Introduced in 1974 as a successor to the Intel 4004, the 4040 was produced with a 10 μm process and includes silicon gate enhancement-load PMOS logic technology.

General performance, bus layout and arithmetic logic unit (ALU) were identical to the 4004.

Two more implemented a halt/stop system, which put the processor into a low-power mode and also allowed for single-step operation that made debugging much easier.

Additionally, the internal register file and pushdown stack were expanded to support rapid interrupt processing.

It also had four 12-bit registers for holding addresses, the top-most was the program counter and the next three operated as a push-down stack for subroutine calls.

As interrupts also need to save a return address, the stack register file was expanded to seven entries, up from three.

The handler code would then use these eight registers for any local data, leaving the original values untouched.

When the processor was in stopped mode, most of the chip hardware put into a low-drain, high-impedance condition, reducing power use.

[6] According to Byte magazine, the first third-party microcomputer designed around the Intel 4040 was the Micro 440, released by Comp-Sultants of Huntsville, Alabama, in late 1975.