The Acorn Eurocard systems were a series of modular microcomputer systems based on rack-mounted Eurocards developed by Acorn Computers from 1979 to 1982, aimed primarily at industrial and laboratory use, but also home enthusiasts. The experience gained in developing this modular system strongly influenced the design of Acorn's first all-in-one home computer, the Acorn Atom, released in March 1980; and also much of the circuitry in its successor, the BBC Micro, first shown in late 1981. Acorn's final rack-based machine was the System 5, released in late 1982. The Eurocard business was then sold on to one of its principal resellers, Control Universal Ltd, which continued to develop various cards for industrial use based on the Acorn-standard bus during the 1980s, but ultimately went into receivership in 1989. Eurocards Placing the two Eurocards from the original Acorn Microcomputer onto a backplane made the system straightforward to expand in a modular way. The original I/O card, minus its keypad and LED display, became the cassette interface card; while the original 6502 CPU card, slightly adapted with the addition of a keyboard interface, became the basic CPU card of the system. A series of interchangeable expansion cards were then developed: additional RAM cards; a card containing the Acorn System BASIC interpreter on ROM; a 40×25 character VDU card, and a UHF adaptor for it; interface cards; a floppy disk controller; Econet network cards; an 80×25 character VDU card; and later also alternate processor cards, offering a 6809 or a faster 6502. System 2 The Acorn System 2 was offered as a system by Acorn Computers from 1980. It was the successor to the Acorn Microcomputer (renamed the Acorn System 1). The system comprised four Eurocard-sized printed circuit boards mounted in a 19 inch sub-rack frame on an 8-slot backplane, plus a (separately supplied) additional external keyboard. The four PCB cards contained respectively: a CPU card, containing a 1 MHz 6502 microprocessor, the keyboard interface, and a 2K ROM with the cassette operating system (The 6502 card could be swapped for a 6809.) a VDU card, providing a 40×25 character teletext-standard display, based on an MC6845 CRT controller and an SAA5050 teletext character generator, a cassette interface card, a memory card with 4K of RAM and a 4K BASIC ROM. A further 4K of RAM could be added, and also an additional 4K ROM containing floating-point routines and scientific functions. The CPU card