New MacBook Pro Does Not Support 8GB RAM (for now)

[ir0n]

Interestingly, when we booted Ubuntu on the machine it only reported 3 GB memory total. We don't have an explanation for that.

Luke Soules
iFixit Labs

Hey Luke,
What version of ubuntu you used in the test ? 32 bit or 64 ? 64 bit should see all 8GB of RAM.
32 bit default Ubuntu kernel won't support more than 3 - 3.5 GB of ram because it lacks PAE. You can install server kernel with apt-get ( or aptitude -whatever you like more on it to get PAE support and use all avail. RAM or you can manually compile the kernel and include PAE support.

 

[bignumbers]

Apple Hardware Test?

I suspect folks are on the right track with the firmware being a limitation.

I'm curious what Apple Hardware Test reports for available RAM. I doubt it'll show more than 4GB, but it's an easy enough test (for someone lucky enough to have a new MBP with 8GB RAM!).

 

[ifixit]

The brief testing we did with Ubuntu was with the 32-bit version, so that may explain what we saw.

With 5 GB RAM installed, the system appears to perform well. The same test of running two instances of Parallels, each allocated 2 GB of RAM, resulted in the following:

Both instances of Parallels were usable, unlike when we did the same thing with 8 GB of RAM installed.

 

[ifixit]

I'm curious what Apple Hardware Test reports for available RAM. I doubt it'll show more than 4GB, but it's an easy enough test (for someone lucky enough to have a new MBP with 8GB RAM!).

Apple Hardware Test reported the full 8 GB. We did a quick test and it passed, but didn't take the time to do an extended test.

 

[commander.data]

We suspect that this testing implies a two things:
1) The hardware can handle a 4 GB chip without any problem
2) There are OS-level limitations with 8 GB RAM on these systems.

Luke Soules
iFixit Labs

In the Merom based Core 2 Duo on the Napa Refresh platform, the chipsets "supported" 4GB in that 4GB would be detected but only 3GB would be usable because other device addresses occupied the 3-4GB space. In Santa Rosa, the chipset still only supported 4GB yet it could use all of it because Intel moved the device addresses above 4GB.

Is it possible that the situation with the 9400M chipset is similar to the Napa Refresh platform? As in the chipset will officially detect 8GB but can not actually use the full 8GB because device addresses occupy some region, perhaps in the 6GB-8GB range. Perhaps the instability is because the OS or EFI is not calibrated to prevent RAM from being allocated to those device address regions and conflicts are cropping up as they overlap. I believe this was prevented in Napa Refresh because Apple hard coded the 3GB limitation in the EFI. Apple may need to put a 7GB or something limitation in the EFI to partition out the device address space, instead of just telling people the chipset only supports 4GB of RAM and hoping no one puts more.

 

[mzeb]

Vista 64?

I know the x86_x64 distros of linux sometimes have the funny 3GB limit. Crazy question though. If you boot camp Vista 64 on there, does it report and use all 8GB? It should treat it just like any other PC laptop so it should be just fine.

 

[ir0n]

I know the x86_x64 distros of linux sometimes have the funny 3GB limit. Crazy question though. If you boot camp Vista 64 on there, does it report and use all 8GB? It should treat it just like any other PC laptop so it should be just fine.

The limit is only on x86 kernels, there is no such limit on x64 kernels in Linux. I guess the whole thing is limit of OSX and not the hardware itself. Best test would be to try any Linux x64 distro and/or Vista 64 / Xp 64.

 

[shadowfax]

The brief testing we did with Ubuntu was with the 32-bit version, so that may explain what we saw.

With 5 GB RAM installed, the system appears to perform well. The same test of running two instances of Parallels, each allocated 2 GB of RAM, resulted in the following:
...

Both instances of Parallels were usable, unlike when we did the same thing with 8 GB of RAM installed.

Luke, it looks like your experience has confirmed what was found on the previous MacBook Pros, where users found that 6 GB worked quite well, but 8 GB caused the severe instability that you experienced. This led them to speculate that the issue may be related to how the OS handles synchronously reading/writing memory to each memory bank simultaneously, a feature that only works with identically sized memory in each bank.

That may not be the explanation, but it's nice to see that there does not appear to be any low-level 4GB memory restriction.

I appreciate your work. I have a MacBook 2.4GHz, and I want to upgrade the RAM for better performance in Aperture. I was going to throw in the towel and get a 4 GB kit, but I think I may wait for the 4GB module to become affordable. Does anybody know the cheapest place to get one? Crucial is pretty dang expensive right now....

 

[Digital Skunk]

This seems to support what some have wondered in other threads where the MBP and theoretically iMac could recognize the 8GB of RAM but when it comes time to use those 8GB the hardware fails to do so.

I will hold off on buying the 4GB chips and wait for the next Mac laptop that will support 8GBs via two DIMMs standard. By that time the price will be cheap and the product widely available.

 

[gnasher729]

In the Merom based Core 2 Duo on the Napa Refresh platform, the chipsets "supported" 4GB in that 4GB would be detected but only 3GB would be usable because other device addresses occupied the 3-4GB space. In Santa Rosa, the chipset still only supported 4GB yet it could use all of it because Intel moved the device addresses above 4GB.

