Cromemco Dazzler
Encyclopedia
Cromemco
's Dazzler (or TV DAZZLER) was a graphics card for S-100 bus
computers. Released in 1976, it is the first commercial graphics card available for microcomputer
s. Multiple Dazzler cards could be installed in a single machine and synched together, a feature which could, with minor modification, be used to genlock
. Genlocked Dazzler cards drove ColorGraphics Weather Systems
displays that generated most of the weather imagery seen on US television in the early 1980s.
magazine, demonstrated the original Altair 8800
to Roger Melen of Stanford University
. After seeing it, Melen purchased Altair #2 for his friend Harry Garland to work with. The two built a number of add-ons for the machine, starting with an early video digitizer called the Cyclops and then moving on to the prototype Dazzler. The Dazzler was first introduced at the Homebrew Computer Club
.
Like many early microcomputer projects of the era, the Dazzler was originally announced as a self-built kit in Popular Electronics. In order to "kick start" construction, they offered kits including a circuit board and the required parts, which the user would then assemble on their own. This led to sales of completely assembled Dazzler systems, which became the only way to purchase the product some time after. Sales were so fruitful that Melen and Garland formed Cromemco to sell the Dazzler and their other Altair add-ons, selecting a name based on Crothers Memorial Hall, their residence while attending Stanford.
When Federico Faggin
's new company introduced the Z80, Cromemco branched out into their own line of Z80-based S-100 compatible computers almost immediately. Over time these became the company's primary products. Combinations of their rackmount machines and the Dazzler formed the basis of ColorGraphics Weather Systems
(CWS) product line into the late 1980s, and when CWS was purchased by Dynatech in 1987, Dynatech also purchased Cromemco to supply them.
Over time, Cromemco sold a number of games and basic graphics programs on paper tape and diskette, including Spacewar! in October 1976.
, and an RF modulator
was available for direct connection to a color TV.
The Dazzler lacked its own frame buffer, accessing the host machine's main memory using a custom DMA
controller that provided 1 Mbit/s throughput. The card read data from the computer at speeds that demanded the use of SRAM memory, as opposed to lower cost DRAM
s. Control signals and setup was sent and received using the S-100 bus's input/output "ports", normally mapped to 0E and 0F. 0E contained an 8-bit address pointing to the base of the frame buffer in main memory, while 0F was a bit-mapped control register with various setup information.
The Dazzler supported four graphics modes in total, selected by setting or clearing bits in the control register (0F) that controlled two orthogonal selections. The first selected the size of the frame buffer, either 512 bytes or 2 kB. The other selected normal or "X4" mode, the former using 4-bit nybbles packed 2 to a byte in the frame buffer to produce a 8-color image, or the later which was a higher resolution monochrome mode using 1-bits per pixel, 8 to a byte. Selecting the mode indirectly selected the resolution. In normal mode with a 512 byte buffer there would be 512 bytes × 2 pixels per byte = 1,024 pixels, arranged as a 32 by 32 pixel image. A 2 kB buffer produced a 64 by 64 pixel image, while the highest resolution used a 2 kB buffer in X4 mode to produce a 128 by 128 pixel image. In normal mode the color was selected from a fixed 8-color palette with an additional bit selecting intensity, while in X4 mode the foreground color was selected by setting three bits in the control register to turn on red, green or blue (or combinations) while a separate bit controlled the intensity.
Cromemco
Cromemco was a Mountain View, California microcomputer company known for its high-end Z80-based S-100 bus computers in the early days of the home computer revolution. The Cromemco Dazzler was the first color graphics card available for personal computers....
's Dazzler (or TV DAZZLER) was a graphics card for S-100 bus
S-100 bus
The S-100 bus or Altair bus, IEEE696-1983 , was an early computer bus designed in 1974 as a part of the Altair 8800, generally considered today to be the first personal computer...
computers. Released in 1976, it is the first commercial graphics card available for microcomputer
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s. Multiple Dazzler cards could be installed in a single machine and synched together, a feature which could, with minor modification, be used to genlock
Genlock
Genlock is a common technique where the video output of one source, or a specific reference signal from a signal generator, is used to synchronize other television picture sources together. The aim in video and digital audio applications is to ensure the coincidence of signals in time at a...
. Genlocked Dazzler cards drove ColorGraphics Weather Systems
ColorGraphics Weather Systems
ColorGraphics Weather Systems was a computer graphics company that pioneered the use of computer graphics for displaying weather forecasts on local television...
displays that generated most of the weather imagery seen on US television in the early 1980s.
