The Cromemco Octart was an expansion card made by Cromemco for their range of S-100 bus based computer systems. The card provided eight serial bus channels and a single bi-directional parallel port. The serial connections were often used to interface eight computer terminals to the host system. In combination with the Cromemco Cromix multi-user operating system, this allowed different users to concurrently work on the system. The parallel port was typically connected to an IEEE 1284-type printer.
In computing, the expansion card, expansion board, adapter card or accessory card is a printed circuit board that can be inserted into an electrical connector, or expansion slot, on a computer motherboard, backplane or riser card to add functionality to a computer system via the expansion bus.
Cromemco was a Mountain View, California microcomputer company known for its high-end Z80-based S-100 bus computers and peripherals in the early days of the personal computer revolution.
The S-100 bus or Altair bus, IEEE696-1983 (withdrawn), is an early computer bus designed in 1974 as a part of the Altair 8800. The S-100 bus was the first industry standard expansion bus for the microcomputer industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders implemented drivers for CP/M and MP/M. These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC.
Octart superseded Cromemco's TUART and QUADART and IOP boards. Unlike earlier boards, which merely formatted and exchanged individual data characters, the Octart featured a sophisticated DUART communications circuit plus an independent Z80A processor with 64 KB bytes of memory. This enabled the Octart to:
Perform all protocol and error-detection/recovery functions.
Buffer large amounts of serial data.
Pass only preprocessed data over the host bus using interrupt-driven I/O.
This reduced the processing load on the host computer's central processing unit and dramatically increased system throughput.
A central processing unit (CPU), also called a central processor or main processor, is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.
The Octart was a versatile serial subsystem. Under program control, it could switch its internal memory configuration from 16 KB bytes of ROM and 32 KB bytes of RAM to a full 64 KB bytes of RAM.
Thus the board can include a ROM bootstrap program which loads an application program, and then switches to 64 KB bytes of RAM for maximum buffer space. The eight serial channels could operate independently of one another in any of four modes: full duplex, auto echo, local loopback, and remote loopback.
Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, so it is mainly used to store firmware or application software in plug-in cartridges.
Each channel could be programmed to automatic wake-up mode for multidrop applications.
The Octart required Z80 Cromix version 11.24 or later, or 68000 Cromix 20.61 or later.
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