memory - When 32 bit machine can access max of 4GB RAM, how does it access 150GB of HDD -


i understand memory size can accessed 32 bit machine limited 4gb. since there i/o ports pcie, usb, serial, parallel, ps/2, audio i/o, cd drive, floppy drive, memory card readers e.t.c have dealt well, result less 4gb ram supported cpu itself. things have mentioned , others take quite bit of memory also.

now confused how can support several gb of hard disk space? how able access upto 1 tb of external storage through these sata/ata interfaces. same goes usb mass storage devices external usb hard disks well, suprised such big storage can accessed cpu while being limited 32 bits. there no limit how big hdd can supported 32 bits processor?

not sure begin :-)

this very-very simplistic explanation, not true ever since 286, might grasp basic concepts:

memory addressing done via address bus: 32 bit address bus can express 2^32 different addresses. smallest amount of memory manipulable in 1 operation called "word" size, limited width of data bus.

the maximum amount of addressable memory word size times number of addresses.

in "block io" operations, equivalent of word size block size, bigger. trade-off: larger data can accessed same address length, flipping single bit requires overwriting whole block.

the bigger difference address not need present @ same time on "address bus" in memory: commands (and responses) transmitted in sequential "packets", on network. there no hardware-imposed limit on address size, albeit sure protocol specifies reasonable upper bound.

as can see, addressable disk size unrelated cpu bus widths , register sizes.


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