respond and introduced its own x86-64 processor, the Prescott Pentium 4, in July 2004. As a result, the Itanium processor with its IA-64 instruction set is rarely used and x86, through its x86-64 incarnation, is still the dominant CPU architecture in non-embedded computers. x86-64 also introduced the NX bit, which offers some protection against security bugs caused by buffer overruns. As a result of AMD's 64-bit contribution to the x86 lineage and its subsequent acceptance by Intel, the 64-bit RISC architectures ceased to be a threat to the x86 ecosystem and almost disappeared from the workstation market. x86-64 began to be utilized in powerful supercomputers (in its AMD Opteron and Intel Xeon incarnations), a market which was previously the natural habitat for 64-bit RISC designs (such as the IBM Power microprocessors or SPARC processors). The great leap toward 64-bit computing and the maintenance of backward compatibility with 32-bit and 16-bit software enabled the x86 architecture to become an extremely flexible platform today, with x86 chips being utilized from small low-power systems (for example, Intel Quark and Intel Atom) to fast gaming desktop computers (for example, Intel Core i7 and AMD FX/Ryzen), and even dominate large supercomputing clusters, effectively leaving only the ARM 32-bit and 64-bit RISC architecture as a competitor in the smartphone and tablet market. Virtualization Prior to 2005, x86 architecture processors were unable to meet the Popek and Goldberg requirements - a specification for virtualization created in 1974 by Gerald J. Popek and Robert P. Goldberg. However, both proprietary and open-source x86 virtualization hypervisor products were developed using software-based virtualization. Proprietary systems include Hyper-V, Parallels Workstation, VMware ESX, VMware Workstation, VMware Workstation Player and Windows Virtual PC, while free and open-source systems include QEMU, Kernel-based Virtual Machine, VirtualBox, and Xen. The introduction of the AMD-V and Intel VT-x instruction sets in 2005 allowed x86 processors to meet the Popek and Goldberg virtualization requirements. AES See also x86 assembly language x86 instruction listings x86 memory segmentation CPUID Itanium x86-64 680x0, a competing architecture in the 16 & early 32bit eras PowerPC, a competing architecture in the later 32-bit and 64-bit eras Microarchitecture List of AMD microprocessors List of Intel microprocessors List of Intel CPU microarchitectures List of VIA microprocessors List of x86 manufacturers Input/Output Base Address Interrupt request iAPX Transient execution CPU vulnerability Tick–tock model Virtual legacy wires Notes References Further reading External links Why Intel can't seem to