Southwest Technical
Products Corporation
Model:SwTPC S/09
Price:US $3245 assembled
CPU:Motorola 6809 @ 2MHz
Memory:128K RAM
Interface:video terminal, TTY
Expansion:SS-50 bus card-cage
Storage:floppy drive(s)
cassette tape
Ports:2 serial, 1 parallel

S/09 The Mighty Micro

MC6809 Processor - 20-bit address bus
Directly addresses up to 768K of RAM

Performance and capabilities never before possible are now available to you in the SwTPC/09 Computer System. The S/09 uses the Motorola MC6809 processor, the most powerful 8-bit general purpose MPU available. It features more addressing modes than other 8-bit MPU's and an optimized consistent instruction set enhanced by powerful 16-bit instructions. This, plus 24 indexing submodes, promote the use of modern programming techniques like position independent code, re-entrancy and recursion.

The 20-bit address bus makes possible direct addressing of up to 768 K of memory without any slow or clumsy processes such as bank switching. RAM memory is designed with independent control and array cards for economical expansion of memory. The DMA and the processor boards can access memory independently for different tasks.

Multiuser capability is "built-in". No additional hardware is required to operate additional terminals. A dynamic memory management system can allocate available RAM in as small as 4 K blocks to the various users or tasks.

The dual-bus motherboard design used in the S/09 makes adding I/O ports to the system quick and economical. I/O address decoding for all I/O slots is supplied with the system. All serial I/O cards may be quickly programmed to run at standard baud rates from 110 to 38,400.

Both multiuser and multitasking/ multiuser operating systems are available for the S/09, BASIC, PASCAL and an Assembler are immediately available. Editor and Debug programs are also available for use in system development.

(Source: SwTPC advertisement)

SwTPC was originally an electronics supply company, selling power supplies, inexpensive video displays, and electronics kits to hobbyists.

After computer chips became popular, they solds those as well, eventually creating and selling their own line of computers.

Three major system were released:
  • 1975 - SwTPC 6800, with the Motorola 6800 CPU.
  • 1979 - SwTPC 69/A and the
  • 1979 - SwTPC S/09, both using the Motorola 6809 CPU.

  • The 69/A and the S/09 (seen here) were identical on the outside, but had different motherboards and hardware configurations.

    Instead of using the S-100 bus which had become standard on many other computers, SwTPC utilized their own bus, the SS-50 bus, as seen above, with only 50 connections instead of 100. Electronic technicians will recognize these as Molex connectors.

    Because of this, the motherboard was "male", and the expansion cards were "female", opposite that of the S-100 bus.

    The S/09 motherboard actually has two separate buses, the SS-50 and a smaller SS-30, for different size expansion cards.

    This is exceptionally convenient - it allows twice as many cards to be installed, and small and simple cards do not take up an entire full-size expansion "slot".

    Just as nice, the small cards pass-through the back of the system, as seen below, allowing additional ports and features to be easily added.

    Related Links

  • SwTPC S/09 Computer System and S/09 The Mighty Micro from
  • SwTPC S/09 from ""

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