Is it possible that the situation with the 9400M chipset is similar to the Napa Refresh platform? As in the chipset will officially detect 8GB but can not actually use the full 8GB because device addresses occupy some region, perhaps in the 6GB-8GB range. Perhaps the instability is because the OS or EFI is not calibrated to prevent RAM from being allocated to those device address regions and conflicts are cropping up as they overlap. I believe this was prevented in Napa Refresh because Apple hard coded the 3GB limitation in the EFI. Apple may need to put a 7GB or something limitation in the EFI to partition out the device address space, instead of just telling people the chipset only supports 4GB of RAM and hoping no one puts more.

My theory which would explain the observations so far: The motherboard can address 8 GB, but the graphics cards use addresses at the end of those 8 GB. When you start the machine, the OS counts two things: How many RAM chips do you have, and how many are usable. With 4+4GB, there are two RAM chips with a total of 8 GB, but the second is not usable because it interferes with the address space of the video card, so only 1 chip = 4GB are useable. With 4+1 GB, both chips are usable, so you see 5GB and can use 5GB. With 4+2 GB, you would be able to use 6 GB. If there were 3GB chips, you would be able to use 4+3 GB.

If you have 4+4 GB, you will probably get lots of page-in/page-outs when you exceed 4GB, because the second chip is counted as free memory, but will never be used.

 

[darwinian]

Thanks for running the test. 6 GB in my Jul 2007 MBP works great. There's a thread floating around here somewhere with several confirmed reports. I bet 6 GB in your test machine would be fine, like the 5 GB.

 

[commander.data]

My theory which would explain the observations so far: The motherboard can address 8 GB, but the graphics cards use addresses at the end of those 8 GB. When you start the machine, the OS counts two things: How many RAM chips do you have, and how many are usable. With 4+4GB, there are two RAM chips with a total of 8 GB, but the second is not usable because it interferes with the address space of the video card, so only 1 chip = 4GB are useable. With 4+1 GB, both chips are usable, so you see 5GB and can use 5GB. With 4+2 GB, you would be able to use 6 GB. If there were 3GB chips, you would be able to use 4+3 GB.

If you have 4+4 GB, you will probably get lots of page-in/page-outs when you exceed 4GB, because the second chip is counted as free memory, but will never be used.

Then I guess Apple needs to do what I said in my original post and hard code a 7GB limit in the EFI for the 9400M chipset.

My current Merom Napa Refresh MacBook Pro only supports 3GB, but it's currently equipped with 2x2GB DDR2-667 CL4 memory. I've experienced no stability issues so OS X clearly can figure out how to use part of a DIMM (3GB of out 4GB in my case and presumably 7GB out of 8GB in the 9400M case) as long as the EFI prevents the device addresses range from overlapping the RAM.

 

[clemare]

32 vs 64 bits

According with the screenshots none of the applications appears to be 64 bits, wich means they can see only 4GB of RAM, however 2 instance of an application should see separated amounts of ram because the limit is virtual, I mean, 4GB for every app., and we know that leopard is 64 bits, so it should allocate 4GB for every app.

But MAYBE Mac OS allocates the first initial 4GB of RAM when using an Intel Processor because the registers used by the applications are 32 bits (wich differs from PowerPC Architecture, where the apps. have access to every register in the CPU, even when the registers are 64 or 128 bits). This limitation alse affect Windows 64 bits...

So, If you want to know if the OS can Handle more than 4 GB of RAM on the Mac Book, you need to test 64bits applications. One option is to create a very little application in Objetive C that allocates 3 GB, and then run it twice.

clemare

 

[commander.data]

According with the screenshots none of the applications appears to be 64 bits, wich means they can see only 4GB of RAM, however 2 instance of an application should see separated amounts of ram because the limit is virtual, I mean, 4GB for every app., and we know that leopard is 64 bits, so it should allocate 4GB for every app.

But MAYBE Mac OS allocates the first initial 4GB of RAM when using an Intel Processor because the registers used by the applications are 32 bits (wich differs from PowerPC Architecture, where the apps. have access to every register in the CPU, even when the registers are 64 or 128 bits). This limitation alse affect Windows 64 bits...

So, If you want to know if the OS can Handle more than 4 GB of RAM on the Mac Book, you need to test 64bits applications. One option is to create a very little application in Objetive C that allocates 3 GB, and then run it twice.

clemare

Well both Tiger and Leopard aren't fully 64-bit operating systems. The kernel is still 32-bit. A 64-bit kernel won't arrive until Snow Leopard. Tiger and Leopard can control more than 4GB of RAM because it uses PAE which allows the 32-bit architecture to address 64GB (36-bit) worth of RAM.

 

[Dejavu]

Wow, these new MacBook upgrades are like gifts that keep on giving.

 

[Abstract]

Could it be a limitation of the CPU?

It could be due to Apple's greed. Who limits their technology like this? Usually, companies are trying to offer something better and faster than their competitors. Only Apple would.

