Lesson 1: Intoduction to the Mark-8
From the original article in Radio-Electronics
by Jonathan A. Titus
The heart of the Mark-8 Minicomputer is an Intel 8008 microprocessor IC that contains
all of the arithmetic registers, subroutine registers and most of the control
logic necessary to interface the microprocessor with semiconductor memories as
well as input and output registers. Standard TTL type IC's are used throughout and
commonly available 1101. 1101A and 1101A1 type memories are used for the central
storage. The microprocessor with its associated logic will be refered to as the central
processor unit. or CPU.
The central processor unit is an 8-bit parallel processor. A string of eight binary
bits. D7 through D0 is used to indicate the
instruction data or memory locations. Rather than repeat, "eight bits of binary
data " , we refer to the eight bits as a byte. As you will note, some of the instructions
take up to three bytes of data and they are, therefore, called three-byte instructions.
The computer takes 20ms to execute each byte of these instructions, so the time to
execute any of the basic instructions may vary from 20 to 60 ms. The time that the
computer takes to execute one byte of the instruction is called the computer's cycle
time. Most minicomputers have a cycle time that is about ten times faster than the
Mark-8, but this will not restrict the use of this Minicomputer in most situations.
The Intel 8008 microprocessor provides us with some sophisticated features, only
found on larger, more costly computers. These include a pointer register, interrupt
pointers and a stack register for multiple subroutines.
Read More: Mark-8 Construction.pdf [2.54 MB]
Read More: Mark-8 Schematics.pdf [7.88 MB]
Read More: Mark-8 Circuit Boards.pdf [31.2 MB]