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3GB or 2GB dual-channel?

D

Demon Hunter

macrumors 68020
Original poster
Mar 30, 2004
2,284
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The new MBP and iMac support up to 3GB of RAM, but this disables the dual-channel capability (2GB, 2x1 GB). Does anyone know which is better? I'm thinking about performance in games, video editing, Photoshop rendering, etc.

Also, why isn't 4GB supported? Is that a limitation of the Napa chipset?
 
Demon Hunter said:
The new MBP and iMac support up to 3GB of RAM, but this disables the dual-channel capability (2GB, 2x1 GB). Does anyone know which is better? I'm thinking about performance in games, video editing, Photoshop rendering, etc.

Also, why isn't 4GB supported? Is that a limitation of the Napa chipset?
Click to expand...

There was supposed to be Napa 2 that enables core 2 duo to be used as a 64-bit chip, I saw dell touting their laptops as 64-bit and that you can use 4GB with a 64-bit operating system and lenovo and HP have 4gb options also. Now whether Napa 2 is a firmware upgrade or new boards I don't know and couldn't seem to find out just searching the web. Hopefully someone else can shed some more light on the technicalities of it.
 
Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.
 
JAT said:
Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.
Click to expand...

From what I've read, the increase in bandwith is quite dramatic, but apparently this doesn't affect system performance much? :confused:
 
JAT said:
Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.
Click to expand...

I heard it was the other way round.
 
Umbongo said:
There was supposed to be Napa 2 that enables core 2 duo to be used as a 64-bit chip, I saw dell touting their laptops as 64-bit and that you can use 4GB with a 64-bit operating system and lenovo and HP have 4gb options also. Now whether Napa 2 is a firmware upgrade or new boards I don't know and couldn't seem to find out just searching the web. Hopefully someone else can shed some more light on the technicalities of it.
Click to expand...
Napa 2 or even 64 is still out there somewhere. Did we EVER confirm it's existence?
 
Demon Hunter said:
From what I've read, the increase in bandwith is quite dramatic, but apparently this doesn't affect system performance much? :confused:
Click to expand...
The increase in bandwidth at a specific point in the RAM system is double if RAM chips are matched. But the way the overall system uses the RAM makes the real-world benefit tiny. You can search for the Intel white paper on the memory system if you want. It barely even mentions dual-channel issues.

I have zero complaints about the speed of my wife's 1GB + 256MB RAM Macbook. WAY better than the stock 256MB + 256MB since Tiger really needs more than 512 to run much.

Now, the Mac Pro is a different story.
 
It still is dual channel you have two dimms of ram it doesn't matter what size as long as you have two dual channel ram sticks.
 
I can't seem to find the thread, but someone posted a link with benchmark testing on a dual channel vs non dual channel RAM and they tested EXACTLY the same when not used with Integrated Graphics Cards.
 
Carguy172 said:
It still is dual channel you have two dimms of ram it doesn't matter what size as long as you have two dual channel ram sticks.
Click to expand...

This says otherwise:

Wikipedia said:
Each memory module in each slot should be identical to the one in its matching slot. It's also possible to use similar memory sticks from different manufacturers or different production series as long they are of the same size, specification, the same number of memory chips and internal organization.
Click to expand...
 
Demon Hunter said:
This says otherwise:
Click to expand...

This entire discussion is faulty.

In just about all Benchmark Testing, Dual Channel Ram shows no advantage over mispaired Ram in computers with non-integrating graphics cards.
 
break out a soldering iron and put those 1gb sims on the video ram. That'll show apple!
 
Dual channel will be enabled with memory sticks of different sizes. So as long as you have two sticks then you'll have dual channel.

EDIT: Straight from the horses mouth! Dual channel is enabled with intels flex memory technology!

Intel Flex Memory Technology said:
Facilitates easier upgrades by allowing different memory sizes to be populated and remain in dual-channel mode.
Click to expand...
 
TBi said:
Dual channel will be enabled with memory sticks of different sizes. So as long as you have two sticks then you'll have dual channel.
Click to expand...

See post #14...
 
Demon Hunter said:
This says otherwise:
Click to expand...
What did you look up on Wiki? Just because some RAM buses are dual channel doesn't mean all of them are. And Wiki is not infallible.

If memory serves:
The mobile setup on most Intel Macs is not full dual channel like the Mac Pros, which won't even function without paired memory. It can make some use of memory interleaving, I believe. In which case speed is a bit higher with matching RAM. But it is only actually used with the models with integrated graphics cards. And it doesn't make that much difference in the first place. Maybe if you are a hard-core gamer with high video demands, but what are you doing with a MB in that case, anyway? Anyway, the thread asked about iMac and MBP with dedicated cards, and these models do not see a benefit from matched RAM sticks.
 
