Stephen Powell wrote: > By the way, there's something I don't understand. A 32-bit processor can > only access 4G of "real" (extended) memory, right? So why are there > motherboards available for 32-bit processors that support installing > more than 4G of RAM? What good is memory that the processor can't address? With PAE (physical address extensions) the processor *can* address more than 4G of ram. A single process is still limited to 32-bits which usually works out effectively to 3G of ram but the operating system can make use of more than this. It can be used for filesystem buffer cache and for multiple 3G programs. A machine with 6G of ram for example could run two 3G program at the same time and hold them both in memory without swapping. Or run one 3G program and still have 3G for the system to use in filesystem buffer cache. With PAE having more than 4G of memory is quite useful. Using PAE does have a small performance impact. It slows things down by 2%-3% in my use cases. But the increase in ram for buffers usually more than makes up for the differences. Bob
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