In this end of year 1977, when a computer fanatic wished to build himself a powerful and evolutional computer, he'd only have pactically one choice: to purchase a S-100 Bus based system, assembled or in kit form.
Several manufacturers were selling spare parts allowing to assemble progressively and at low cost a basic system.
The first step consisted in acquiring a box with a power supply and a bus card.
One had to choose then amongst several CPU cards available: Motorola 6800, MOS 6502, Intel 8080 and 8085 or Zilog Z80. The cards were provided assembled or in kit form. One had then to solder the components on the card.
A third essential part, the RAM card. It was composed of 2 to 64 Kb of static or dynamic memory chip.
At this stage, the computer was able to operate... providing that one could communicate with it! A teletype or video terminal plugged in the computer's serial port was then necessary.
After a few days of operation, the user noticed that he would most probably need to buy a backup system to save his programs. For a few hundred $ more, he would rapidly buy a card punch or a cassette recorder with the additional interface card.
Though his computer was working correctly and that our fanatic already spent approximately $1500, he's not yet acquainted that he'll have to spend approximately twice the price in the next months to purchase more memory, communication cards, one or two floppy drives, a printer, a modem...
In 1977, when one would like to acquire a real computer, one had to be passionate, very handy... and rich!