sticks, they run in dual channel mode. If your RAM sticks are not identical, then they fall back to single channel mode, which has half the bandwidth of dual channel mode. Meaning it'll get slower, but you'll still have 14 GB RAM.

 

(~edit: There's also quad channel, but consumer boards typically don't have that, so two or four sticks makes no difference)

[kidlat017]

1 hour ago, Eigenvektor said:

No. If you have two (or four) identical RAM sticks, they run in dual channel mode. If your RAM sticks are not identical, then they fall back to single channel mode, which has halve the bandwidth of dual channel mode. Meaning it'll get slower, but you'll still have 14 GB RAM.

 

(~edit: There's also quad channel, but consumer boards typically don't have that, so two or four sticks makes no difference)

how slower exactly?

[Eigenvektor]

24 minutes ago, kidlat017 said:

how slower exactly?

As I said, half the bandwidth (50% less). This does not necessarily mean stuff will be 50% slower in practice, but depending on the software/game it can still make a considerable difference.

 

Here's some benchmarks for various games:

https://www.hardwaretimes.com/single-channel-vs-dual-channel-ram-which-one-is-better/

You can see that frame rate in some games goes down a lot if you go from dual channel to single channel

[kidlat017]

16 hours ago, Eigenvektor said:

As I said, half the bandwidth (50% less). This does not necessarily mean stuff will be 50% slower in practice, but depending on the software/game it can still make a considerable difference.

 

Here's some benchmarks for various games:

https://www.hardwaretimes.com/single-channel-vs-dual-channel-ram-which-one-is-better/

You can see that frame rate in some games goes down a lot if you go from dual channel to single channel

so having 4,4,2,4 gb sticks in the board means i went from dual to single channel? would this just mean that I may as well just remove the other 2 and 4gb stick?

[Bat-LB]

Is there any good reason why you would start to sell your RAM Sticks? If you sell the 4 GB Ram Stick, you can pretty much sell 2 and only use 2x4 GB in Dual Channel. Replacing the 4GB with a 2GB Stick makes not much sense.

[kidlat017]

4 minutes ago, Bat-LB said:

Is there any good reason why you would start to sell your RAM Sticks? If you sell the 4 GB Ram Stick, you can pretty much sell 2 and only use 2x4 GB in Dual Channel. Replacing the 4GB with a 2GB Stick makes not much sense.

yeah im gonna go with this answer

[Eigenvektor]

8 hours ago, kidlat017 said:

so having 4,4,2,4 gb sticks in the board means i went from dual to single channel? would this just mean that I may as well just remove the other 2 and 4gb stick?

It's a bit more complicated than that. Simple answer: Dual channel requires identical RAM sticks for best compatibility.

 

You can imagine it like RAID 0 for RAM. Your CPU can split the data between the sticks, so that it can read and write to them simultaneously. This gives you double the bandwidth. But it usually requires the sticks to have the same size. Instead of a 64 bit wide bus you have an 128 bit wide bus, because it basically treats two sticks like one stick with double the pins.

 

But: Some boards/CPUs also support something called flex mode, where you can get (partial) support for dual channel, even with different sizes.

 

For example if you have 4 + 2 and flex mode is supported, then half of the 4 GB stick will run in dual channel mode with the 2 GB stick and the other half will run in single channel mode. If you have 4 + 2 + 2 then it's possible for the 4 GB stick to run in dual channel mode with both (the 4 GB stick basically acts like 2x2).

 

So 4 + 4 + 4 + 2 might actually run partially in dual channel mode and partially in single channel mode, if your CPU supports that. But there's no guarantee and it might just switch to single channel mode completely.

 

~edit: Here's a bit more info: https://www.compuram.de/blog/en/single-dual-and-multi-channel-memory-modes/