x86-64
[11][note 2] Since the full x86-32 instruction sets remain implemented in hardware without the need for emulation, these older executables can run with little or no performance penalty,[13] while newer or modified applications can take advantage of new features of the processor design to achieve performance improvements.
Intel was forced to follow suit and introduced a modified NetBurst family which was software-compatible with AMD's specification.
The x86-64 architecture was quickly adopted for desktop and laptop personal computers and servers which were commonly configured for 16 GiB (gibibytes) of memory or more.
The primary defining characteristic of AMD64 is the availability of 64-bit general-purpose processor registers (for example, rax), 64-bit integer arithmetic and logical operations, and 64-bit virtual addresses.
[26][27][28][29][failed verification] The operating system may place additional limits on the amount of RAM that is usable or supported.
Since the basic instruction set is the same, there is almost no performance penalty for executing protected mode x86 code.
This is unlike Intel's IA-64, where differences in the underlying instruction set mean that running 32-bit code must be done either in emulation of x86 (making the process slower) or with a dedicated x86 coprocessor.
However, on the x86-64 platform, many x86 applications could benefit from a 64-bit recompile, due to the additional registers in 64-bit code and guaranteed SSE2-based FPU support, which a compiler can use for optimization.
After several years of denying its existence, Intel announced at the February 2004 IDF that the project was indeed underway.
It was eventually abandoned as of December 2024, following the formation of the x86 Ecosystem Advisory Group by Intel and AMD.
[38] Advanced Performance Extensions is a 2023 Intel proposal for new instructions and an additional 16 general-purpose registers.
[39] Codenamed "Isaiah", the 64-bit architecture was unveiled on January 24, 2008,[40] and launched on May 29 under the VIA Nano brand name.
[41] The processor supports a number of VIA-specific x86 extensions designed to boost efficiency in low-power appliances.
Power consumption is also expected to be on par with the previous-generation VIA CPUs, with thermal design power ranging from 5 W to 25 W.[42] Being a completely new design, the Isaiah architecture was built with support for features like the x86-64 instruction set and x86 virtualization which were unavailable on its predecessors, the VIA C7 line, while retaining their encryption extensions.
[43][44] These levels define specific features that can be targeted by programmers to provide compile-time optimizations.
Instruction set extensions not concerned with general-purpose computation, including AES-NI and RDRAND, are excluded from the level requirements.
[48] Compilers generally produce executables (i.e. machine code) that avoid any differences, at least for ordinary application programs.
The first ARM-based supercomputer appeared on the list in 2018[82] and, in recent years, non-CPU architecture co-processors (GPGPU) have also played a big role in performance.
Intel's Xeon Phi "Knights Corner" coprocessors, which implement a subset of x86-64 with some vector extensions,[83] are also used, along with x86-64 processors, in the Tianhe-2 supercomputer.
The 6.0-RELEASE version cleaned up some quirks with running x86 executables under amd64, and most drivers work just as they do on the x86 architecture.
Complete in-tree implementation of AMD64 support was achieved prior to the hardware's initial release because AMD had loaned several machines for the project's hackathon that year.
OpenBSD developers have taken to the platform because of its support for the NX bit, which allowed for an easy implementation of the W^X feature.
Linux was the first operating system kernel to run the x86-64 architecture in long mode, starting with the 2.4 version in 2001 (preceding the hardware's availability).
[94][95][96] 64-bit Linux allows up to 128 TiB of virtual address space for individual processes, and can address approximately 64 TiB of physical memory, subject to processor and system limitations,[97] or up to 128 PiB (virtual) and 4 PiB (physical) with 5-level paging enabled.
This removal of support has presented a problem for WineHQ (and the commercial version CrossOver), as it needs to still be able to run 32-bit Windows applications.
The solution, termed wine32on64, was to add thunks that bring the CPU in and out of 32-bit compatibility mode in the nominally 64-bit application.
The following additional characteristics apply to all x64 versions of Windows: The PlayStation 4 and Xbox One use AMD x86-64 processors based on the Jaguar microarchitecture.
[121][122] The Steam Deck uses a custom AMD x86-64 accelerated processing unit (APU) based on the Zen 2 microarchitecture.
[123] Since AMD64 and Intel 64 are substantially similar, many software and hardware products use one vendor-neutral term to indicate their compatibility with both implementations.
The term IA-64 refers to the Itanium processor, and should not be confused with x86-64, as it is a completely different instruction set.
