64-bit computing

64-bit computing

In computer architecture, 64-bit is a way for computers to handle information. It uses small pieces of data called bits that are 64 units wide. These bits can show numbers, memory spots, or other data.

A 64-bit computer has a special part called a central processing unit (CPU) that works with these big pieces of data. This helps the computer handle larger numbers and use more memory than older computers, which used smaller pieces like 32-bit computers.

64-bit computing is important because it helps computers manage lots of data. For example, one tiny storage spot in the CPU, called a register, can hold over 18 quintillion different values. This lets the computer work with very large numbers and keep track of many pieces of information at once. This is important for tasks like editing videos, playing games, and working with big data.

64-bit processors have been used in very powerful computers called supercomputers since the 1970s. But they didn’t become common in everyday computers until around 2003, when companies started making 64-bit versions of regular processors. Today, most personal computers and many devices use 64-bit technology because it makes them faster and better at handling modern software and large files.

Architectural implications

Processor registers are special storage spaces inside a computer that help it do calculations and manage data. They come in different types, like integer registers for whole numbers and floating-point registers for numbers with decimals.

In many modern computers, these registers are 64 bits wide. This means they can handle larger numbers and address more memory than older 32-bit computers.

High-performance computers often have special hardware for handling floating-point numbers, and many of these use 64-bit units. For example, some processors can work with 64-bit floating-point numbers, while others might use different sizes internally. This affects how the computer handles and stores data, making 64-bit systems more powerful for complex tasks.

Main article: floating-point
Main articles: x86, x87
Further information: Alpha

History

Many computers are built so that a single part can store the address to any location in the computer's memory. The number of possible addresses depends on the size of these parts. Early computers, like the IBM System/360, used 32-bit parts, which allowed for 4 GB of memory addresses. This was enough for most needs at the time.

As computers grew more powerful, they needed to handle larger amounts of memory. This led to the development of 64-bit computing, where parts can store 16 EB (exabytes) of memory addresses — far more than any computer today uses. In the 1990s and 2000s, companies like Intel, AMD, and Apple began using 64-bit processors in their computers, allowing them to run more advanced software and store huge amounts of data. Today, most computers use 64-bit processors.

Limits of processors

A 64-bit microprocessor can handle a very large amount of memory — up to 16 exabytes! But not all processors can use all of this space.

For example, the x86-64 architecture uses 48 bits for virtual memory and up to 52 bits for physical memory. This allows up to 256 TB of virtual memory and 4 PB of physical memory.

Different processors have different limits. The Power ISA v3.0 allows up to 64 bits for virtual addresses. The Oracle SPARC Architecture 2015 supports 64 bits for virtual memory. The ARM AArch64 architecture allows virtual memory sizes from 48 to 56 bits. The DEC Alpha processors started with 43 bits for virtual memory and grew over time.

64-bit applications

Changing from a 32-bit to a 64-bit system is a big change. Most operating systems need new software to work with the new hardware. But older 32-bit programs can often still work. The 64-bit system can run them directly or with special help.

One big advantage of 64-bit systems is that they can handle more memory. This is useful for tasks like editing big videos, doing science calculations, or managing large databases. Even if you don’t have a lot of memory, 64-bit systems have other benefits. Some programs can run faster because they have more space. Systems that need to do many tasks at once also work better on 64-bit setups. Big companies like IBM, HP, and Microsoft use 64-bit systems for their large networks.

Summary:

• A 64-bit processor works best with 64-bit software.
• A 64-bit processor can often run older 32-bit programs.
• A 32-bit processor cannot run 64-bit software.

64-bit data models

In 32-bit programs, pointers and data types like integers are usually the same size. On 64-bit machines, this is not always true. For example, in many programming environments, regular integers stay at 32 bits, while larger numbers and pointers grow to 64 bits. This is called the LP64 data model.

Different data models exist to manage these changes, such as ILP64 and LLP64. Most programs can adjust to these changes easily by being recompiled for the new system. The choice of data model can impact how memory is used and how devices work with the computer’s memory.

Current 64-bit architectures

Many modern computers use 64-bit architectures. This helps them handle more data and memory. These architectures include several types of processors.

Well-known 64-bit architectures include AMD's AMD64 and Intel's Intel 64. These are used in many desktop and laptop computers. There are also 64-bit versions of ARM, used in smartphones and tablets. IBM's PowerPC and z/Architecture are used in powerful business computers. Other architectures like RISC-V and SPARC also have 64-bit versions. Most of these 64-bit processors can run programs made for older 32-bit systems without losing speed.