2GB or 2.5GB... Does dual channel matter?

Samwise592

macrumors regular
Original poster
Feb 4, 2007
163
0
Long Island, NY
So I've got a choice to make... with Leo arriving at my door in under 24 hours, i realized that I'm gonna need 2gb of ram to make it preform like it should, but now I've got a choice:

1.) Buy a 2gb stick and replace one of my 512 sticks for a total of 2.5GB (Not dual channel)
2.) Buy a 2gb kit (2x1gb) and run dual channel....

which one will give me better performance?
 

jsw

Moderator emeritus
Mar 16, 2004
22,910
41
Andover, MA
It all depends on how much RAM you need. If you almost never exceed 2GB in use, dual-channel is marginally faster.

If you exceed 2GB of memory needed, non-dual-channel RAM is overwhelmingly faster than virtual memory disk swapping.
 
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bigus7674

macrumors member
Jan 4, 2005
75
1
iMac C2D RAM question

Ok, so here's a question I've been pondering: the iMac C2D (pre-aluminum models) can theoretically have 2 x 2GB modules inserted but will only really use 3.3GB of the RAM (approx. 700 MB will be "lost" due to hardware limitations).

So, question is, what is better....to have 2 x 2GB modules installed and lose the 700MB but have dual-channel support (if it will even support it on this configuration) or to just have the 1 x 2BG, 1 x 1GB setup for a total of 3GB (max) and mis-matched pairs without dual-channel?
 
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Eidorian

macrumors Penryn
Mar 23, 2005
29,085
288
Indianapolis
ok. you just have to do it yourself?

what happens if you try 4GB?
Yes, it's aftermarket only.

On the 4 GB front, it'll either say there's 4 GB but only be able to use 3-3.25 GB or it just won't boot at all.

Ok, so here's a question I've been pondering: the iMac C2D (pre-aluminum models) can theoretically have 2 x 2GB modules inserted but will only really use 3.3GB of the RAM (approx. 700 MB will be "lost" due to hardware limitations).

So, question is, what is better....to have 2 x 2GB modules installed and lose the 700MB but have dual-channel support (if it will even support it on this configuration) or to just have the 1 x 2BG, 1 x 1GB setup for a total of 3GB (max) and mis-matched pairs without dual-channel?
Just go with the 3 GB.
 
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flopticalcube

macrumors G4
Ok, so here's a question I've been pondering: the iMac C2D (pre-aluminum models) can theoretically have 2 x 2GB modules inserted but will only really use 3.3GB of the RAM (approx. 700 MB will be "lost" due to hardware limitations).

So, question is, what is better....to have 2 x 2GB modules installed and lose the 700MB but have dual-channel support (if it will even support it on this configuration) or to just have the 1 x 2BG, 1 x 1GB setup for a total of 3GB (max) and mis-matched pairs without dual-channel?
Of course the dual channel, but it costs more.
 
Comment

samh004

macrumors 68020
Mar 1, 2004
2,211
87
Australia
Buy the kit 2X1 kit.
Yes, running dual channel makes a big difference.
It's marginal.

can you put a 2GB stick in a macbook?
You can put two in, it's just not worth it.

http://guides.macrumors.com/Understanding_Intel_Mac_RAM

Dual channel is 5-8% speed improvement. Generally more RAM is better.
I use 2.5GB RAM in my MB C2D 2.16

ok. you just have to do it yourself?

what happens if you try 4GB?
It only addresses 3.3GB and if you address more than 3.3GB, or you are hitting the limit, you face instability. Kernel panics etc...
 
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samh004

macrumors 68020
Mar 1, 2004
2,211
87
Australia
Eh?

The memory addressing isn't a software issue.
There was a thread on here, a forum user put 2 x 2GB sticks in a MB and said that it saw 4GB. Everyone asked questions and the end result was when the computer used as much RAM as possible it became unstable because it hit the limit and threw a wobbly.

Use search to find it, I have no idea where it is now, but it's here... somewhere.
 
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Samwise592

macrumors regular
Original poster
Feb 4, 2007
163
0
Long Island, NY
so... since that got totally off topic...

will my performance be better with 2gb of dual channel, or 2.5gb with mismatched ram?

...Before you ask, i normally have Firefox(4-10 tabs), iTunes, iChat, transmission, a few finder windows, and sometimes MS word open. (a few dashboard widgets as well)
 
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Eidorian

macrumors Penryn
Mar 23, 2005
29,085
288
Indianapolis
so... since that got totally off topic...

will my performance be better with 2gb of dual channel, or 2.5gb with mismatched ram?

...Before you ask, i normally have Firefox(4-10 tabs), iTunes, iChat, transmission, a few finder windows, and sometimes MS word open. (a few dashboard widgets as well)
You'll be better off with more RAM.

There was a thread on here, a forum user put 2 x 2GB sticks in a MB and said that it saw 4GB. Everyone asked questions and the end result was when the computer used as much RAM as possible it became unstable because it hit the limit and threw a wobbly.

Use search to find it, I have no idea where it is now, but it's here... somewhere.
I remember quite a few threads like that but I don't remember the instability being software based.
 
Comment

flopticalcube

macrumors G4
so... since that got totally off topic...

will my performance be better with 2gb of dual channel, or 2.5gb with mismatched ram?

...Before you ask, i normally have Firefox(4-10 tabs), iTunes, iChat, transmission, a few finder windows, and sometimes MS word open. (a few dashboard widgets as well)
If you are not using all of the 2G than 2X1 will be faster.

You'll be better off with more RAM.
LOL! Nice to see two opposite answers to the same question! Now I hope that settled it for you. :D
 
Comment

samh004

macrumors 68020
Mar 1, 2004
2,211
87
Australia
You'll be better off with more RAM.
I was/am in exactly the same situation. I have a 2GB module and a 512MB module and I couldn't be happier, they both run at the same temperatures and it's smoother than when it was just 1GB matched.

I remember quite a few threads like that but I don't remember the instability being software based.
I never said it was software based, but I can see how you'd get that conclusion, all I said was that it had instabilities and kernel panics. For all I know that could be paranormally based :p

I'm just repeating what I read in the thread. Now I'm going to bed. :p
 
Comment

Eidorian

macrumors Penryn
Mar 23, 2005
29,085
288
Indianapolis
I was/am in exactly the same situation. I have a 2GB module and a 512MB module and I couldn't be happier, they both run at the same temperatures and it's smoother than when it was just 1GB matched.
Same situation back on my iMac G5. I'm glad I had 1.5 GB instead of 1 GB.


I never said it was software based, but I can see how you'd get that conclusion, all I said was that it had instabilities and kernel panics. For all I know that could be paranormally based :p

I'm just repeating what I read in the thread. Now I'm going to bed. :p
I blame solar flares.
 
Comment

flopticalcube

macrumors G4
I noticed that.

Even Barefeats admits you're better off going with more RAM then strictly with dual channel.

I can get the links if you want.
It really depends if the OP is even going to reach the 2GBs with his current use. I think the bump from 2 to 2.5 is not a whole lot. If you are going to start swapping at 2, then you probably will be at 2.5 as well.

Samwise592: check to see how much blue and green is left in Activity Monitor.
 
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