Umbongo said:
There was supposed to be Napa 2 that enables core 2 duo to be used as a 64-bit chip, I saw dell touting their laptops as 64-bit and that you can use 4GB with a 64-bit operating system and lenovo and HP have 4gb options also. Now whether Napa 2 is a firmware upgrade or new boards I don't know and couldn't seem to find out just searching the web. Hopefully someone else can shed some more light on the technicalities of it.
Click to expand...

While some PC manufacturers offer 4GB options, Windows XP (home, media, and pro) only recognizes 3GB (something many people may not know).

I, too, would be interested to know if the limit for hardware to use 3GB is a restriction of the current boards or a firmware issue. Not that I really need 4GB now, but being currently limited by my computer (really old Dell that will only recognize 768meg), I don't want to spend money on a new machine with such a low ceiling of upgradability.

Originally I intended to buy when my finances will allow, but the more I consider the boat I am in now (and my unwillingness to be there again), the more I think I will wait until this particular issue is resolved, be it with the Santa Rosa platform (if that will indeed resolve it) or some type of firmware update. Luckily, I am buying for "want" and not "need", so I can afford the time spent waiting.
 
ready2switch said:
While some PC manufacturers offer 4GB options, Windows XP (home, media, and pro) only recognizes 3GB (something many people may not know).

I, too, would be interested to know if the limit for hardware to use 3GB is a restriction of the current boards or a firmware issue. Not that I really need 4GB now, but being currently limited by my computer (really old Dell that will only recognize 768meg), I don't want to spend money on a new machine with such a low ceiling of upgradability.

Originally I intended to buy when my finances will allow, but the more I consider the boat I am in now (and my unwillingness to be there again), the more I think I will wait until this particular issue is resolved, be it with the Santa Rosa platform (if that will indeed resolve it) or some type of firmware update. Luckily, I am buying for "want" and not "need", so I can afford the time spent waiting.
Click to expand...

If you are wondering why the iMac and MBP has a 3GB ceiling, it is a cost issue.

2GB so-dimms are not cheap. I believe that 4GB will work on the CD iMacs as well as MBP/MB. It is just so expensive to fit one with 2 2GB so-dimms. Maybe Apple wanted to give more options, but as you can see the 3GB upgrade is not cheap.

There is no hardware or software limit on a Mac with OS X, it is a matter of cost that Apple is not offering 4GB. I challenge someone to buy 2 2GB dimms and give it shot. I bet it will work.
 
Demon Hunter said:
See post #14...
Click to expand...
Yeah, I know that you need identical sticks for dual channel. CPU-Z seems to keep reporting my 1.5 GB of RAM as being in Dual and not single. I do the same thing on my other PC's here and it reverts to single channel.
 
suneohair said:
If you are wondering why the iMac and MBP has a 3GB ceiling, it is a cost issue.

2GB so-dimms are not cheap. I believe that 4GB will work on the CD iMacs as well as MBP/MB. It is just so expensive to fit one with 2 2GB so-dimms. Maybe Apple wanted to give more options, but as you can see the 3GB upgrade is not cheap.

There is no hardware or software limit on a Mac with OS X, it is a matter of cost that Apple is not offering 4GB. I challenge someone to buy 2 2GB dimms and give it shot. I bet it will work.
Click to expand...
It has been tried. (article on arstechnica) a single 2 Gb module does run in a MB CoreDuo. Any combination of 2 + another module fails to boot. So you're no further ahead than 2 x 1 Gb SODIMMs

Apple quite explicitly says that you can install 2 x 2 Gb into a C2D Mac, but only 3 Gb will be recognized, not 4.

It is not a cost-of-chips issue.

Reply to other posts above: Dual channel access is implemented in all of the intel Macs when two matching modules are installed - it is not limited to the integrated video machines. You may argue what the net, real-world benefit of it is in different machines, but it is still active.

Dual channel access requires 2 RAM modules of the same speed, size and composition.
 
Eidorian said:
Yeah, I know that you need identical sticks for dual channel. CPU-Z seems to keep reporting my 1.5 GB of RAM as being in Dual and not single. I do the same thing on my other PC's here and it reverts to single channel.
Click to expand...

You don't need identical sticks, just two. Then again that could be only with AMD processors.
 
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