Section One: Before the Great Dark Cloud.
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Part I: The Intel 4004 (1972)
The first single chip CPU was the Intel 4004, a 4-bit processor meant for
a calculator. It processed data in 4 bits, but its instructions were 8 bits long. Internally, it featured four 12 bit(?) registers which acted as an internal evaluation stack. The Stack Pointer pointed to one of these registers, not a memory location (only CALL and RET instructions operated on the Stack Pointer). There were also sixteen 4-bit (or eight 8-bit) general purpose registers
The 4004 had 46 instructions. Intel created an 8-bit version of this, the
8008 (intended for a terminal controller). [for additional information, see Appendix B]
Part II: The Intel 4040 and 8080
The 4040 was compatible with the 4004 instruction set - the 4040 had 60
instructions, which included the 46 4004 instructions. The 8080 was similar to the 4040, except being 8 bits wide.
The 8080 had a 16 bit address bus, and an 8 bit data bus. Internally it
had seven 8 bit registers (six which could also be combined as three 16 bit registers), a 16 bit stack pointer (the stack was stored in memory, not in an internal register set), and 16 bit program counter. It also had several I/O ports - 256 of them, so I/O devices could be hooked up without taking away or interfering with the addressing space.
Appearing in IEEE Computer 1972:
NEW PRODUCTS
FEATURE PRODUCT
COMPUTER ON A CHIP
Intel has introduced an integrated CPU complete with
a 4-bit parallel adder, sixteen 4-bit registers, an accumula- tor and a push-down stack on one chip. It's one of a family of four new ICs which comprise the MCS-4 micro computer system–the first system to bring the power and flexibility of a dedicated general-purpose computer at low cost in as few as two dual in-line packages.
MSC-4 systems provide complete computing and con-
trol functions for test systems, data terminals, billing machines, measuring systems, numeric control systems and process control systems.
The heart of any MSC-4 system is a Type 4004 CPU,
which incudes a set of 45 instructions. Adding one or more Type 4001 ROMs for program storage and data tables gives a fully functioning micro-programmed com- puter. Add Type 4002 RAMs for read-write memory and Type 4003 registers to expand the output ports.
Using no curcuitry other than ICs from this family of
four, a system with 4096 8-bit bytes of ROM storage and 5120 bits of RAM storage can be created. For rapid turn-around or only a few systems, Intel's erasable and re-programmable ROM, Type 1701, may be substituted for the Type 4001 mask-programmed ROM.
MCS-4 systems interface easily with switches, key-
boards, displays, teletypewriters, printers, readers, A-D converters and other popular peripherals. For further information, circle the reader service card 87 or call Intel at (408) 246-7501.
Circle 87 on Reader Service Card
COMPUTER/JANUARY/FEBRUARY 1971/71