[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke, Manfred Peschke] [art : Matthew Arnorld, Noreen Bardsley, Mary Jane Frohlich, Lynn Malo, Bill Morello] [cover : Robert Tinney] #Magazine
#Abstract
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.
[author : Portia Isaacson] #Edito
Extract : « Several years ago we knew that computers were going to become very small and very inexpensive. However, predictions of the effect of inexpensive computers did not begin to cover the strength of today's personal computing movement, where we find enthusiasm at a very high pitch. It is clear that we are entering a dramatic new era in which information processing power will be abundantly available for use by the individual consumer.
The only thing one could be sure about during the past year when writing about the personal computing movement is that by the time the article was printed it would certainly be antiquated. Every month there are several new computer clubs, several new computer stores, hundreds more computers owned by individuals, and a noticeably higher level of excitement among insiders to the movement. To most of us the whole idea of personal computing is so delightfully intoxicating that we can't quite believe its time has really come — but it has! [...] »
TABLE OF CONTENTS
[theme : Software] [author : Nico] #Listing #Assembly #Algorithm #Programming
Extract : « I was writing a program the other day, using the editor and assembler provisions of the SYS 8 self-contained operating system. For the N to the ith time, I forgot to type in a new line number before entering the instruction code and got the familiar WHAT? response from the monitor program. If there was a market for WHAT?, I'd be rich! [...] »
[theme : Mass Storage Systems] [author : Welles] #Electronic #Interface #Storage #Listing #Assembly
Extract : « The floppy disk drive offers the advanced computer hobbyist tremendous potential for a high performance computer system. With one or more floppy disk drives, an interface, and the proper operating software, the hobbyist can store hundreds of different programs on a single disk. Each of the programs can be given a name such as STARTREK, BASIC or EDIT, and a program can be run simply by typing its name, for instance "RUN EDIT". With this interface, the program can be brought into the computer at speeds of up to 31,250 bytes per second (for programs less than 5000 bytes long in the proper format). Each disk will store over 300,000 bytes of programs, computer music, Dazzler graphics, ASCII text, synthesized speech thesaurus or data of any form, and any data on the disk can be accessed in at most one second, typically in less than one quarter second. [...] »
[theme : Human Interfaces] [author : Douds] #Electronic #Audio
Extract : « One of the great virtues of computers is that their flexibility allows them to do all kinds of things to make our lives easier or better.
Unfortunately, systems analysts and programmers working on big systems sometimes tend to forget this. Microprocessors can make things easier and more fun for us, too. But we sometimes forget the basic principle of human engineering: People should not be forced to fit the system; the system should fit the people. [...] »
[theme : Mass Storage] [author : Lomax] #Electronic #Interface #Storage #Listing #Assembly
Extract : « In May 1975, I had a new Altair 8800, from the original Popular Electronics offer, with 256 bytes of memory and no more money. What could I do besides blink lights? The first thing I noticed was that there is an addressable latch in the system, the Interrupt Enabled latch on the 8080, which is nicely buffered and displayed on the Altair front panel. After turning it on and off for a few hours, it occurred to me that, with an earphone, the light might make music, and, after several day's mad programming, some incredibly accurate baroque music emerged, including one recorder piece of which a musician friend — who loaded the data for it — said he had never before been able to hear, being too busy playing it. [...] »
[theme : Hardware] [author : Hoegerl] #Electronic #Interface #Keyboard #Listing #Assembly #Programming
Extract : « [...] It did not take long for me to see that entering programs by way of the front panel switches was tedious and time consuming, especially since programs quickly become more complicated and longer as programming proficiency develops. There was a need for a simpler method to put the programs into the memory. The thought occurred to me that an inexpensive and simple solution might be to adapt a calculator keyboard to enter data in octal form. [...] »
[theme : Systems Software] [author : Howerton] #Listing #Assembly #Programming
Extract : « The programming convenience of a computer system is greatly enhanced by using software to extend the functions provided by the basic instruction set of the machine. Software to accomplish complicated functions like moving character strings or doing data conversions help the user to program manipulations of data in an application situation. This article is written to describe and give the code for a set of utility routines for the 8080 which can be used to advantage on any system employing this chip. This set of BARC utility routines is designed to assist the 8080 programmer in developing programs which involve the manipulation and validation of characters and character strings. The acronym "BARC" stands for BAsic Resource Capability. Almost all programs require these functions to a greater or a lesser extent if they accept input or generate output in any format other than absolute machine codes. [...] »
