CODEWITHSUNDEEP
memory-managementoperating-system
Ravindra Bagale
Ravindra Bagale

Reputation: 17655

memory allocation for 64 bit OS

memory is divided into two parts
1) some memory portion reserved for OS system processes
2) remaining memory for user processes.
32 bit OS allocates 4GB memory for OS processes. like this how many memory space is allocated for 64 bit OS(memory space only for system processes i.e. OS processes). This question was asked me in interview

Upvotes: 0

Views: 2684

Answers (3)

bart s
bart s

Reputation: 5100

Maximum memory address space is depending on the OS version that you have.

See Physical Memory Limits: Windows 7

Some more reading on this in Pushing the Limits of Windows: Physical Memory and Pushing the Limits of Windows: Processes and Threads

Upvotes: 0

user1802174
user1802174

Reputation: 273

Really not that true after all.

Windows comes with more than just 1 kernel or variations.

For example there are Windows OSs on the market with a kernel with PAE support, this is enough to demonstrate that your statement is not true.

Also 32 bit desktop versions of Windows are not capable to provide 4Gb of addressable memory but only ~3.5 .

edit refer to this link for detailed informations.

Upvotes: 0

Brian Agnew
Brian Agnew

Reputation: 272277

It's not clear to me how specific this question is to Windows. From a generic perspective 232 gives you ~4 billion i.e. 4GB. So 264 would give you 16 exabytes (!)

See here for more info.

A 64-bit register can store 264 (over 18 quintillion) different values. Hence, a processor with 64-bit memory addresses can directly access 264 bytes(=16 exbibytes) of byte-addressable memory.

Note the provisos re. the external buses. Just because the CPU registers are 64-bit wide it doesn't necessarily imply that the external buses will be the same width. Consequently the CPU and machine architecture together will determine the practical limitations. Note the section marked Limitations of Practical Processors.

Upvotes: 2

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