[SOLVED] Laptop memory dual channel vs single channel

[shottyjotty]

Okay my my question isn't specifically about the performance of dual channel vs single channel, but basically I'm looking at upgrading my laptops RAM.

My laptop has 2x4GB although one is soldered. Apparently however, it still runs in dual channel with an 8 or 16GB stick replacing the 4GB one. Upon looking in CPU-Z, I see that the DIMM is running in single rank rather than dual rank. Just to clarify, I know single/dual rank does not refer to single/dual channel.

My question is: If I purchased dual rank, would the system memory then run in dual rank mode, OR, am I better off just buying an 8/16GB single rank DIMM?

Thanks for any help!

 

[Fix_that_Glitch]

Single rank memory is faster than dual rank memory. If you will, single rank is like running a race on a track, only having to run around the track once to win. Dual rank memory will have to run around the track twice to win. So you are better off buying a single rank dimm.

 

[alceryes]

Looks like there some memory 'channel' and 'rank' confusion here.

Rank refers to how the memory chips on each memory module are accessed. Your computer doesn't run in any single or dual 'rank' mode. You can mix single and dual rank memory in a system but since the memory isn't a matching pair it will just run in single 'channel' mode. This is assuming the memory is compatible with the system, of course.
As Fix_that_Glitch said, single rank memory is faster than dual rank memory.

 

[shottyjotty]

Looks like there some memory 'channel' and 'rank' confusion here.

Rank refers to how the memory chips on each memory module are accessed. Your computer doesn't run in any single or dual 'rank' mode. You can mix single and dual rank memory in a system but since the memory isn't a matching pair it will just run in single 'channel' mode. This is assuming the memory is compatible with the system, of course.
As Fix_that_Glitch said, single rank memory is faster than dual rank memory.

Force of habit in my choice of words, I know a stick is either dual rank or single rank

Thanks for the answers anyway, I'll go for the single rank

 

[geofelt]

I assume this is an intel motherboard.
AMD does not seem to support mismatched ram.
Intel memory controller has the ability to run in flex mode.
Since the first 4gb is soldered, adding a 8 or 16gb stick is going to give you an unbalanced situation so far as dual channel operation is concerned.
Flex mode will run the matching 4gb in each channel in dual channel mode. The odd 4 or 12gb will operate in single channel mode.

 

[shottyjotty]

I assume this is an intel motherboard.
AMD does not seem to support mismatched ram.
Intel memory controller has the ability to run in flex mode.
Since the first 4gb is soldered, adding a 8 or 16gb stick is going to give you an unbalanced situation so far as dual channel operation is concerned.
Flex mode will run the matching 4gb in each channel in dual channel mode. The odd 4 or 12gb will operate in single channel mode.

AMD has supported mismatched RAM for a long time but it seems to be more picky. Either way, it worked, 12GB dual channel with no noticeable performance loss.