Future proofing. It's not so much about what you need today. You may want your laptop to last a few years, and by then 4GB could be limiting.

I'd like to see a poll of users who Need 8GB as opposed to 4GB

And besides futureproofing, the argument that "most people don't even need 8 GB of RAM" isn't a good excuse. It's not a good excuse at all. There are laptops that can use 8 GB of RAM, and if this is a software limitation, I expect Apple to take away the artificial limitation, because the limitation certainly isn't Leopard. Even Tiger was able to access over 4 GB of RAM in an old Mac Pro.

 

[shadowfax]

It could be due to Apple's greed. Who limits their technology like this? Usually, companies are trying to offer something better and faster than their competitors. Only Apple would.

Sounds to me like someone needs to head back to Kindergarten. Companies limit their hardware all the time, preventing consumers from using it in ways that they don't want. For example, the disabled Wi-Fi on some Smartphones, prevented by mobile carriers who wanted to force their customers to use their network and keep their bills high.

... if this is a software limitation, I expect Apple to take away the artificial limitation, because the limitation certainly isn't Leopard. Even Tiger was able to access over 4 GB of RAM in an old Mac Pro.

Again, I think you are presumptuous here. Software 'limitations' are multifaceted. You seem to think that Apple put something in their code that said, "OK, if it's this model, Don't let the users go over X amount of RAM." This is *highly* unlikely. It's much more likely that the limitation is somewhat of an architectural problem that is much more complicated to 'remove' than you suggest. I do not know the details, personally, but the way that this limitation manifests itself (as you can read yourself in this thread!) *strongly* suggests that this is not an issue artificially created by Apple, but rather something they haven't quite fixed yet. In the interest of not making yourself look foolish, you might want to hesitate the next time you jump to such harsh conclusions.

 

[Tampa Tom]

I've discovered the real reason why 8 isn't supported

The earlier MacRumors story stated:

Apple is publicly opposing Proposition 8 and making a donation of $100,000 to the No on 8 campaign.

See? Apple supports the "No on 8" campaign and so they obviously won't support 8GB or RAM for the same fundamental reason.

 

[cmuench]

The earlier MacRumors story stated:



See? Apple supports the "No on 8" campaign and so they obviously won't support 8GB or RAM for the same fundamental reason.

Best comment all night

(Not supportive of apple btw of thier decision for NO on 8)

 

[AidenShaw]

See? Apple supports the "No on 8" campaign and so they obviously won't support 8GB or RAM for the same fundamental reason.

LOL - made my night (especially after the "No on 8" thread was closed).

 

[Abstract]

Sounds to me like someone needs to head back to Kindergarten. Companies limit their hardware all the time, preventing consumers from using it in ways that they don't want. For example, the disabled Wi-Fi on some Smartphones, prevented by mobile carriers who wanted to force their customers to use their network and keep their bills high.

1. Wrong industry. Do many computer manufacturers limit their own hardware? No, because if they do, a competitor won't put that same limitation on and make any company that does look bad.

2. Mobile phone service is a service, and they make money from your access to it. Making computers is entirely different. The only reason Apple does this is because they can. They're the only company that includes OS X with their computers (and Psystar, ModBook).


What I know is that older Macs with an older version of OS X from several YEARS ago can access 8 GB (and more). If this RAM limitation is found to be an OS X issue, then it can be fixed rather easily. If this is a hardware issue, then it's an entirely different story. However, other computer manufacturers have 8 GB limits on their more expensive laptops, and I doubt they have access to technology that Apple does not have access. This is why I don't believe it's hardware.



And what a great insult. "Kindergarten." Is that really all you've got? I mean, really? Pathetic.

 

[joystik]

I run out of memory on my dell precision m6300. Currently running 4gb ddr2 667mhz. When trying to copy something from illustrator to photoshop, illustrator shuts down due to insufficient memory. I've seen illustrator use up to 800,000k at times... So I'm definitely down for 8gbs.

 

[Eidorian]

I run out of memory on my dell precision m6300. Currently running 4gb ddr2 667mhz. When trying to copy something from illustrator to photoshop, illustrator shuts down due to insufficient memory. I've seen illustrator use up to 800,000k at times... So I'm definitely down for 8gbs.

So what's keeping you from adding more RAM to that machine again?

 

[pcguru83]

My email to Steve...

Steve,

The Nvidia chipset is definitely capable of supporting 8GB of RAM. It's now been confirmed that the Macbooks however become unstable and basically won't function properly with 8GB of RAM. Why the lockout to only 4GB RAM? Will we ever see an update to allow us to use the hardware to its fullest extent? Snow Leopard maybe? Perhaps I acted prematurely, but in all honesty I purchased my new Macbook with the expectation that 8GB would be possible.

Sincerely,
xxxxx xxxxxx

We'll see what happens--surely can't hurt anything.

 

[AidenShaw]

... but in all honesty I purchased my new Macbook with the expectation that 8GB would be possible.

To me, this seems pretty silly.

Why would you "expect" the system to support more memory than advertised?