How much does 2-channel, paired memory access help?

[Tagny Daggart]

I'm not sure if this is the correct forum for this, but, I was curious if anyone has tested to see what effect using the dual-channel memory access has on performance?

In other words, if I use mis-matched memory, or put them in the wrong slots on my motherboard, how much would this effect performance?

Geekbench scores with and without paired memory would be great.

 

[thelostswede]

Welcome to 2006...
No really, you're asking a question that you'd really end up having to test by yourself.

Besides, Intel solved the miss-matched memory size problem some years ago and gives you nigh-on full performance even with different size modules.

There's a performance penalty going single channel and with the cost of memory today, why would you even bother?

 

[Tagny Daggart]

There's a performance penalty going single channel and with the cost of memory today, why would you even bother?

I wouldn't. =)

But my Late 2008 MBP has 6GBs crammed in as mis-matched pairs (1x 2GB, 1x 4GB) and I was just curious how much of a penalty I was suffering. I did it this way because–at the time–the machine only officially supported 4GB but some folks had some luck with 6GB. I think in later versions of the OS, even 8GB worked, but at the time, 8GB was known to not work.

Thanks for the fast answer, and you're right, I shall test this myself once I get my kit. I should be ordering it this week! =) =) =)

 

[powerpcg5]

But my Late 2008 MBP has 6GBs crammed in as mis-matched pairs (1x 2GB, 1x 4GB) and I was just curious how much of a penalty I was suffering. I did it this way because–at the time–the machine only officially supported 4GB but some folks had some luck with 6GB.

I did the same thing with an iMac here. Loaded with 2 + 4 sticks.

Here's what... who cares about the performance penalty (if any)?
6GB total RAM will still be better than 4GB, and there are more pros and cons in doing that vs. a matched pair of 4GB.

 

[Tagny Daggart]

But my Late 2008 MBP has 6GBs crammed in as mis-matched pairs (1x 2GB, 1x 4GB) and I was just curious how much of a penalty I was suffering. I did it this way because–at the time–the machine only officially supported 4GB but some folks had some luck with 6GB.

I did the same thing with an iMac here. Loaded with 2 + 4 sticks.

Here's what... who cares about the performance penalty (if any)?
6GB total RAM will still be better than 4GB, and there are more pros and cons in doing that vs. a matched pair of 4GB.

Totally agree. The question was mostly academic. I love having the extra 2GB and have vowed that my next machine will have minimum of 16GBs. RAM is so cheap nowadays, its silly not to max out if you can.

I'm may go to 32GB in my new build. This will certainly come to great use when I'm doing browser testing for web-apps and have a bunch of VMs running.

 

[Tagny Daggart]

OK, tested.

On my new system (i7-3770K / GA-Z77X-UD5H), installing a matched set of RAM in the correct slots provides a performance boost of +41% (according to the 'Memory performance' score on GeekBench).

Wow, quite a difference! Added +6% to my overall GB score too.

http://browser.primatelabs.com/geekbench2/818157

vs.

http://browser.primatelabs.com/geekbench2/813901

 

[thelostswede]

That's nice, but what's the real world performance difference?
I'm sure some programs will load faster and things like picture and video editing will be quicker, but for every day tasks I'm not sure it's noticeable if you compare a single 4GB DIMM to a pair of 2GB DIMMs.

 

[Tagny Daggart]

That's nice, but what's the real world performance difference?
I'm sure some programs will load faster and things like picture and video editing will be quicker, but for every day tasks I'm not sure it's noticeable if you compare a single 4GB DIMM to a pair of 2GB DIMMs.

Agree, but all I know is opening Photoshop CS6 on my new system literally takes less than 2 seconds. On my old, it takes more than a full minute.

Woohoo!

 

[Gordo74]

Think of single channel memory and dual channel memory in this way.

On a highway, single channel memory is like having 2 lanes going each way - fast, but can clog up during rush hour

On a highway, dual channel memory is like having 4 lanes in each direction - is much harder to clog and can push information faster.


Will single channel work? Yes, 2 lane highways work every day, but 4 lane highways are much preferred.