M1975-1980-Change

Personal Computers and Word Processors

Collins division of Rockwell established a plan, soon followed by Autonetics, where the company enabled purchase of a Commodore computer with a pay roll deductions until the unit was paid for.  This continued for new models and accessories. This offer was very popular among engineers and I bought each offering as it became available.  Thus Collins and Autonetics engineers helped evolve early computers by providing a market and feedback.  In the beginning they were not user friendly, only engineers or dedicated hobbyists had the tenacity or incentive to stick with it. 

            The following Commodore 8K machine was the first of rapidly changing machine, the user could write instructions in Basic, command Run and the machine would interpret the Basic instructions as it ran, converting Basic to machine code for the microprocessor. 

  

1977? Commodore 2001 PET  with small keyboard, built in cassette, monitor and motherboard with 8 K of  RAM (Random Access Memory) and Basic installed in ROM (Read Only Memory) devices shown above.

This Commodore and first Apple machine came out at about the same time, both using the 8 bit 6502 microprocessor operating at 1 mhz.  The 6502 microprocessor was made by engineers who broke away from Motorola, then making the 6800 microprocessor, calling themselves MOS which was later purchased by Commodore.  Thus Apple was buying it’s microprocessors from Commodore.  One of the MOS engineers became chief Engineer for a new Microelectronics division of Autonetics, who built the 6502 microprocessor under license.  Microsoft wrote the Basic operating system software for both Commodore and Apple until Apple began defining their own code.  Commodore machines came with Microsoft Basic and stored in 7 ROM’s built into the mother board.  The 8 K of RAM was (16) 512 bit IC’s near the front of the above mother board.  The keyboard addressed a ROM Look Up Table and stored characters in a dedicated part of the 8 K RAM and displayed on a 40 character wide monitor.  The system used ASCII (American Standard Code #2) code, using 7 bit alpha-numeric and or graphic characters selected by the 8th bit with the shift key as shown below. 

Commodore small Keyboard with shift key activated Graphics characters

 

Commodore  PET 2001  16K RAM version with large keyboard and independent Cassette Memory Drive

            This still used a small 40 character wide screen.  Admiral, a large TV producer, had gone out of business and Commodore bought large quantities of their TV tubes and converted them into monitors.  Commodores cases were built like a car, with a lift up hood, to get to the mother board.  A “video board” was under the Tube as part of the lift up lid.  This version include an RS232 serial port adapted for use with an independent cassette drive. This version was also equipped with a parallel IEEE 488 external connection; an industry standard used by Hewlett Packard and others to inter connect electronics test equipment

 

Commodore Cassette tape drive

            At an Autonetics had a computer club and a meeting a member told of contacting Commodore and their implementing his recommendation for changing the RS232 single side drive to “push pull”  

            For a single sided driver the resistor and coil in series constitute a “voltage divider” with less voltage across the coil.  For a push-pull driver full battery voltage is applied across the coil providing a more positive reliable signal. 

  

Commodore  PET 2001  32 K RAM version  large 80 characters wide screen & large keyboard

            This third version quickly replaced the earlier models.

  

Commodore Dual Floppy drive   with  IEEE 488 parallel cable --  at right RS232 serial cable interface

            The Commodore Dual Floppy Disk drive used a 5 ¼” floppy, truly floppy, disks that wrote in standard density then a later model in double density.  These connected via an IEEE 488 cable edge connection on the mother board to an IEEE 488 test equipment standard connector on the Floppy Drive.  The IEEE 488 standard was used by Hewlett Packard for lab test equipment.  Not long after others came out with floppy drives which using an RS232 Serial link. 

   

The dot matrix printers worked remarkably well

1975  Rockwell  AIM 65  with 6502 microprocessor, standard keyboard, LED display, printer and serial port for cassette tape memory  BASIC on ROM with 64 meg RAM,

  

            DOS (Disc Operating System)  by Microsoft provided a better way to talk with the floppy drives.  Shugart, which became Seagate, were the first to provide desk top floppy drives.  DOS was a godsend to early users.  It’s still in use buried out of sight in Windows software retaining much of its early protocols – upgraded from 8 bit to 16 bit to 32 bit and now 64 bit code.  Microsoft was a key player in making the PC a practical and useful machine.

            DOS was soon merged with Interpretive BASIC on ROM’s.  When IBM needed something in a hurry to catch up, they contracted with Microsoft for their PC software.  Microsoft retained the rights and IBM and Microsoft made it available on floppy discs – which could be upgraded.

            Random Access Memory was a pacing development.  Initially small and expensive, desk top computers didn’t have any breathing room until 64 K minimum. 

            An outfit in Canada enhanced the Commodore 32, by adding an extra mother board with a new Motorola 68000 16 bit microprocessor. These were used to interface with IBM mainframes.  The little guys were starting to each IBM’s lunch.

 

Commodore User Manual

Commodore user manuals provided technical content unavailable from other sources at the time.  The machine was faster and more powerful if programmed in machine language.  This manual revealed a means of branching to user written code.  The manual also defined how the system was set up to run Microsoft Basic.  I studied these in great detail to determining how to implement programs written in machine code.

 

 

 

Manual’s samples of code stored in ROMs

            The above is a “disassembled” print out of ROM codes.

            From our “computer lab” I obtained an early copy of Microsoft’s “editor”, “assembler” and “dis-assembler” software on a cassette tape.  I learned how to write a program in the above format, then “assemble” it in machine code and save it to a cassette tape.  I could “disassemble” to reverse the process.  I found ways to set up “breaks” such that I could prove software up to a point.  These were do-it-yourself programming tools. 

            The Collins Division had disassembled the ROM codes and placed them is a document I checked out from the Autonetics library.  After a considerable effort I was able to write a word processor program which we used to help restart the B-1B bomber program.  There was no equivalent software available at that time.  However I first had to learn how the microprocessor worked.

IBM PC

            To play catch up IBM came up with a mother board design for which they could buy electronics from current desk top providers, placed on cards that would plug into their motherboard.  Thus an “IBM Standard” was born, initially known as ISA 16 bit slots.  The IBM PC took off like wildfire – eventually causing the downfall Commodore and truncating Apple expansion.  IBM bought a significant holding in Intel to assure they would have a microprocessor for their own IBM PC and used and advanced 5 ¼ “ floppy design calling it double density, followed by a new 3 ½ in “solid floppy” which soon made obsolete prior floppies.  As RAM became more plentiful and the IBM was equipped with 1 meg RAM as standard on the motherboard – suppliers made plug extra memory cards.  Video cards offered color – now possible with more memory.  Hard drives entered the market using the 3 ½ inch disk size – stacking them inside a sealed chamber, read by a tiny arm whose head remained airborne just above the high speed disk.

Apple to Motorola  68000

To remain in business Apple changed to the 16 bit Motorola 68000 microprocessor and specialized in software with more appeal to publishing firms.

Clones eat IBM’s lunch

The IBM machines were based on devices designed by others and soon the others built what was called clones selling for less and often doing more.  Eventually IBM got out of the PC business and focused on serving industrial data processing computer system needs.  Commodore fades out and Intel took over the microprocessor world and Microsoft Software became an international standard. 

 

I became acquainted with the Oberlin high school science teacher and provided him a copy of the above which he took with him during further graduate school studies.  He wrote back to thank me – that he and fellow students found it very helpful in their own studies and efforts.  He had been teaching Boolean Algebra, used to plan logic networks, and I’d advised him to move on and focus on microprocessors. New technology first moves by Word of Mouth.