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In this article:
- What is 64 bit computing
- Comparision of 64 bit and 32 bit computing
- Advantages and disadvantages of 64 bit computing
What is 64-bit computing?
64-bit computing makes use of 64-bit notations for its processing. In a 64-bit system, integers, memory addresses, and other data units are made up of 64 bits or 8 bytes. Those CPUs and ALUs which are based on a 64-bit architecture make use of registers, address buses, or data buses of the size 64 bit.
64-bit CPUs find application as servers and more recently as personal desktop and laptop computers. Examples of such personal 64-bit machines include the AMD64 and the 64-bit PowerPC processor.
One notable point in this case is that 64-bit CPUs may make use of external data buses or address buses of a different size also. These external components can be greater or smaller in size than the CPU itself. Usually, however, when a CPU is referred to as being 64-bit, it means that its integer registers are 64-bit wide.
Although a CPU may be 64-bit internally, its external data bus or address bus may have a different size, either larger or smaller, and the term is often used to describe the size of these buses as well. For instance, many current machines with 32-bit processors use 64-bit buses (e.g. the original Pentium and later CPUs), and may occasionally be referred to as "64-bit" for this reason. The term may also refer to the size of an instruction in the computer's instruction set or to any other item of data (e.g. 64-bit double-precision floating-point quantities are common). Without further qualification, however, a computer architecture described as "64-bit" generally has integer registers that are 64 bits wide and thus directly supports dealing both internally and externally with 64-bit "chunks" of integer data.
Comparison of 64 and 32 bit computing
Most of the operating systems were intially meant for use in a 32-bit environment. For making them capable of dealing with a 64-bit environment, they have to reporgrammed substantially. The same applies to other application software that needs to be modified in order to work in the new environment. This process of converting an application or software to work under a different environment is called porting. Since most of the application software are still to be ported to the new 64-bit environment, a hardware compatibility mode is used to run them in a 64-bit environment which makes use of the older 32-bit architecture but still supports the new one. Another way to do this is to put a 32-bit processor core together with the 64-bit one for running the older programs.
A 64-bit environment is often questioned in terms of their response to a 32-bit compatibility mode. This argument questions if the compatibility mode is faster than the existing ‘made-for-32bit’ systems that are often priced low.
The 64-bit architecture has been found to work better when it comes to clustering and multi-tasking. As compared to their 32-bit counterparts, 64-bit processors are more efficient in handling such applications.
Advantages and Disadvantages of 64-bit computing
The use of a 64-bit architecture has two important advantages which are as follows:
- A common characteristic of Operating Systems is that they keep a part of the address space meant for processes reserved for the operating system itself. This is more so in 32-bit operating systems and it reduces the space available for process addresses. However, when using 64-bit operating systems, this is not an issue at all (eg., Windows 64-bit).
- Memory mapping, a process where an item connected to the processor directly (via the address bus) is used as a memory cell, is more difficult in 32-bit architectures. An example of this problem is in the case of large files. When large files are to be memory mapped by a 32-bit architecture, it cannot take in the whole file together (due to the limited memory space) and instead, only a certain part of the file is mapped to the address. This means that for accessing further areas of the file, the existing data needs to be erased and the area to be read needs to mapped to the address space. This needs to be done every time a region on the file needs to be accessed and here is where the problem lies. Since DVDs with over 4Gb of capacity are becoming commonplace, this problem would increase day-by-day.
The use of a 64-bit architecture poses a major disadvantage and this disadvantage is that as compared to a 32-bit architecture, the same amount of data stored in a 32-bit machine would take more space in the 64-bit machine. This is caused due to the increase in the size of pointers and references in the address space. What this means is that the memory space needed for a particular process is substantially more and it puts more load on the processor cache. However, this problem has been effectively solved by using a partial 32-bit model.
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