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Subsystem B
The Master's Touch

Owners of Altair, Imsai, Vector Graphic, Parasitic Engineering, Cromemco Z-2, TDL and other S-100 bus computers take heart! Discover the joys of an integrated system composed by a master.

With the exception of our own lovable Sol whose original design incorporated a systematic approach to small computer development, all S-100 bus computers demand additional hardware as well as software to get them up and on the air. Without a memory module, the computer cannot handle large amounts of data. Without input/output interfaces, it cannot receive data from a keyboard, transfer information to a tv monitor or teletype printout, or store data on a cassette. Without some elementary software routines built into the system, complex sets of preliminary routines must be entered into the computer before it can coordinate all these activities or load a simple program. In other words, a microcomputer, technological miracle though it is, cannot be useful to any human being without the help of further technological miracles.

In the past, small computer enthusiasts have pieced together their systems purchasing one component here, another there, and then found themselves strug­gling to make everything work together.

Subsystem B, a contemporary classic from Processor Technology, puts an end to all this struggle and confusion. In one package, at a remarkably low price, we have included a memory module, three input/output modules, a general purpose memory and appropriate software. For those who prefer the finest craftsmanship over a mess of parts. . . for those who want the pleasure of running and writing pro­grams without clumsy preliminaries. . .

Subsystem B offers a choice of three memory modules — 4KRA, 8KRA or 16KRA— with four, eight or sixteen thousand bytes of memory for programs and data. The VDM-1 module interfaces the computer with a tv monitor. The CUTS (the Computer Users Tape System) module interfaces with a cassette recorder for program loading and mass storage of up to 200,000 characters per C-60 cassette. For all other communica­tion to the outside world keyboard, teletype, printers and so forth — 3P+S provides three ports for data input or output.

The General Purpose Memory (GPM) is a single piece of hardware/software which integrates the functions of all the other modules. The software is preprogrammed onto IC chips and provides instructions to operate the interfaces as well as set up elementary operating commands for the system as a whole which can be entered through a keyboard.

The block diagram below shows how a system with a computer and all the Subsystem B components would look. 

The General Purpose Memory makes it all possible.

The key concept underlying Subsystem B is inherent in the software which integrates the overall functions of the hardware to create a system that is greater than the sum of its parts. Processor Technology has developed and produced this software as a program called CUTER.

CUTER ties together the internal functions of the central computer as well as a cassette recorder, key­board, video display and other peripheral equipment. It also brings standard commands to the system such as ENTER, DUMP, GET, EXECUTE and CATALOG as well as custom commands. Furthermore, CUTER makes all Processor Technology and Software Technology programs compatible with the system. CUTER has been preprogrammed in Read Only Memory integrated circuits which reside on the GPM board. It takes up 2,048 bytes of memory space. GPM also has a 1,024 byte area which is used as scratchpad.

Reserved space is available on the GPM board for later addition of a powerful ROM-resident assembler, the ALS-8. To simulate 8080 programs without running them in real time, the SIM-l interpretive simulator can also be added. For further flexibility, with SIM-1 comes our eminently useful TXT-2 text editor, designed to make file editing quick and easy.

Load programs at a new tempo with CUTS.

For those who are still loading programs via paper tape or flipping switches, CUTS will bring a new tempo to system operations. A cassette recorder with CUTS interface loads programs ten times faster than a TTY paper tape reader. Processor Technology’s BASIC-5 program, which is included with CUTS, will load in just 58 seconds. We have also included two popular computer games on this tape.

CUTS is fully compatible with the Byte/Kansas City standard; it will operate at either 300 or 1200 bits per second. Automatic Gain Control eliminates adjust­ments of the cassette recorder volume or tone controls and minimizes bit drop-out in both read and write modes.

Cassettes simplify data storage because they are compact and can be filed away indefinitely without deterioration. Information can be economically stored and then retrieved quickly.

With CUTS, all Processor Technology and Software Technology programs will run without modi­fication on any S-100 bus computer. CUTS provides the standardization which guarantees availability of an ever increasing selection of compatible software.

Harmonious video interface VDM-1.

As the original video display interface for S-100 bus systems, VDM-1 is still the most popular. It generates sixteen 64-character lines in a large, easy-to-read, upper and lower case typeface on any standard video monitor or modified tv set.

By utilizing a 1,024 byte segment of system memory, VDM-1 provides extremely fast operation. For example, any character on the screen can be accessed by the processor in microseconds.

Once the processor provides the display status parameters, the VDM-1 can scroll its display upward or downward at a top speed of about 1000 lines per minute.

The VDM-1 is versatile with fully programmable cursor positioning. It will display black-on-white or white-on-black, perfect for many video games. Software is included for terminal mode operation in addition to the CUTER program.

I/O Versatility with 3P+S.

Virtually all other input/output needs of any S-100 bus computer are handled with ease by the 3P + S module. No need to buy separate interfaces for serial and parallel devices; 3P +S has both.

The serial port has a standard RS-232 interface as well as standard current loop interface for teletypes and various printers. The data rate is selectable up to 9600 baud.

One of the parallel ports sets control conditions for the other ports as well as setting the serial I/O baud rate. Two other 8-bit parallel ports will interface a key­board or paper tape reader with full handshaking logic.

The extraordinary versatility of the 3P + S module allows it to accommodate virtually any type of peripheral with only minor modifications. The addressing is selectable to any of 64 address segments within the 8080 microprocessor’s range of 256 input/output addresses.


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