History
The Dazzler came about in a roundabout fashion after Les Solomon, an editor for Popular ElectronicsPopular Electronics
Popular Electronics was an American magazine started by Ziff-Davis Publishing in October 1954 for electronics hobbyists and experimenters. It soon became the "World's Largest-Selling Electronics Magazine". The circulation was 240,151 in April 1957 and 400,000 by 1963. Ziff-Davis published Popular...
magazine, demonstrated the original Altair 8800
Altair 8800
The MITS Altair 8800 was a microcomputer design from 1975 based on the Intel 8080 CPU and sold by mail order through advertisements in Popular Electronics, Radio-Electronics and other hobbyist magazines. The designers hoped to sell only a few hundred build-it-yourself kits to hobbyists, and were...
to Roger Melen of Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
. After seeing it, Melen purchased Altair #2 for his friend Harry Garland to work with. The two built a number of add-ons for the machine, starting with an early video digitizer called the Cyclops and then moving on to the prototype Dazzler. The Dazzler was first introduced at the Homebrew Computer Club
Homebrew Computer Club
The Homebrew Computer Club was an early computer hobbyist users' group in Silicon Valley, which met from March 5, 1975 to December 1986...
.
Like many early microcomputer projects of the era, the Dazzler was originally announced as a self-built kit in Popular Electronics. In order to "kick start" construction, they offered kits including a circuit board and the required parts, which the user would then assemble on their own. This led to sales of completely assembled Dazzler systems, which became the only way to purchase the product some time after. Sales were so fruitful that Melen and Garland formed Cromemco to sell the Dazzler and their other Altair add-ons, selecting a name based on Crothers Memorial Hall, their residence while attending Stanford.
When Federico Faggin
Federico Faggin
Federico Faggin , who received in 2010 the National Medal of Technology and Innovation by Barack Obama, the highest honor bestowed by the United States government on scientists, engineers, and inventors, at the White House in Washington, is an Italian-born and naturalized U.S...
's new company introduced the Z80, Cromemco branched out into their own line of Z80-based S-100 compatible computers almost immediately. Over time these became the company's primary products. Combinations of their rackmount machines and the Dazzler formed the basis of ColorGraphics Weather Systems
ColorGraphics Weather Systems
ColorGraphics Weather Systems was a computer graphics company that pioneered the use of computer graphics for displaying weather forecasts on local television...
(CWS) product line into the late 1980s, and when CWS was purchased by Dynatech in 1987, Dynatech also purchased Cromemco to supply them.
Over time, Cromemco sold a number of games and basic graphics programs on paper tape and diskette, including Spacewar! in October 1976.
Description
The Dazzler used over 70 MOS and TTL IC's, which required two cards to hold all the chips, "Board 1" held the analog circuits, while "Board 2" held the bus interface and digital logic. The two cards were connected together with a 16-conductor ribbon cable. Although the analog card did not talk on the bus, it would normally be plugged into the bus for power connections and physical support within the chassis. The manual also described a way to "piggyback" the two cards with a separate power cable to save a slot. Output from the analog card was composite colorComposite video
Composite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
, and an RF modulator
RF modulator
An RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
was available for direct connection to a color TV.
The Dazzler lacked its own frame buffer, accessing the host machine's main memory using a custom DMA
Direct memory access
Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
controller that provided 1 Mbit/s throughput. The card read data from the computer at speeds that demanded the use of SRAM memory, as opposed to lower cost DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
s. Control signals and setup was sent and received using the S-100 bus's input/output "ports", normally mapped to 0E and 0F. 0E contained an 8-bit address pointing to the base of the frame buffer in main memory, while 0F was a bit-mapped control register with various setup information.
The Dazzler supported four graphics modes in total, selected by setting or clearing bits in the control register (0F) that controlled two orthogonal selections. The first selected the size of the frame buffer, either 512 bytes or 2 kB. The other selected normal or "X4" mode, the former using 4-bit nybbles packed 2 to a byte in the frame buffer to produce a 8-color image, or the later which was a higher resolution monochrome mode using 1-bits per pixel, 8 to a byte. Selecting the mode indirectly selected the resolution. In normal mode with a 512 byte buffer there would be 512 bytes × 2 pixels per byte = 1,024 pixels, arranged as a 32 by 32 pixel image. A 2 kB buffer produced a 64 by 64 pixel image, while the highest resolution used a 2 kB buffer in X4 mode to produce a 128 by 128 pixel image. In normal mode the color was selected from a fixed 8-color palette with an additional bit selecting intensity, while in X4 mode the foreground color was selected by setting three bits in the control register to turn on red, green or blue (or combinations) while a separate bit controlled the intensity.
See also
- MicroAngeloMicroAngeloSCION's MicroAngelo was an early graphics card for S-100 bus computers. Each MicroAngelo board produced a 512 by 480 pixel monochrome image, high resolution for the era.Most home computers of the era displayed 256 to 320 by 192 to 240, while the Cromemco Dazzler for S-100 machines produced only 128...
, a higher-resolution system for S-100 computers - MatroxMatroxMatrox is a producer of video card components and equipment for personal computers. Based in Dorval, Quebec, Canada it was founded by Lorne Trottier and Branko Matić....
, Matrox's first graphics product was a video card for S-100 machines, the ALT-256
External links
- Saga of a System - David Ahl's story of how he got his Altair 8800/Dazzler system built, includes some sample images
- Cromemco Dazzler, image of the original design and its instruction manual