[theme : Software] [author : Nico]
[theme : Mass Storage Systems] [author : Welles]
[theme : Human Interfaces] [author : Douds]
[theme : Mass Storage] [author : Lomax]
[theme : Hardware] [author : Hoegerl]
[theme : Systems Software] [author : Howerton]
[theme : Hardware] [author : Rampil-Bremeir]
[theme : Visual Perception Tricks] [author : Bain]
[theme : Systems Software] [author : Murphy]
[theme : Applications] [author : Burhans]
[theme : Processors] [author : Baker]
[theme : Software] [author : Rathkey]
[theme : Hardware] [author : Tomalelsky]
The computer was created to free mankind from the drudgery of doing tiresome chores best left to an auto- maton. In most computers, there is an extremely helpful monitor program such as the SYS 8 program available in versions by IMSAI and Processor Technology. Sometimes, the writers of such programs leave the user with a few residual chores to do, like entering line numbers for each command or operation. Bill Nico wasn't satisfied with that, and proceeded to patch in an automatic line numbering feature for SYS 8, described in his article on Sweet Auto Line.
A key component of a usable system concept is the mass storage subsystem. In this issue, Jack Breimeir, one of the engineers on the Phi-Deck design, and Ira Rampil of the University of Wisconsin begin a two part article on The Digital Cassette Subsystem. In part 1 you'll find some background information on digital recording, and details of the problem of head interface electronics for digital recording.
Mass storage is the critically important component of a personal computing system which is often passed up on grounds of price or complexity. People tend to have preconceived ideas that a controller which is a complicated technological nightmare will double the price of a drive alone. However, demonstrations of accomplishment arc a way to dispel preconceived biases. Dr Kenneth B Welles shows in his article on the Economy Floppy Interface that buying just a couple of drives and building a relatively inexpensive homebrew controller can give anyone the advantages of over 200 K bytes on line per drive. His circuit takes just 17 common integrated circuits (one of which is an LSI communications processing device).
Color television interfaces are starting to become popular. However, not everyone has a color television sitting around idly. Is it possible to have a color terminal and not have to use a color television set? Subjective color is a possibility that is explored by Steve Bain in his article Color Displays on Black and White Television Sets. Read Steve's article and find out how you too may be able to add a color modulation effect to a black and white television set.
Serial storage media are widely used in low cost computer systems. They range in performance from paper tape through cassette tapes with manual controls to high performance programmably controlled cassettes, tape cartridge drives and full industry standard magnetic tape drives. Find out some of the background information pertinent to use of most magnetic tape serial media in Brian D Murphy's article, Serial Storage Media: An Introduction and Glossary.
Human interactions with computers go both ways. For computer outputs, most people think in terms of visual displays. This completely ignores the use of other senses like hearing (or touch or smell for that matter). In Audible Interrupts for Humans, Charles F Douds describes a simple circuit which can lake advantage of the audio channel of the human system.
Here you are, a novice or experienced flier, cruising along in your ancient Cub under VFR conditions when ... all of a sudden, VFR becomes IFR and you can't see. If you had an inexpensive Omega navigation system in a portable package in your copilot's seat, you'd at least know where you are on the map with an accuracy of about I mile. In his article Cub 54, Where Are You? (Or How to Navigate Using Mini-O), Ralph Burhans begins a multiple article discussion on Omega navigation, design of an Omega receiver for use with a small computer as a personal navigation system, and software for determination of position information. Aviation enthusiasts and boating enthusiasts who are into microcomputers will be able to use this information to help make an experimental robot navigator.
Is it an impossible dream? Is it conceivable to make an audio cassette 10 port with only a single bit line in each direction? Well, if you ignore the need for connecting wires, clipping diodes and isolation capacitors, then you can use a "hardwareless" software technique such as that described in Daniel Lomax's The Impossible Dream Cassette Interface.
Most of today's microprocessors have all of their functions centralized without a single device. The F8 microprocessor by Fairchild Semiconductor is unique in that it divides the system functions among several basic circuits. In his article, Microprocessor Update: The F8 System, Robert Baker describes this rather unique way of approaching the development of a microprocessor system.
Upon receiving that first microprocessor, the budding computer hobbyist is often confronted with disdainful stares and must endure such comments as, "Well now, let's see it do something." If you have a Motorola 6800 based system with MIKBUG, John Rathkey's article, A MIKBUG Roadmap ..., will aid you in getting your system to "do something" that will satisfy even the most doubting of your critics.
In several manufactured products which have been appearing lately, a hexadecimal input keyboard is one feature of the computer processor. Joseph Hoegerl describes how this sort of Calculator Keyboard Input for the Microcomputer can be wired up and used to replace toggle switches. His version is for an 8008 system, but the same hardware is applicable to other computers as well.
If you are interested in designing your own TTL circuits you should be aware that there is a definite limit to the number of gates that can be interconnected. In TTL Loading Considerations Greg
Tomalesky explains how these limits are determined by circuit designers and gives advice on what pitfalls to watch out for when designing your own TTL circuits.
Charles Howerton has come up with an interesting and lightly coded package of 8080 routines lo perform utility functions for applications software. The design goals of filling into 256 bytes yet providing a wealth of extensions to the machine's instruction set are well met, as can be seen from his article's documentation of the package.