Early S-100: My First Computer's Evolution
I planned to buy an Altair or Imsai in early 1977 but as I did product research the Cromemco product seemed better. After buying an 8K memory card (4Mhz capable) on sale for $228, I bought a Z-2 chassis kit with their 4Mhz ZPU for about $650?. I wanted the best pixelated graphics so bought a Mini-Term Associates, MERLIN graphics/display board (kit) with the super graphics daughter card that gave me 300x200 pixels black and white. I bought an electronic keyboard and made a parallel interface to the ZPU on a Radio Shack project board. My display was a Hitachi B&W portable TV with a Pickles&Trout converter (toggle a switch for TV or Computer).
The advantage of the MERLIN is that you didn't need a front panel. The ZPU booted to the MERLIN monitor code and it would allow direct entry into memory by HEX. That was a *big* advantage at the time. I wrote assembly language programs on paper and hand assembled them with my Z80-CPU Technical Handbook and wrote the resulting address and data in hex on notebook paper. I used entry points in the MERLIN monitor for handy routines and display settings. I have high praise for the MERLIN.
To play a game I wrote, like BATTLESHIP, I'd pull the page out of my notebook with the machine code written out, and then I'd spend about 10 minutes entering the program by HEX before playing. I bought a Kansas City Cassette Tape interface from Mini-term and their best graphics based space ship game like you'd find in video arcades. The better game came free with the KC board, called Piranha - graphics based, you swam back and forth across a swimming pool avoiding piranhas with various speed and hunger. I didn't consider using cassette tapes worth the bother.
I bought a EPROM programmer board to avoid re-entering my useful programs. I bought a NorthStar MDS board kit and that made data handling a lot easier. I bought a Paper Tiger Impact Printer with graphics capability, and more memory cards as the prices dropped.
I wirewrapped my own programmable sound generator S-100 board using the General Instruments AY3-8910. That was a lot of fun because the sound effects you could create were incredible. I wrote a program to do piano keyboard from the QWERTY keyboard but found that useless. I had more success writing a program that would read and play a datafile I created from sheet music; I have no music talent - this was just entertaining data to me.
I bought TP/M which was a cheap CP/M system and didn't think much of it. It offered an assembler but the NorthStar floppy was one drive and little capacity. I stuck with NS's OS and the MERLIN monitor.
After reading the BYTE magazine article introducing CBBS and the concept of having BBSs, I bought a D.C.Hayes Micromodem 100 (assembled) and had to write my own Z80 interface, then write a modem program and burned it into EPROM. At the time there were only about three BBS's in Dallas Tx.
My senior year at SMU's electrical engineering school, I used my S-100 modem programs to avoided the long, late-night lines for the punch card machines at the computer center; they stayed open to 4AM. First I scanned through the wall of CDC manuals looking for a dial-up access number - no luck. Then I programmed my S-100 to dial all the possible numbers in the computer center's phone exchange late night on the weekend until I found a carrier. Success! With that I entered my data structure's final project and debugged it from the comfort of my apartment. After all, college is supposed to teach students to work smarter.
When I saw the movie WARGAMES years later, during several scenes I said... "Been There... Done that..."
I planned to buy an Altair or Imsai in early 1977 but as I did product research the Cromemco product seemed better. After buying an 8K memory card (4Mhz capable) on sale for $228, I bought a Z-2 chassis kit with their 4Mhz ZPU for about $650?. I wanted the best pixelated graphics so bought a Mini-Term Associates, MERLIN graphics/display board (kit) with the super graphics daughter card that gave me 300x200 pixels black and white. I bought an electronic keyboard and made a parallel interface to the ZPU on a Radio Shack project board. My display was a Hitachi B&W portable TV with a Pickles&Trout converter (toggle a switch for TV or Computer).
The advantage of the MERLIN is that you didn't need a front panel. The ZPU booted to the MERLIN monitor code and it would allow direct entry into memory by HEX. That was a *big* advantage at the time. I wrote assembly language programs on paper and hand assembled them with my Z80-CPU Technical Handbook and wrote the resulting address and data in hex on notebook paper. I used entry points in the MERLIN monitor for handy routines and display settings. I have high praise for the MERLIN.
To play a game I wrote, like BATTLESHIP, I'd pull the page out of my notebook with the machine code written out, and then I'd spend about 10 minutes entering the program by HEX before playing. I bought a Kansas City Cassette Tape interface from Mini-term and their best graphics based space ship game like you'd find in video arcades. The better game came free with the KC board, called Piranha - graphics based, you swam back and forth across a swimming pool avoiding piranhas with various speed and hunger. I didn't consider using cassette tapes worth the bother.
I bought a EPROM programmer board to avoid re-entering my useful programs. I bought a NorthStar MDS board kit and that made data handling a lot easier. I bought a Paper Tiger Impact Printer with graphics capability, and more memory cards as the prices dropped.
I wirewrapped my own programmable sound generator S-100 board using the General Instruments AY3-8910. That was a lot of fun because the sound effects you could create were incredible. I wrote a program to do piano keyboard from the QWERTY keyboard but found that useless. I had more success writing a program that would read and play a datafile I created from sheet music; I have no music talent - this was just entertaining data to me.
I bought TP/M which was a cheap CP/M system and didn't think much of it. It offered an assembler but the NorthStar floppy was one drive and little capacity. I stuck with NS's OS and the MERLIN monitor.
After reading the BYTE magazine article introducing CBBS and the concept of having BBSs, I bought a D.C.Hayes Micromodem 100 (assembled) and had to write my own Z80 interface, then write a modem program and burned it into EPROM. At the time there were only about three BBS's in Dallas Tx.
My senior year at SMU's electrical engineering school, I used my S-100 modem programs to avoided the long, late-night lines for the punch card machines at the computer center; they stayed open to 4AM. First I scanned through the wall of CDC manuals looking for a dial-up access number - no luck. Then I programmed my S-100 to dial all the possible numbers in the computer center's phone exchange late night on the weekend until I found a carrier. Success! With that I entered my data structure's final project and debugged it from the comfort of my apartment. After all, college is supposed to teach students to work smarter.
When I saw the movie WARGAMES years later, during several scenes I said... "Been There... Done that..."
Last edited: