Xerox 820
Encyclopedia
The Xerox 820 was an 8-bit
desktop computer
sold by Xerox
in the early 1980s. The computer ran under the CP/M
operating system and used floppy disk
drives for mass storage. The microprocessor board was a licensed variant of the Big Board computer.
Z80 processor clocked at 2.5 MHz, and had 64 kiB of RAM
.
Hardware: The processor board was located inside the CRT unit, and included the Z80A, 64K of RAM (with optional expansion up to 32-34K), and 6-8K of ROM (expandable).
Screen: The display was a 24-line, 80-character (7x10 dot matrix) white-on-black monochrome CRT
, with software-selectable variations such as reverse video
, blinking, low-intensity (equivalent to grey text), and 4x4-resolution graphics.
Communication ports These included two 25-pin RS-232
serial ports (including one intended for a Xerox 620 or 630 printer or compatible), and two optional parallel ports which could be added via an internal pin header, usable with a Xerox-supplied or other cable.
Keyboard: A bulky 96-character ASCII keyboard with a 10-key numeric keypad and a cursor diamond which otherwise defaulted to Ctrl-A to Ctrl-D. It also included "Help" and "Line Feed" keys, and was attached to the back of the CRT unit by a thick cable.
Software: A typical 820-II came with the CP/M
2.2 operating system
, a diagnostic disk, a copy of WordStar
word processor
software, and Microsoft
's BASIC-80 computer language.
Reference: 820-II Operation Manual
: the system monitor
in ROM
allowed, at boot-up, a variety of uses via one-letter commands followed by attributes.
A user would normally use the "(L)oad" command to load a bootstrap loader (i.e., for CP/M) from a floppy or the fixed disk. One could also access a "(T)ypewriter" mode for direct interface with the serial printer port and basic typing on screen. "(H)ost terminal" would allow the 820-II to interface as a terminal via either of the serial ports, as specified, at up to 19.2 kbit/s.
For low-end system operations, however, a user could manually read or write to memory, execute code at a particular location in memory, read from or write to the system ports, or even read a sector from a disk. Further, (documented) calls to BOS subroutines allowed a skilled user or program to restart the system, perform disk operations, take keyboard input, write to the display, et al.
Reference: 820-II Reference Guide
, which could be booted jointly or separately. The operating system was 8-bit CP/M
80 and 16-bit CP/M 86, and it was supplied with the Word Perfect word processor and dBase II database management system
. It had double 8" floppy disk drives, a 12" monochrome monitor and a daisywheel printer. Later in 1984 double 5.25 floppy disk drives, a portrait-size blue monitor, and a laser printer
were offered.
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
desktop computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
sold by Xerox
Xerox
Xerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...
in the early 1980s. The computer ran under the CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
operating system and used floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
drives for mass storage. The microprocessor board was a licensed variant of the Big Board computer.
The original 820
The original Xerox 820 used a ZilogZilog
Zilog, Inc., previously known as ZiLOG , is a manufacturer of 8-bit and 24-bit microcontrollers, and is most famous for its Intel 8080-compatible Z80 series.-History:...
Z80 processor clocked at 2.5 MHz, and had 64 kiB of RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
.
Overview
The Xerox 820-II followed in 1982, featuring a Z80A processor clocked at 4.0 MHz. Pricing started at $3000.Hardware: The processor board was located inside the CRT unit, and included the Z80A, 64K of RAM (with optional expansion up to 32-34K), and 6-8K of ROM (expandable).
Screen: The display was a 24-line, 80-character (7x10 dot matrix) white-on-black monochrome CRT
CRT
-Medicine:* Capillary refill time, the rate at with blood refills empty capillaries* Cognitive Retention Therapy, a dementia treatment* Cardiac resynchronization therapy, a treatment for heart failure** CRT-D, an implanted cardiac resynchronization device...
, with software-selectable variations such as reverse video
Reverse video
Reverse video is a computer display technique whereby the background and text colour values are inverted. On older computers, displays were usually configured to display white text on a black background by default. For emphasis, one swapped the color scheme to bright background with dark text...
, blinking, low-intensity (equivalent to grey text), and 4x4-resolution graphics.
