Thursday, August 16, 2007

Addressable Memory in 32-Bit Operating Systems

Now that is a sexy post title.

This was sent in by Loyd Case (my favorite hardware writer, bar none), and it clarifies how 32-bit operating systems use memory:
Per your comment about Stranglehold... It's not true that a 32-bit OS can only address 2GB. In fact, a 32-bit OS (without fancy tricks like Intel's oddball 36-bit extensions) can address 4GB.

There are some limits imposed by the PC architecture, which assigns I/O addresses to the lower 1MB of memory space. So if you put in 4GB of RAM, Windows 32-bit only "sees" about 3GB. Some newer motherboards allow I/O remapping, so even a 32-bit OS can get a full 4GB.

There is a 2GB limit, however -- 2GB per process. So any single application (again, barring something like Intel's PAE extensions) is limited to 2GB.

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