X86 - Complex Instruction Set Computer
X86 has become the common term used to describe a CPU instruction set compatible with the Intel 8086 and its successors.
The x86 lineage began in 1978 with the 16-bit 8086 microprocessor. They are known as CISC - Complex Instruction Set Computing - processors.
Unlike RISC, CISC instructions can perform complex tasks that take more than one cycle to execute. These can include floating-point mathematical calculations and graphics-handling instructions. CISC can be highly efficient in terms of the number of instructions per program, resulting in lower demand for code storage and RAM compared to RISC. On the other hand, a CISC processor must contain more transistors to handle the complexity of the instructions.
X86 has become the common term used to describe a CPU instruction set compatible with the Intel 8086 and its successors, including the Atom, Celeron, Pentium and Core iX processors commonly used in desktop and laptop PCs.