What is the difference between 32 bit microprocessor and 64 bit microprocessor?

Answer 1

The fundamental difference between a 32-bit and 64-bit microprocessor is what their names suggest: the size of the basic integer operations, also called the 'native' size of a CPU's calculations. The native size of a CPU determines a whole bunch of related characteristics.

For instance, all integer calculations are done using the native size; this matters in terms of performance for several reasons:

• if you add two integers smaller than the native size, it requires only a single operation.
• if you add two integers larger than the native size, you must perform 3 operations (add the upper values, add the lower values, then combine).

For instance, if you wanted to add two 20-bit numbers, on both the 32-bit CPU and 64-bit CPU it would require a single operation. However, if you wanted to add two 40-bit numbers, it would require only 1 operation on a 64-bit CPU, but 3 operations on a 32-bit CPU.

The native size of a CPU also determines things like the maximum addressable memory - thus, a 32-bit CPU can address up to 2^32 = 4GB of memory, while a 64-bit system can address up to 16 Exabytes. It also determines the minimum size of information that has to be processed - when fetching information from caches and memory, no operation can be done with information less than the native size. Thus, 64-bit CPUs are more demanding on memory subsystems, as they need to process information in 64-bit chunks, rather than 32-bit ones.

Answer 2

64-bit processors can handle a larger load of information by directing twice as much data at a time than a 32-bit processor. That's the common sense part. The problem with 64-bit processors is that you will not notice any difference in speed unless your system matches the 64-bit specification. First you must have a 64-bit motherboard (64-bit bus lines) a 64-bit operating system, and 64-bit applications and software. You cannot run most 32-bit applications on a 64-bit machine. So 64-bit processors work in a 32-bit environment but an increase in speed is not noticeable unless if it is used in a 64-bit environment.

As inferred above, a 64-bit processor is capable of running a 32-bit Operating System, but the reverse is not true.

Because a 64-bit CPU processing everything in a minimum chunk size of 64-bits, this places more demands on the memory subsystem than a 32-bit CPU does - all fetches from memory must be in increments of 64-bit size, so even in the case where the data fits in 1 bit of information, a 64-bit CPU must transfer 64-bits of data from memory, while a 32-bit system only has to transfer 32-bits. There is a payoff at the larger end, though, since to transfer between 33 and 64 bits of information, a 32-bit CPU must make TWO memory transfer calls, while a 64-bit CPU can fit it into a single call (each call has non-trivial overhead, so 2 calls for 32-bits actually requires about 40% more data and time than a single 64-bit call). In a typical instruction mix, this difference in memory access mode generally means that a 64-bit CPU consumes about 10-15% more memory bandwidth than an equivalent 32-bit CPU.

Everything else being equal (and, that's never the case), a 32-bit OS running on 32-bit hardware will be about 20% faster than a 32-bit OS running on a 64-bit CPU. Comparing a 32-bit OS on 32-bit CPU vs 64-bit OS on 64-bit CPU is a bit harder.

In this later case, the differences in how the CPUs handle work means that performance is highly dependent on the workload's design itself. Workloads which perform calculations on larger amounts of data will be faster on a 64-bit system (64-bit OS and CPU), while those operating typically on smaller amounts of data will be better off on a 32-bit system. Note that this applies to both the program itself, and the data that program typically handles - it's a non-trivial issue, and one not really suitable for non-technical people to access.

Finally, of course, the most commonly noted difference between a 32 and 64-bit CPU is the maximum amount of memory the system can use. Due to memory addresses being stored in a single native word size (32- or 64-bits in width), a 32-bit system can address no more than 4GB of virtual memory, while 64-bit systems can address (theoretically) up to 16 Exabytes (4 billion times more).

Answer 3

When reading about PCs and servers, you'll often see the CPU described by the number of bits (e.g., 32-bit or 64-bit), here is what that means.

32-bit refers to the number of bits (the smallest unit of information on a machine) that can be processed or transmitted in parallel, or the number of bits used for single element in a data format. The term when used in conjunction with amicroprocessor indicates the width of the registers; a special high-speed storagearea within the CPU. A 32-bit microprocessor can process data and memory addresses that are represented by 32 bits.

64-bit therefore refers to a processor with registers that store 64-bit numbers. A generalization would be to suggest that 64-bit architecture would double the amount of data a CPU can process per clock cycle. Users would note a performance increase because a 64-bit CPU can handle more memory and largerfiles. One of the most attractive features of 64-bit processors is the amount of memory the system can support. 64-bit architecture will allow systems to address up to 1 terabyte (1000GB) of memory. In today's 32-bit desktop systems, you can have up to 4GB of RAM (provided your motherboard that can handle that much RAM) which is split between the applications and the operating system (OS)

Answer 4

If a CPU is 64-bit compatible, it means the instruction word length that it can process is 64 bits long, where a 32-bit compatible CPU can only process instructions 32 bits long.