Wayne Green's Visit to SWTPC

The visit was in early August 1975 and was published in the February 1976 issue of 73 Magazine. This is an expanded version of his article in the October 1975 issues of BYTE and 73 magazines (Photos below)

SWT
The third stop on my microprocessor tour was Southwest Technical Products in San Antonio. Actually this was just a very lucky coincidence, for I went there to see them in regard to their television typewriter unit which is a natural to go with computer systems as well as amateur teletype.

Dan Meyer, the president, and Gary Kay, the chief engineer, spent the day showing me their new 6800-based microcomputer system which is due to be released soon in kit form. They had a prototype system set up and working and it certainly was impressive. I asked a lot of questions, trying not to make my abysmal ignorance of microprocessors too evident.

For instance, I asked how come they went with the 6800 chip for their system instead of the several others available.

8080 vs 6800
While I figure it will be quite a while before the proponents of each chip will be cool enough to sit down and work out a comparative evaluation of the situation, this has not stopped me from asking the participants to give me their reasons for going one route or the other.

Gary Kay, the computer engineering brains at Southwest Tech, tried to explain the differences between the two chips to me and why he decided to go with the Motorola 6800. I understood things here and there, aware of a need for a better interface for dealing with people who speak in computerese.

Well, it seems that Gary looked into everything available ... went to courses provided by the chip manufacturers ... read a lot ... and it all came down to the 6800 for him. It was much easier to interface than the 8080 ... required fewer external parts since much of the work is done by software instead of hardware. This need for fewer parts would seem to be demonstrated by the substantially lower cost of 6800 based units vs. 8080 units (the MITS 6800 based unit is $293 vs. $439 for the 8080 kit).

With the 6800 you can set up any of the 16 lines for input or output and change anytime you want just by programming instructions .. . even in the middle of a program. You can program the system to give any priority for a particular input device. You can do a lot of things with programming that have to be done by switching with the 8080. You can even program whether it will work on a positive or negative strobe (if you are). The handshake line ... lets it be known when data has been received ... is all right there on the chip. The 6800 was designed as a system and thus takes less outside equipment to get it working.

Another plus is the Motorola supplied MIKBUG, a small operating system which is available on a ROM chip. This is a nice feature which can be appreciated by 8080 users who find they have to start out by hand switching in about twenty steps before the system will be able to accept programming from tape or cassettes ... or even a keyboard. Thus, with the 6800 systems you can just flick on the power switch and the initial programming is all done by the built-in read only memory and you find a snowflake blinking at you on your screen indicating the system is ready for use.

This elimination for the necessity of hand switching in the loading program has made it possible to do away with the usual computer front panel and its row of switches and rows of LEDs. Further instructions to the system can be put in by means of a keyboard using octal or hexadecimal notation, whichever has been programmed in by the ROM ... hexadecimal in the case of MIKBUG.

As time passes we will see whether the 8080 or the 6800 systems have more for the users . . . and that is the bottom line.

The Southwest Tech 6800 kit sells for $450 and includes some handy items. There is the mother board into which the processor, memory and I/O boards plug, a chassis and cover, power supply, the processor board with the 6800 chip, ROM MIKBUG, 128 bytes of RAM and a clock for the system, and a hoard with a serial input/output for teletype or RS-232 such as the CT-1204 terminal. A 4K memory board is also included which has 2K on it and space for plugging in 2K more to fill out the 4K ... the extra 2K is available for only $45. The result is that you have a complete computer system for $450.

In addition to the 6800 kit you'll need to have some sort of I/O device, probably either a teletype with ASCII output or a TV video system such as the CT-1024 kit and a TV set. You'll need more memory for any practical computer operating system . . . certainly the extra 2K and more probably a total of 8K. You will need some sort of bulk memory system such as a cassette recorder and an I/O board which will interface it to the system. Floppy disk systems are nice, but they are still too expensive for most hobby systems and the programs to operate them have yet to be written.

The Southwest Technical operation is a beauty to behold. They are using a Datapoint computer system to run the whole works. The sales are 100% mail order and each order is entered in the computer as it is received. A label and packing slip is printed out for each order and an acknowledgement sent out automatically. Each week all orders are processed by the system and inventory records updated to account for every resistor and part used in the kits. Delivery schedules are in the system too, so when parts in stock get below a quantity which might cause them to run out the computer initiates an order for the parts. Since this system was set up there have been no delays in filling orders due to out of stock parts!

Questions on orders can be quickly resolved by searching the computer memory for the name, zip, or even the ordered kit. Everything is right there at hand.

Dan Meyer, the president of Southwest Tech, took me for a tour of the plant ... it was enormous. The printing department is bigger than the 73 printery which turns out the many 73 books ... acres of space filled with shelves of parts, people putting kits together, and more cartons that you would believe. The company has built up a good name in the hi-fi field where it is one of the largest of the kit manufacturers and known for the high quality of their units.

The first excursion into ham territory was with their television typewriter kit ... a natural for RTTY operators. The CT-1024 terminal system, first made known in a nice article in Popular Electronics, consisted of a character generator, sync and timing circuits, cursor, 1024 byte memory ... all you need to put a 16 line message on the screen of a television set with a video jack on it. The 1024 byte memory is enough for two pages on the screen and the unit automatically switches from one page to the next when the bottom of a page is reached. This kit sells for $175 and is very simple to put together. My twelve year old daughter helped with a good deal of the assembly and soldering of my kit.

A power supply for the unit is available for $15.50 more, as is a keyboard for about $40 and an output interface to feed ASCII to your RTTY system or to a computer ($40). Thus, for about $275 you have a complete system, requiring only an old black and white TV set for a display and an RTTY system geared to ASCII input (RS-232). Compared to today's teletype machine prices, that has to be one of the best bargains going. Compared to commercial video display keyboards it also was an outstanding buy.

The SWTPC 6800 computer kit looks like a winner, too. Priced at $450, it includes a 714 page applications manual, the 6800 chip, the MIKBUG ROM operating system, a serial interface which will operate a 20 mA teletype or work with their TV typewriter system.