Quote:
Originally Posted by HarryT
It's only a benefit, though, if your PC has more than 4GB RAM, isn't it?
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Quote:
Originally Posted by BetterRed
True, you have to have the 'more addressable memory' - memory above 3.??GB is not accessible by 32bit programs, and 64bit programs wont install unless there's at least 4GB. Chickens and eggs, Catch22, two to tango and all that  |
Even with less than 4GB, a 64-bit program can do things a 32-bit one can't; at least, it can on Windows. A comparison:
- 32-bit Windows can't address more than 3.2 GB of RAM (except if you have a version that has PAE: Physical Address Extension, but this is VERY slow).
- 32-bit programs under Windows (32 or 64-bit, doesn't matter) cannot use more than 2GB within one process.
Even if you only have 2GB of RAM, you could run a 64-bit version of Windows, and 64-bit Calibre, and convert a book that requires 8GB of RAM. It will be done using the swap-file. It'll be horribly slow, but it will work. 32-bit Calibre, on Windows 32-bit or Windows 64-bit won't be able to convert the book at all, because it'll hit the max of 2GB of memory per process.
Running 64-bit Calibre (on a 64-bit OS) doesn't gain you any speed, but it does gain you the capability to convert larger books, and convert more books at the same time, if you have enough processor cores.
I have never encountered a 64-bit program that will not install if you have less than 4 GB of RAM.