3GB or 2GB dual-channel?

[Demon Hunter]

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?

[Umbongo]

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?

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.

[JAT]

Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.

[Demon Hunter]

Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.

From what I've read, the increase in bandwith is quite dramatic, but apparently this doesn't affect system performance much? :confused:

[daneoni]

Dual channel isn't necessary on these computers. It is moderately useful on the Mini/MB with integrated graphics, but barely.

I heard it was the other way round.

[xfiftyfour]

I heard it was the other way round.
ya heard wrong.

[Eidorian]

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.Napa 2 or even 64 is still out there somewhere. Did we EVER confirm it's existence?

[JAT]

From what I've read, the increase in bandwith is quite dramatic, but apparently this doesn't affect system performance much? :confused:
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.

[Clydefrog]

i doubt you will even notice anything if you lost dual channel

[Scarlet Fever]

the extra gig of RAM will give you more of a performace boost than the fabled dual-channel RAM.

[Carguy172]

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.

[levitynyc]

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.

[Eidorian]

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.It's called http://barefeats.com/.

[Demon Hunter]

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.

This says otherwise:

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.

[levitynyc]

This says otherwise:

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.

[tarjan]

break out a soldering iron and put those 1gb sims on the video ram. That'll show apple!

[TBi]

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 (http://www.intel.com/products/chipsets/q965_q963) mouth (http://www.intel.com/products/viiv/prodbrief.pdf)! Dual channel is enabled with intels flex memory technology!

Facilitates easier upgrades by allowing different memory sizes to be populated and remain in dual-channel mode.

[Demon Hunter]

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.

See post #14...

[JAT]

This says otherwise:
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.

[ready2switch]

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.

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.

[da5id]

It's called http://barefeats.com/.

It would be nice to see it ran with a C2D 2GB vs 3GB.

[suneohair]

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.

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.

[Eidorian]

See post #14...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.

[CanadaRAM]

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.
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.

[TBi]

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.

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

[daneoni]

ya heard wrong.

Have any facts to back that up? cos so far what you're saying is just another word of mouth so why should i take your word over the other?

[TBi]

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.

That depends on the chipset and i know for a fact that AMD overcame that limitation ages ago and i'd say intel did too.

EDIT: Straight from the horses (http://www.intel.com/products/chipsets/q965_q963) mouth (http://www.intel.com/products/viiv/prodbrief.pdf)! Dual channel is enabled with intels flex memory technology!

Facilitates easier upgrades by allowing different memory sizes to be populated and remain in dual-channel mode.

[Eidorian]

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

That depends on the chipset and i know for a fact that AMD overcame that limitation ages ago and i'd say intel did too.

EDIT: Well it seems intel didn't actually fix that.Two posts quoting me? :D

It's on Intel systems. I don't have any AMD ones. They're different sizes as well. CPU-Z still says Dual Channel mode.

[TBi]

Two posts quoting me? :D

It's on Intel systems. I don't have any AMD ones. They're different sizes as well. CPU-Z still says Dual Channel mode.

You should feel honoured. Anyway according to intel themselves the macbook pro comes with a flex memory enabled controller and flex memory enables dual channel mode with different size memory sticks!

[JAT]

Have any facts to back that up? cos so far what you're saying is just another word of mouth so why should i take your word over the other?
What is it with people that they continue to deny facts just because they don't know something? Questions are asked, then they are answered. If you don't trust answers, then......geez, I don't know what....sit at home not knowing for sure.

Fact: Apple recommends paired ram in the Mini/MB/Edu iMac, but not in the iMac/MBP.

As discussed further in this thread, the Mac Pro requires paired ram for its Dual-channel setup. None of the other Intel Macs need this. However, they can have limited improvements with paired ram for memory interleaving. But it only matters in real-world measurements on the models with integrated graphics. So, MP: pair the ram; MBP/iMac: who cares; MB/Mini/Edu: pair it if you are anal.

If you don't believe this, fine. I give up. Buy one of each model of the computers and the ram and do extensive testing yourself.

[Eidorian]

You should feel honoured. Anyway according to intel themselves the macbook pro comes with a flex memory enabled controller and flex memory enables dual channel mode with different size memory sticks!I guess my iMac should fall under that with the same 945 chip set right?

[TBi]

I guess my iMac should fall under that with the same 945 chip set right?

Yep and that's why CPU-Z reports yours as dual channel.

[Eidorian]

Yep and that's why CPU-Z reports yours as dual channel.Well I still want to bump up to 2 GB once the prices go down. I'll just add another identical Patriot stick of RAM.

[Demon Hunter]

You should feel honoured. Anyway according to intel themselves the macbook pro comes with a flex memory enabled controller and flex memory enables dual channel mode with different size memory sticks!

Finally, a straight answer! :D

[Eidorian]

http://www.google.com/search?client=safari&rls=en&q=Intel+Flex+Memory+Technology&ie=UTF-8&oe=UTF-8

It also shows up on this chipset list. A LOT!

http://www.intel.com/design/chipsets/express_flyer.htm

[robcts]

i would think 3GB would outperform any additional benefits from a 'dual channel' setup with 2GB.

[Eidorian]

An explanation for 3 GB instead of 4 GB.

http://www.macfixit.com/article.php?story=20061027080510835

[ready2switch]

An explanation for 3 GB instead of 4 GB.

http://www.macfixit.com/article.php?story=20061027080510835

Thanks for the link. I find it really odd, but I guess if you want more than 3gig you'll have to wait for Santa Rosa (assuming it will address the problem).

[TBi]

i would think 3GB would outperform any additional benefits from a 'dual channel' setup with 2GB.

But you get dual channel with both 3GB and 2GB so why worry?

[adiosk8]

3 gigs > 2 gigs matched pairs. But if you aren't really going to use more then 2 gigs and if you don't have the money for a 2 gig dimm..then I don't think its worth it.

[TBi]

3 gigs > 2 gigs matched pairs. But if you aren't really going to use more then 2 gigs and if you don't have the money for a 2 gig dimm..then I don't think its worth it.

As said (by intel themselves), you get dual channel with any two sticks of ram so why worry?