[theme : Hardware] [author : Rampil-Bremeir] #Electronic #Interface #Storage
Extract : « When people first acquire a small computer of traditional design, they are usually content for some time with using the console lights and switches for IO. If the proud new owner has any software aspirations, he or she will soon begin to crave some sort of device to raise the level of intelligence of the man-machine interface. For many, an ASR 33 Teletype or its equivalent makes an ideal first peripheral for a computer system; it gives one a keyboard, a hard copy printer, and paper tape bulk storage for program libraries. There comes a time, however, when the incessant clatter of a 10 character per second paper tape reader is no longer music to one's ears. The fact of the matter seems to be that as the ambition of a programmer grows, so does that programmer's restlessness and impatience to see things being done. There is something irksome about sitting and watching one's IO machine take longer to read a program than it took to code it. The obvious answer is a high speed random access store, like a disk or drum. However, no matter how elegant it might be, not everyone has $5 K for a cartridge disk. Floppy disks are not yet the answer in terms of cost, reliability and media life. Perhaps the best answer for today's amateur may lie with the ubiquitous Philips cassette. There are many alternatives when dealing with cassettes from which to make design choices. Therefore, this article is meant as a reference for ideas, rather than as a construction article. [...] »
[theme : Visual Perception Tricks] [author : Bain] #Electronic #Interface #Display
Extract : « Interest has been growing in the idea of using standard color television receivers as microcomputer output devices. At least one color television interface is already commercially available and more are on the way. In addition, many homebrew projects are ongoing. [...] »
[theme : Systems Software] [author : Murphy] #Storage #Glossary
Extract : « This is an introduction to the use of a cassette type recorder for mass storage of information. Once the initial novelty of the small computer system has worn away, a junction occurs at which the computer freak either matures or puts his (or her) system on the market and moves on to something else like stamp collecting. [...] »
[theme : Applications] [author : Burhans] #Electronic #Transport #Glossary
Extract : « The Omega navigation system is a radio based method which was originally designed as an ocean locating system for shipping, it was not intended for use over the world land masses. However, the signals are free to the user no matter where he/she is located and in a sense represent another worldwide resource particularly for those who have no other radio navigation aid available. In continental USA urban areas, we have many VHF-UHF and microwave navigation aids for aircraft, so there is not much need for Omega except in remote mountain areas where line of sight propagation is restricted and the VLF-Omega is not disturbed. Omega in other parts of the world is often the only radio navigation aid available for planes and boats. Omega and other VLF systems arc often used by offshore oil drilling and marine exploration crews as a means of locating their rigs or vessels particularly while in transit to and from. [...] »
[theme : Processors] [author : Baker] #Review #Microprocessor
Extract : « The architecture of the F8 microprocessor is rather unique in design since the various system functions are deliberately divided among the several basic circuits of the F8 family instead of being centralized within a single processor. The currently available F8 system components include the following devices: 3850 central processing unit 3851 program storage unit 3852 dynamic memory interface 3853 static memory interface 3854 direct memory access
These devices are interconnected by an 8 bit time multiplexed data bus for addressing and data functions, along with a 7 bit control bus for system coordination and synchronization. [...] »
[theme : Software] [author : Rathkey] #Listing #Assembly
Extract : « Some of the more useful microprocessor options for hobbyists available today are based upon Motorola's MIKBUG monitor program. These options include the Motorola 6800 Design Evaluation Kit, the SWTPC 6800 computer, etc. A big attraction of such kits is the MIKBUG read only memory, which provides the user with a monitor system and includes several utility routines. [...] »
[theme : Hardware] [author : Tomalelsky] #Electronic
Extract : « If you have ever studied a microcomputer's schematic diagram, chances are you have seen gates, flip flops, memories, etc, connected together to perform certain tasks essential to the operation of the computer. Upon closer examination you should notice that various logic families are mixed, such as 74XX, 74LXX, 74LSXX and perhaps even CMOS. However, you may not have noticed that there is a limit to the number of gates that may be interconnected. The purpose of this article is to show how these limitations are arrived at by circuit designers and what you should watch out for in your own circuit design. [...] »
#Association
#Book
Extract : « How to Buy and Use Minicomputers and Microcomputers, by William Barden Jr, Howard W Sams and Co Inc, Indianapolis, 1976, 240 pages, 8-1/2 x 11, paperback, $9.95. [...] »
