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MacBook Pro & 4GB of RAM

D

danielbriggs

macrumors 6502
Original poster
Jun 13, 2006
291
1
Manchester, UK
Hi!

I know they only say two GB, but let's say 4GB was possible, either on the current MBP or the new Merom ones.

Can Mac OS X address all of the RAM? As if you max out the RAM on a Windows PC e.g. 4GB then only 3.1GB is addressable, as the rest is taken by PCI lanes and what not. With the new 64bit ones, surely it can address oodles of ram? Have I missed something. Never used a Mac before, so sorry if it is obvious. Plan to get a Merom

Just wondering.

3GB would be VERY nice though anyway.
 
32bit for up to 4GB of ram. I believe OSX can address more?? Correct me if I'm wrong.

64bit for over 4GB of ram. The Mac Pro can go up to 16GB.

Yes OSX would address all that ram if needed... Also it depends on whether the OS is compiled for 32 or 64 bit.

Nuc
 
Has anyone a good guess to why Apple doesn't allow for 4 GB in the MBP? I've heard its to expensive as a reason, but does that mean its a complicated action to programing OS X to accept it or somethign?
 
poppe said:
Has anyone a good guess to why Apple doesn't allow for 4 GB in the MBP? I've heard its to expensive as a reason, but does that mean its a complicated action to programing OS X to accept it or somethign?
Click to expand...
Do you mean why don't they build in 4 slots? Or do you just mean 2 slots, but 4 GB? I think that would be possible now, except that 2GB notebook RAM modules are up-the-butt expensive, so there's no reason to advertise the MBP's ability.

I may be wrong, though.. but there have been other threads about this and I'm pretty sure that was the consensus..
 
last I checked, you couldn't even get 2 GB modules that are the right physical size and speed for the MacBook Pro. At any price.

As for the Mac OS being able address the full 4 GB. Yup, it can. 3.1 GB is a limitation imposed by Windows, not the hardware.

In fact, since the Pentium Pro, Intel's chips have been able to address more than 4 GB of RAM, using a technology Intel calls 'Physical Address Extension', and it lets even 32-bit chips support up to 64 GB of RAM. (Each individual application can only see 4 GB, though.)
 
xfiftyfour said:
Do you mean why don't they build in 4 slots? Or do you just mean 2 slots, but 4 GB? I think that would be possible now, except that 2GB notebook RAM modules are up-the-butt expensive, so there's no reason to advertise the MBP's ability.

I may be wrong, though.. but there have been other threads about this and I'm pretty sure that was the consensus..
Click to expand...

Thought I wish they'd build four slots, I mean why not allow for 4 GBs. About 3 weeks ago Apple even specified that they do not allows 4 GB's in the MBP, and I was just curious to why anyone thought that would be. Like if its hard to make OS X take 4 GB's, besides the obvious that very few can afford it. You'd think they'd still just allow it...
 
Nuc said:
32bit for up to 4GB of ram. I believe OSX can address more?? Correct me if I'm wrong.

64bit for over 4GB of ram. The Mac Pro can go up to 16GB.

Yes OSX would address all that ram if needed... Also it depends on whether the OS is compiled for 32 or 64 bit.

Nuc
Click to expand...
The Mac Pro can go to 32GB using 4GB FB-DIMMs. It should have the same limit as the XServe which is 32GB.

The MacBooks can use 2GB DIMMs, but may have a problem using two of the 2GB DIMMs. Somebody at arstechnica was playing around with it, don't know how it ended up.

Switching to Merom won't change things until the new chipset comes out which has a 8 GB memory limit.
 
Sun Baked said:
The Mac Pro can go to 32GB using 4GB FB-DIMMs. It should have the same limit as the XServe which is 32GB.

The MacBooks can use 2GB DIMMs, but may have a problem using two of the 2GB DIMMs. Somebody at arstechnica was playing around with it, don't know how it ended up.

Switching to Merom won't change things until the new chipset comes out which has a 8 GB memory limit.
Click to expand...

They got a black screen if I remember correctly. And thats what I was talking about. Because they then contacted apple and apple said they don't allow for 4 GB's of RAM... Or did I dream this?
 
poppe said:
They got a black screen if I remember correctly. And thats what I was talking about. Because they then contacted apple and apple said they don't allow for 4 GB's of RAM... Or did I dream this?
Click to expand...
That's about where I remember it, but I never checked the thread after that.
 
treblah said:
Link to the ArsTechnica…

Cliffs: 1x2GB DIMM works, 2x2GB DIMMs do not.
Click to expand...
That's sucky, cause you know eventually those 2GB DIMMs will come down to a decent price, and people (at least those with the current MBPs) won't be able to take advantage.

Hopefully it's so far in the future that current users will have upgraded anyways.. heh
 
I Found It!

I've been searching for a soloution to this myself and ended up on this thread. Apparently, the problem lies not with Apple, but with Intel's processor. I found an excellent explanation at www.everymac.com, who consulted with MacFixIt to explain the problem. MacFixIt's reasoning is copied below.

