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MacBook Pro Core 2 Duo (Late-2006) (#2): Expensive 2 GB modules required for maximum RAM, cannot be matched
Expensive 2 GB modules required for maximum RAM, cannot be matched Core 2 Duo (Late-2006) MacBook Pros can be expanded to 3 GB of memory, unlike their predecessors (Early-2006, Core Duo MacBook Pros) which could only be -- officially -- expanded to 2 GB of RAM.
Unfortunately, achieving the maximum RAM configuration requires installation of an inordinately expensive 2 GB RAM module. OWC, for instance, offers the new 2 GB module (manufactured by Samsung) for US$680.
Also, note that by installing the maximum 3 GB of RAM, it is impossible to match RAM pairs. In order to install the maximum RAM, one 2 GB module and one 1 GB module must be installed. Installing two 2 GB modules would net 4 GB of installed RAM, but the system would only recognize 3 GB. Not only would the purchaser be wasting several hundred dollars on the bigger module, but it is unclear if matched-pair speed benefits would be apparent.
Strangely, the board likely used in the new MacBook Pros, the Intel 945PM, supports 4 GB of RAM according to specifications. As such, it is undetermined why the Late-2006 MacBook Pros can address only 3 GB.
Feedback? Late-breakers@macfixit.com.
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"...a limitation in the 945 chipset (at least the 945G/GM, unsure about 945PM) where it can't address all 4GB of memory due to how some of that memory is remapped for things like PCI/PCIe bus addressing (the 945 chipset supposedly does this so that 32-bit Operating Systems can see and use that hardware). Only 3.2GB is addressable by the OS and applications."
From a DIY Intel motherboard company's knowledge base:
If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:
- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices
ASUS datasheeet
The following tech advisory includes a memory map that's oriented toward the Windows OS, but I imagine Apple's is similar:
Intel Tech Advisory