Intel 4004
- The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. It was the first commercially available microprocessor by Intel. The chip design started in April 1970, when Federico Faggin joined Intel, and it was completed under his leadership in January 1971. The first commercial sale of the fully operational 4004 occurred in March 1971 to Busicom Corp. of Japan for which it was originally designed and built as a custom chip. In mid-November of the same year, with the prophetic ad "Announcing a new era in integrated electronics", the 4004 was made commercially available to the general market.
Intel 4004 was the first commercially available single-chip microprocessor in history. It was a 4-bit CPU designed for usage in calculators, or, as we say now, designed for "embedded applications". Clocked at 740 KHz, the 4004 executed up to 92,000 single word instructions per second, could access 4 KB of program memory and 640 bytes of RAM. The Intel 4004 was a part of MCS-4 chipset, which included the following chips:
- 4001 - 256-bit mask ROM and 4-bit I/O device,
- 4002 - 320-bit RAM and 4-bit I/O device,
- 4003 - 10-bit shift register,
- 4008 and 4009 - standard memory and I/O interface set.
- Although the Intel 4004 was a perfect fit for calculators and similar applications it was not very suitable for microcomputer use due to its somewhat limited architecture. The 4004 lacked interrupt support, had only 3-level deep stack, and used complicated method of accessing the RAM. Some of these shortcomings were fixed in the 4004 successor - Intel 4040.
- As the first single-chip microprocessor, the Intel 4004 is very popular with CPU collectors and non-collectors. Earlier Intel C4004 CPUs in white ceramic package are sought-after by beginner and intermediate collectors, and are usually sold for hundreds of dollars.
