If you’ve upgraded to Vista and added 4GB of RAM, you might be wondering why your computer is only reporting 3.5GB of RAM. This is the limit of a 32bit operating system, the only real solution to this problem is to use a Vista 64bit edition, although Coding Horror has a great post on why this is happening, and where exactly that extra half a GB of memory has gone to…

Addressing more than 4 GB of memory is possible in a 32-bit operating system, but it takes nasty hardware hacks like 36-bit PAE extensions in the CPU, together with nasty software hacks like the AWE API. Unless the application is specifically coded to be take advantage of these hacks, it’s confined to 4 GB. Well, actually, it’s stuck with even less– 2 GB or 3 GB of virtual address space, at least on Windows.

OK, so we’re limited to 4,096 megabytes of virtual address space on a 32-bit operating system. Could be worse.* We could be back in 16-bit land, where the world ended at 64 kilobytes. Brr. I’m getting the shakes just thinking about segments, and pointers of the near and far variety. Let us never speak of this again.

But back to our mystery. Where, exactly, did the other 642 megabytes of my memory go?

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This entry was posted on Friday, April 11th, 2008 at 2:16 am and is filed under Question of the Month. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.