Is Maximum RAM 3GB or 4GB

The new Santa Rosa MacBook Pros (that's the new 2.2 and 2.4GHz models) can accept up to 4GB's of RAM but the older ones (like the model I think you're talking about) can only accept up to 3GB's.

Hope this helps
-Sam

Non-Santa Rosa MBPs (Core 2 Duo) can accommodate 2 GB DIMMs in each slot for a total of 4 GBs installed. However, the memory controller will only allow the use access to the first 3 GBs. The remainder of the address space is reserved to the operating system.

The new Santa Rosa MBPs have a different memory controller that gives the user full access to the 4 GBs of address space.

Michael, Kappy said it better and more accurately 🙂

-Sam

that is not 100% correct. The hardware memory controller limits memory access to 3.46 GB. Mac OS X further limits memory access to 3GB. You can install vista via bootcamp on the macbook pro and it will be able to access 3.46 GB.

Glor

If it is a santa rosa chipset (2.2 and 2.4 ghz) then it will be able to recognize and fully access 4GB. I currently have 4GB in my mbp.

Glor

The Santa Rosa (2.2/2.4 GHz) MacBook pros fully support up to 4 GB of RAM, so if you install two 2 GB modules, the fully 4 GB will be available to the system (OS & apps). The 3 GB limitation only applies to the older, non-SR MacBook Pros.

Kappy wrote :
Non-Santa Rosa MBPs (Core 2 Duo) can accommodate 2 GB DIMMs in each slot for a total of 4 GBs installed. However, the memory controller will only allow the use access to the first 3 GBs. The remainder of the address space is reserved to the operating system.

The RAM Expansion Developer Note's October 2006 MBP section says that :

Maximum memory capacity is 3 GB. If you install a 2 GB SO-DIMM in both the bottom and top memory slots of the computer, both the About This Mac window and the Apple System Profiler will show that you have 4 GB of SDRAM installed. However, Activity Monitor and other similar applications will reveal that only 3 GB of SDRAM has been addressed for use by the computer.

Even assuming that having some memory only available to the OS and not the applications is technically possible, I don't see the point of doing so. Moreover, the fact that Windows can only see 3.46 GB suggests that the memory controller cannot access all 4 GB (and saying that it will only allow the user to access 3 GB and reserve the rest to the OS just doesn't make sense - how could the memory controller make the difference between "the user" and "the operating system" ?). The end result is the same : older MBPs cannot take full advantage of two 2 GB memory modules, but your explanation doesn't seem right (FWIW, I don't know the complete answer any better).

Mac mini1.25 Ghz G41 GB RAM40 GB HDDAirPort Extreme Mac OS X (10.4.10) External 250 GB LaCie HDDLaCie FW DVD-RW DL 16x20 GB iPod w/Color Display

I think you mean 3.146 GBs at least that's what I recall from an Apple document. ATPM and System Profiler will display 4 GBs as installed.

It's not that OS X truly "limits" access to 3 GBs, rather that the address space in the upper 1 GB is already in use by the system and is therefore reported as unavailable.

I assumed that Glorfindeal was reporting the correct amount (see his post above).

It's not that OS X truly "limits" access to 3 GBs, rather that the address space in the upper 1 GB is already in use by the system and is therefore reported as unavailable.

I really don't see what you mean by "in use by the system". I don't understand how the memory controller could differentiate the system (what exactly are you referring to BTW?) and the rest. Could you please give a more detailed explanation ? I may very well know less than you do on the subject, but IMHO your explanation isn't sufficient to understand what you're trying to say.

Mac mini1.25 Ghz G41 GB RAM40 GB HDDAirPort Extreme Mac OS X (10.4.10) External 250 GB LaCie HDDLaCie FW DVD-RW DL 16x20 GB iPod w/Color Display

Well, try this:

Although the Intel 945PM chipset can physically handle 4GB of DDR2 RAM, there is the potential for "memory overlap" when more than 3GB of RAM is installed. 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.

See also:

MacBook Pro (Core 2 Duo)- Memory Specifications

It must be nice to not know the answer to your question but be so sure mine is incorrect. However, that's your privilege.

Since I have other things to do and have earnestly tried to provide an answer to your question, I'll let you do the research instead.

Good luck.

It sounds like there is some disagreement between the responders

Don't worry about that... Like Glorfindeal said, the model you are discussing will be able to access all 4GB's of RAM

-Sam

It wasn't directed towards you Michael... Look at the "in response to" section in his comment. Your question was pretty basic and no one had any issue with helping you out. The issue just got bounced back and forth regarding "why" the pre-Santa Rosa MBP would only have access to 3GB and the SR MBP would have access to 4GB.