![]() UPDATE: Some readers noted that HP does provide a technical specifications page for the NC8430 stating that "all memory may not be available" above 3 GB. For example, HP's Compaq NC8430 makes use of the Intel 945PM chipset, and claims a maximum of 4 GB RAM with no caveats listed. ![]() This is not a Mac-specific issue, and it calls into question the claims some other manufacturers are making about 945PM chipset-based models being able to accept 4 GB of RAM. 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. 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. Thus, the virtual space between 3.5 GB of RAM and 3.75 GB of RAM is occupied by PCI Express data. For instance, the PCI Express RAM allocation occurs at somewhere around 3.5 GB of RAM and requires 256 MB of RAM. ![]() Between 3 GB and 4 GB, however, system memory attempts to occupy space that is already assigned to these functions. ![]() In other words, in a 3 GB RAM configuration, there is no overlap with the memory ranges required for certain system functions. However, a number of items that must be stored in physical RAM space, and when RAM reaches 4 GB, there is some overlap. The MacBook Pro Core 2 Duo presumably uses Intel's 945PM chipset, which can physically handle 4 GB of DDR2 RAM. Today we have some some additional information regarding why the units can only recognize 3 GB, and the questionable nature of other manufacturers' claims that their Core 2 Duo-based portables can address up to 4 GB of RAM. We previously reported that while the MacBook Pro Core 2 Duo can physically accomodate two 2 GB RAM modules for a total of 4 GB, Apple's specs list the model as able to recognize a maximum of 3 GB of RAM.
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