DDR4 what's better x16 or x8 Ram?

[Jonny]

Hi Guys,

 

I'm looking to buy 4GB of DDR4 for a new MiniPC which will be running OPNSense. I've got the SSD for it but need RAM. I found the two modules of ram below, one's Single Rank x16 and the other Single Rank x8.

I know its todo with number of chips on the DIMM but what's actually better?

 

Crucial CT4G4SFS824A 4 GB Memory (DDR4, 2400 MT/s, PC4-19200, Single Rank x8, SODIMM, 260-Pin)

Crucial CT4G4SFS624A 4 GB Memory (DDR4, 2400 MT/s, PC4-19200, Single Rank x16, SODIMM, 260-Pin)

 

Jonny

[Zagna]

At stock speeds, it doesn't matter at all. They will both perform the same.

[Jonny]

Just now, Zagna said:

At stock speeds, it doesn't matter at all. They will both perform the same.

I'm not going to but what happens if I overclocked? 16x better?

[Wufflez]

3 minutes ago, Jonny said:

I'm not going to but what happens if I overclocked? 16x better?

Right, 16x is marginally better, but I would go with whatever is cheaper. This is laptop memory, so I doubt you'd be doing any overclocks.

[Jonny]

1 minute ago, Wufflez said:

Right, 16x is marginally better, but I would go with whatever is cheaper. This is laptop memory, so I doubt you'd be doing any overclocks.

Thanks for the info. Just as I thought, 16 bit chips are better. Just wanted to make sure.

[2SidedPolygon]

3 minutes ago, Jonny said:

I'm not going to but what happens if I overclocked? 16x better?

Just a theory here, I'm not actually that certain, but the x8 might perform marginally better due to less load on the memory controller.

[Mira Yurizaki]

The "x8" and "x16" distinction is a technical spec that's mostly a concern to someone who's actually writing the DRAM controller. When you're shopping around for actual memory chips, the sizes aren't in something like 1024 MB or 512MB. They're more like 512M x 2 or 128M x 8 for a 1024 MB chip. This is known as Memory Geometry. If this were something like how Micron designs some of their memory modules, an x 8 configuration would have an organization of 4 bank groups of 4 memory banks. Whereas x 16 would 2 bank groups of 4 memory banks. Technically speaking, if I'm reading the data sheet right, fewer bank groups are better because the DRAM controller can only address one bank at a time.

 

In the end though, it doesn't really matter. The DRAM controller talks to the rest of the computer via a 64-bit bus. It's going to buffer up those 64-bits before sending them on the next transfer because trying to send out data from RAM chips as soon as they come out requires more work to reassemble the data.

[Jonny]

20 minutes ago, Mira Yurizaki said:

The "x8" and "x16" distinction is a technical spec that's mostly a concern to someone who's actually writing the DRAM controller. When you're shopping around for actual memory chips, the sizes aren't in something like 1024 MB or 512MB. They're more like 512M x 2 or 128M x 8 for a 1024 MB chip. This is known as Memory Geometry. If this were something like how Micron designs some of their memory modules, an x 8 configuration would have an organization of 4 bank groups of 4 memory banks. Whereas x 16 would 2 bank groups of 4 memory banks. Technically speaking, if I'm reading the data sheet right, fewer bank groups are better because the DRAM controller can only address one bank at a time.

 

In the end though, it doesn't really matter. The DRAM controller talks to the rest of the computer via a 64-bit bus. It's going to buffer up those 64-bits before sending them on the next transfer because trying to send out data from RAM chips as soon as they come out requires more work to reassemble the data.

Just the explanation I wanted, thanks for time  

[megaclite]

On 3/6/2019 at 9:18 PM, Mira Yurizaki said:

Technically speaking, if I'm reading the data sheet right, fewer bank groups are better because the DRAM controller can only address one bank at a time.

Vise versa - The more bank groups, the more parallelism and more bandwidth.
So x8 is better a lot