Communication ports These included two 25-pin RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
serial ports (including one intended for a Xerox 620 or 630 printer or compatible), and two optional parallel ports which could be added via an internal pin header, usable with a Xerox-supplied or other cable.
Keyboard: A bulky 96-character ASCII keyboard with a 10-key numeric keypad and a cursor diamond which otherwise defaulted to Ctrl-A to Ctrl-D. It also included "Help" and "Line Feed" keys, and was attached to the back of the CRT unit by a thick cable.
Software: A typical 820-II came with the CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
2.2 operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, a diagnostic disk, a copy of WordStar
WordStar
WordStar is a word processor application, published by MicroPro International, originally written for the CP/M operating system but later ported to DOS, that enjoyed a dominant market share during the early to mid-1980s. Although Seymour I...
word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
software, and Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's BASIC-80 computer language.
Disk storage
The CRT unit contained the processor, and a large port on the back connected via heavy cable to a disk drive, allowing a wide variety of configurations. Disk drives could be daisy-chained via a port on the back.| Component | Capacity | Tracks/disk | Sectors/track | Bytes/sector | Notes |
|---|---|---|---|---|---|
| Dual 5.25" single-sided floppy drives | 81K usable single density, 155K double density | 40 | 18 or 17 | 128 or 256 | All floppy disks are soft-sectored |
| Dual 5.25" double-sided Double-sided disk In computer science, a double-sided disk is a disk of which both sides are used to store data.Early floppy disks only used one surface for recording. The term "single sided disk" was not common until the introduction of double-sided disks, which offered double the capacity in the same physical size... floppy drives |
172K usable SD, 322K DD | 80 | 18 or 17 | 128 or 256 | |
| Dual 8" single-sided floppy drives | 241K usable SD, 482K DD | 77 | 26 | 128 or 256 | |
| Dual 8" double-sided floppy drives | 490K usable SD, 980K DD | 154 | 26 | 128 or 256 | |
| 8" rigid disk drive Hard disk A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the... |
8.19MB Megabyte The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000... |
1024 | 32 | 256 | Provided with an 8" double-sided floppy drive |
Reference: 820-II Operation Manual
The Basic Operating System (BOS) monitor
The system could function to a limited extent without having to load a disk operating systemDisk operating system
Disk Operating System and disk operating system , most often abbreviated as DOS, refers to an operating system software used in most computers that provides the abstraction and management of secondary storage devices and the information on them...
: the system monitor
System monitor
A system monitor is a hardware- or software- based system used to monitor resources and performance in a computer system.Software monitors occur more commonly, sometimes as a part of a widget engine. These monitoring systems are often used to keep track of system resources, such as CPU usage and...
in ROM
Rom
ROM, Rom, or rom is an abbreviation and name that may refer to:-In computers and mathematics:* Read-only memory, a type of storage media which is used in computers and other electronic devices....
allowed, at boot-up, a variety of uses via one-letter commands followed by attributes.
A user would normally use the "(L)oad" command to load a bootstrap loader (i.e., for CP/M) from a floppy or the fixed disk. One could also access a "(T)ypewriter" mode for direct interface with the serial printer port and basic typing on screen. "(H)ost terminal" would allow the 820-II to interface as a terminal via either of the serial ports, as specified, at up to 19.2 kbit/s.
For low-end system operations, however, a user could manually read or write to memory, execute code at a particular location in memory, read from or write to the system ports, or even read a sector from a disk. Further, (documented) calls to BOS subroutines allowed a skilled user or program to restart the system, perform disk operations, take keyboard input, write to the display, et al.
Reference: 820-II Reference Guide
Model 16/8
An updated version of this computer called the model 16/8 ran dual CPUs, an 8-bit Z80 and 16-bit Intel 8086Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...
, which could be booted jointly or separately. The operating system was 8-bit CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
80 and 16-bit CP/M 86, and it was supplied with the Word Perfect word processor and dBase II database management system
Database management system
A database management system is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators and other specialists. A database is an integrated...
. It had double 8" floppy disk drives, a 12" monochrome monitor and a daisywheel printer. Later in 1984 double 5.25 floppy disk drives, a portrait-size blue monitor, and a laser printer
Laser printer
A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers , laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced...
were offered.