Historically, the Intel 4004 processor is the first central processing unit( CPU) designed as an integrated circuit( IC). It was introduced in 1971, consisted of 2,300 transistors, which corresponded to LSI technology, Large Scale Integration, and had an instruction set of 46 instructions.
The 4004 is a microprocessor with a data bus width of 4 bits and an address space of 12 bits, corresponding to a memory addressing area of 4 KB. The 4004 was clocked at 740 kHz and had a computing power of 60,000 4-bit instructions per second, equivalent to 0.06 MIPS. PMOS technology at the time was based on structure widths of 10 µm.
The improved successor to the 4004 is the 4040.