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[[Image:Amstrad RS232.jpg|thumb|right|250px|The Pace RS232 interface, as sold by Amstrad]]
[[Amstrad]] released two [[RS232]] interfaces, both using the same input/output addresses - and, ultimately, therefore establishing the standard for serial interfaces. The main difference between the interfaces is that they contain different firmware, and the older one required an external power supply. === Original serial interface ===
Amstrad's first serial interface was one of the original peripherals released for the CPC. It was remarkable (in a bad way) for the necessity for an external, brick-like power supply.
Because of the external power supply and the poor quality of the software, this model failed to establish itself as the "standard" serial interface in the way that (say) the [[DDI-1]] did for disc drives. This allowed other serial interfaces to flourish, such as those sold by [[Cirkit]] and [[KDS]].
=== Pace serial interface ===
As a result, Amstrad dropped their original design and instead chose to remanufacture a [[Pace]] design. This included significantly improved hardware (a more compact interface and no external PSU) and vastly superior software.
