- 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.
The only known second source manufacturer of 4004 microprocessors was National Semiconductor.
4004 major features and related families: