{{unreferenced, date=June 2017 Cromemco Octart S-100 card (1983)

The Cromemco Octart was an

expansion card In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus slo ...

made by

Cromemco Cromemco was a Mountain View, California microcomputer company known for its high-end Zilog Z80, Z80-based S-100 bus computers and peripherals in the early days of the personal computer revolution. The company began as a partnership in 1974 betwe ...

for their range of

S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of ...

based computer systems. The card provided eight

serial bus In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are ...

channels and a single bi-directional

parallel port In computing, a parallel port is a type of interface found on early computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once ( parallel ...

. The serial connections were often used to interface eight

computer terminal A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...

s to the host system. In combination with the Cromemco Cromix multi-user

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

, this allowed different users to concurrently work on the system. The parallel port was typically connected to an

IEEE 1284 IEEE 1284 is a standard that defines bi-directional parallel communications between computers and other devices. It was originally developed in the 1970s by Centronics, and was widely known as the Centronics port, both before and after its IEEE ...

-type printer. 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 A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

and dramatically increased system throughput. 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 Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * Ra ...

to a full 64 KB bytes of RAM. Thus the board can include a

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * R ...

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. 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.

External links

Cromemco Octart Asynchronous Communications Processor Instruction Manual
Octart Serial buses