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In my Organization for routing we are using 32 bit os rather than using 64 bit os on a host with 3GB RAM.

Since 64 bit faster than 32 bit why do sometimes people use 32 bit OS rather than 64 bit.

Does 32 bit OS require less resource than 64 bit.

Also on 64 bit OS,is the size of page table entry 64 bit?

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There is no advantage to 32-bit, but if you have a 32-bit processor, that's what you have to use. PTE's on a 64-bit system use 64-bit addresses, yes. – goldilocks Apr 15 '13 at 7:52
The x32 ABI is an attempt to merge the advantages of 32-bit mode (reduced memory use) with the advantages of 64-bit mode (more registers, new instructions, etc.). – cjm Apr 15 '13 at 21:03
up vote 0 down vote accepted

Apart from memory reasons already mentioned (64-bit apps consume more memory) there's often also a compatibility component involved - when running a lot of old or at least slightly dated software it's just safer to run on a 32-bit environment where it has been true and tested for 10+ years, instead of an unsupported platform it has never been properly tested on. While essentially the emulation layers in the AMD64 architecture and the OS layers should render this argument obsolete, there's an awful lot of very bad very old code still in production out there in the wide world - not everyone's running an up-to-date LAMP setup.

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The advantage of a 32 bits OS is that you can install it on 32 or 64 bits hardware, while 64 bits OS can only be installed on 64 bits hardware.

The size of a page table entry is 64 bits, but on current systems addresses are only implemented on 48 bits (which allow "only" 256 TB instead of 16 EB).

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32-bit applications use less ram. So sometimes it is desirable to use 32-bit OS.

There is a detail answer comparing memory usage in the askubuntu forum here.

WilQu already answer the page size question so I am not goin to repeat it here.

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