HARDWIRED CONTROL

To execute instructions, a computer's processor must generate the control signals used to perform the processor's actions in the proper sequence. This sequence of actions can either be executed by another processor's software (for example in software emulation or simulation of a processor) or in hardware. Hardware methods fall into two categories: the processor's hardware signals are generated either by 'hardwired control', in which the instruction bits directly generate the signals, or by microprorammed control in which a dedicated microcontroller executes a microprogram to generate the signals.
Before microprocessors, hardwired control usually was implemented using discrete components, flip-chips, or even rotating discs or drums. Microprogramming made it possible to re-wire, as it were, a computer by simply downloading a new microprogram to it. This required dedicated hardware or an external processor. For example, some of DEC's PDP-10 processors used a PDP-11 as a front-end which uploaded a microprogram to the main procedssor at boot time.
Traditionally, a sewing machines' stitch patterns and a washing machine's wash programs were implemented as hardwired, usually mechanical, controls. In modern machines, these are instead implemented as software which controls a computer which controls the machine hardware. This makes it possible, for example, to download additional stitch patterns for a small fee or upgrade a machine without having to buy a complete new machine. It also opens up for intellectual property rights issues.