The MacBook Pro Core 2 Duo presumably uses Intel's 945PM chipset, which can physically handle 4 GB of DDR2 RAM. However, a number of items must be stored in physical RAM space, and when RAM reaches 4 GB, there is some overlap. In other words, in a 3 GB RAM configuration, there is no overlap with the memory ranges required for certain system functions. Between 3 GB and 4 GB, however, system memory attempts to occupy space that is already assigned to these functions. For instance, the PCI Express RAM allocation occurs at somewhere around 3.5 GB of RAM and requires 256 MB of RAM. Thus, the virtual space between 3.5 GB of RAM and 3.75 GB of RAM is occupied by PCI Express data. So in a system with 3 GB of RAM, nothing is being wasted because the memory space required by PCI Express is still between 3.5 and 3.75 GB, and the installed system RAM does not violate this space. The net result is that at least 3 GB of RAM should be fully accessible, while when 4 GB of RAM installed, ~700 MB of of the RAM is overlapping critical system functions, making it non-addressable by the system. For the full article, see: http://www.everymac.com/systems/apple/macbook_pro/faq/macbook-pro-core-2-duo-3-gb-memory-limitation-details.html​


I know that applications such as Final Cut 5 can traditionally address a maximum of 4 GB of memory, so this is understandabally a tantalizing configuration, particlulary for people editing in HD. Our best posibility seems to be hoping that Intel's forthcoming Santa Rosa platform addresses this issue. According to the guys at www.broadcastengineering.com, it will.


The newer 965 (part of the Santa Rosa platform coming out early next year) offers the ability to run DDR2 RAM at 800MHz (for the coming 2.4GHz T7700 Core 2 Duo that will have an 800MHz FSB), support for 2GB memory chips (allowing 4GB using two SO-DIMMs), DirectX 10 compatible graphics, and up to a 50 percent increase in video performance over the 945. Full article at: http://broadcastengineering.com/hdtv/broadcasting_hd_editing_go/​


Assuming that this is correct, it is feasable that Apple will easily support the additional RAM on MBP models. Price, however, will likely remain an isssue, as Apple itself seems to be the only vender who supplies a 2GB stick of DDR2 SDRAM.

:cool:
 
teejaysplace24 said:
Assuming that this is correct, it is feasable that Apple will easily support the additional RAM on MBP models. Price, however, will likely remain an isssue, as Apple itself seems to be the only vender who supplies a 2GB stick of DDR2 SDRAM.

:cool:
Click to expand...

Actually it would be nice to see 4GB SO-DIMM support from Intel, but when the production specs for the mobile 965 come out we can only hope more than 2x2GB is supported.

Especially since it didn't take the 2GB DIMMs for the MacBooks to become affordable.
 
poppe said:
Has anyone a good guess to why Apple doesn't allow for 4 GB in the MBP? I've heard its to expensive as a reason, but does that mean its a complicated action to programing OS X to accept it or somethign?
Click to expand...

Apple supports more than 4GB of ram for the Mac Pro & Powermac G5 because they're 64-bit.

The Intel 945 chipset used in the current MBP isn't 64-bit, so technically it can address up to 4GB of ram but some of it is used by the system. (See post 3 above me). Santa Rosa will bring the Crestline chipset, which is 64-bit, so the maximum ram will probably be 8GB, even if apple only supports BTO options up to 4GB.
 
ehurtley said:
last I checked, you couldn't even get 2 GB modules that are the right physical size and speed for the MacBook Pro. At any price.

As for the Mac OS being able address the full 4 GB. Yup, it can. 3.1 GB is a limitation imposed by Windows, not the hardware.

In fact, since the Pentium Pro, Intel's chips have been able to address more than 4 GB of RAM, using a technology Intel calls 'Physical Address Extension', and it lets even 32-bit chips support up to 64 GB of RAM. (Each individual application can only see 4 GB, though.)
Click to expand...

Apple offers a 2GB stick as a BTO option, so you can get them in the right size and speed.

Damo
 
zioxide said:
Apple supports more than 4GB of ram for the Mac Pro & Powermac G5 because they're 64-bit.

The Intel 945 chipset used in the current MBP isn't 64-bit, so technically it can address up to 4GB of ram but some of it is used by the system. (See post 3 above me). Santa Rosa will bring the Crestline chipset, which is 64-bit, so the maximum ram will probably be 8GB, even if apple only supports BTO options up to 4GB.
Click to expand...

I know that. That is why I asked why I can't Apple doesn't allow 4gb's. Not why it doesn't allow 16 or 32 on my MBP but 4gbs. Because I am able to buy 2 x 2gb's sticks, but the Computer will not address ithe second last .75gb's or so I heard...
 
Macbook Pro C2D and 2x2GB

I installed 2 x 2GB sticks into my Macbook Pro C2D (not Santa Rosa). The laptop works fine. But this didn't give me a single bit more of memory in OS X than with a 1GB + 2GB configuration.
I also booted Linux (64 bit Ubuntu 6.10/Edgy Eft). This also could only make use of 3 GB. However, there was quite a hole of at least 1/4 GB, where the address space was not used as I/O memory. But still, this was not used by the OS.
 
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