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This site is about  retro computing, especially the SBC with homebrew extensions.

A SBC, short for Single Board Computer can be defined as a computer system, based on a microprocessor, on one printed circuit, with keyboard and display, programmable I/O ports, expansion connectors and without a casing. The 'operating system' is stored in a (EP)ROM, an often small amount of RAM is avalable to store programs and data These were the first microprocessor based computers with affordable prices for hobbyists in the late seventies of the previous century.For professionals a way of getting acquanted with the new hardware and learning the basics of programming at a (very!) low level.

Though it is a complete computer, it has a CPU, memory and I/O, it is also a very limited one. The I/O is often not more than a small keybaord with hexadecimal functions. The display is often not more than 6 or 8 seven segment LED displays, just enough to show, in hexadecimal format, addresses and data. The operating system allows entering and examining of data in memory locations, and start and stop a program. Loading and saving data is limited to either papertape readers and punches, quite common in these days, or via some modulation as datafiles on audio cassette recorders. Also common is the ability to attach a teletype like the ASR33.

A good example of such a SBC is the KIM-1, shown below. 2K ROM, 1K RAM, many I/O lines free,  six LED displays and a keyboard with hexadecimal keys and some function keys.

Why these SBC's like the KIM-1 became so popular? One reason was the low price ($ 280 for a KIM-1, I paid 795 guilders ), so it was in the price range of the average student and hobbyist. Another is the openess of design, the complete hardware description and detailed listing of the ROM. And it was not the frightening computer, but more a programmable piece of hardware. BEcuase it was so easy accessible, adding and changing the hardware is not so hard also. Programming was not easy, but editors/assemblers that could run with some added hardware like RAM and a video terminal made that possible.  

Besides playing with the SBC, to learn what the microprocessor is capable of, many SBC's were put to work as a sort of PLC, controlling devices in the real world.

What changed the popularity of SBC's was the wish to transfer it to a computer with a better user interface, like graphics on a video screen, a fullblown keyboard, a real operating system with mass storage such as floppy drives, and a higher fun factor, a.k.a. games. Or to make it a serious computer fit for business. So SBC's became extinct fast in the hobby world when the hobbycomputer appeared on the market, like the TRS-80, PET and later the C-64, MSX etc. Even later the boring business PC killed the hobbycomputer, but that is another story.

Specialized on the 6502 and Z80 SBC (Single Board Computer), small computers based on an 8 bit microprocessor. Good for learning about digital electronics and programming at a lower level. And for many the start of their career in computer science.

SBC featured here are systems like KIM-1, Apple 1 and equivalent boards like the A-ONE, Apple 1 Replica, Micro-KIM, Elektor Junior, AIM-65, SYM-1 and such.

Z80 boards include the MicroProfessor 1b.

Please visit the forum and contribute to this fascinating hobby!