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I bought my
first computer, a Mark-8, second hand in 1976. It was built
by
Mr. Wright, a friend of our family. Mr. Wright was kind
enough to
include an oscilloscope, in the purchase, to aid in any
repairs.
This was my start into digital electronics! The computer included two peripherals, a baudot KSR TTY (keyboard input & printing), plus a calculator keypad. Pictured above to the left of the computer is the interface box for both of these (also built by Mr. Wright). After a while I was bothered by the fact that some RAM had problem bits. Being the first digital circuit I'd ever attempted to repair, I jumped in without knowing what I was doing. To say the least I caused more harm than good. The failed repair attempt made the Mark-8 unusable. This prompted me to start reading up on digital circuit design. After some time (now 1978) I designed a replacement 4K card using the common 2102 1Kx1 static RAM chip. The Mark-8 worked again! At some time later; one of the chips in the first 1K went bad, and this is why one sees a missing chip from the top (fourth K) row. To the left are the "LED Register Display Board", the "Output Latch Board", and the "Address Latch Board" (top to bottom respectively). To the right are the "Data Input MPX Board", the "CPU Board", and "Craig's 4K Board". The original 1K "Memory Board" is pictured below-left. Around 1980 I retired the Mark-8 when I built my second computer, an S-100 Z-80 system using Jade Big-Z, and Jade DD. The last time I had the Mark-8 powered up and running was back in 1998. Click on pictures for more images. |
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