Anniversaries and waveform glitches share attributes of sneaking past when you don't pay attention, only becoming evident when you try to figure out what happened.
For example, 2004 marked the 30th anniversary of "Build the Mark-8 . . .Your Personal Minicomputer." Written by Jon Titus, former editor of and current contributor to Test & Measurement World and in my opinion one of microcomputing's too-often overlooked pioneers, the article appeared in Radio-Electronics magazine's July 1974 issue and described what's arguably the first expandable microcomputer.
Popular Electronics magazine for December 1975 featured a cover story written by Ed Roberts, founder of Micro Instrumentation and Telemetry Systems (MITS). Roberts' company, a struggling model-rocket accessory manufacturer, offered the Altair 8800 microcomputer as a kit. A casual observer would immediately note its similarities to a minicomputer—front-panel data-entry switches, lots of status indicator lights, and an internal expansion bus enabling custom configurations.
The Altair's S-100 bus offered a cheap alternative to minicomputers and an open architecture that encouraged design of specialty boards aimed at data-acquisition and test markets. Although primitive by today's standards, S-100 boards found their way into everything from experimental agricultural-machine controls to automated cash dispensers, and inspired today's PC-based test, measurement, and control industry.
Using surface-mount components, you could shrink the functions contained on a 5.27-by-10-in. S-100 board—or an entire S-100 system—to fit onto a business card.
Nowadays, S-100 systems are history and PCs rule the market. Shrinkage continues, and truly tiny PCs are becoming available. For years to come, existing investments in support software and low-cost hardware will keep PCs in test applications.
Beyond that, I envision ad hoc test systems assembled from domino-sized wireless data-acquisition "points," all chirping away like crickets in a woodpile and relaying data to each other and a central host and datalogging system.
And over coffee, an engineer will say, "Hey, think what we could do if we put a bunch of these little guys on a 5-by-10-in. circuit board. . . ."
What's an S-100 bus?Brad ThompsonPut simply, an S-100 bus is a printed-circuit parallel-trace backplane populated with 100-pin edge connectors selected from a surplus catalog. In the mid-1970s, expensive switched-mode power supplies drove designers to use massive iron-core transformers and unregulated power supplies. Distributing filtered DC allowed point-of-use regulation on individual S-100 boards and helped distribute the thermal load.Bus signals included address and data lines, a clock, and assorted interface and control signals derived from the processor's I/O pins. The bus suffered from timing incompatibilities that often made system integration more a matter of luck than design. Manufacturers wrangled over standardization, but eventual agreement earned the bus designation as IEEE 696.An S-100 system typically consisted of a CPU board sporting either an Intel 8080 or Zilog Z-80 microprocessor, one or more static memory boards, and one or more I/O boards. Mass storage began with perforated paper tapes and progressed to audio frequency-shift keyed (AFSK) cassette tapes and 5.25- or 8-in. floppy disks, and eventually, 5- and 10-Mbyte (megabyte!) hard-disk drives. User I/O consisted of a Teletype machine, a monochrome video board, or a serial-interface CRT data terminal.As with hardware, S-100 system software followed a "let a hundred flowers bloom" philosophy, and even Microsoft's landmark CP/M operating system suffered from incompatibilities. High-performance control applications relied heavily on assembly-language routines.For a history of the Mark-8 and Jon Titus' narrative of its origin: www.his.com/%7ejlewczyk/mark8.html For more S-100/IEEE696 bus history: www.hartetechnologies.com/manuals/ A PC on a chip? Not quite, but close: www.zfmicro.com/zfx86.html This PC fits onto a pancake: www.viamainboards.com/product/epia_mini_itx_spec.jsp?motherboardId=21