On Microprocessors

by John Carlsen – February 29, 2024

A microprocessor is a type of integrated circuit, which is semiconductor device that integrates many components of a larger electronic circuit into a single device. The integrated components generally include transistors, resistors, and capacitors.

Integrated Circuits and Silicon Chips

Each integrated circuit is usually a single rectangular chip fabricated on a flat round wafer, which is sliced from an ingot of sputtered silicon atoms.

They are fabricated through processes that combine chemical doping (vapor deposition), printing (as through electron-beam lithography from reticles for each process layer), and growing non-conductive oxides.

When wafer fabrication is complete, the wafer is scored in two directions along the boundaries of each rectangular die.

While still on the wafer, each die is tested; the bad ones are marked for exclusion and the good ones are removed as “chips” from the wafer and usually packaged inside plastic or ceramic along with a leadframe so that it may be mounted more easily on a printed circuit board (PCB), either soldered directly or inserted into a soldered socket. Some applications (such as early digital wristwatches) use a process known as chip on board (COB) to mount chips directly to printed circuit boards, where they are wire bonded and encapsulated in protective plastic.

Though germanium or other semiconducting elements may be used, many chips were made from silicon and are therefore called silicon chips. Many early silicon chips were made in California’s Santa Clara Valley, leading to its now-popular metonym Silicon Valley.

The Blocks from which a Computer is Built

The first commercially-available transistorized computers (second-generation computers) became available in the late 1950s. Many computer companies then built transistor-based interchangeable modules to perform basic logic functions on printed circuit board assemblies.

My father worked for one of these companies, Control Data Corporation, and I started learning about electronics and computers with some of the transistor-based assemblies it discarded.

The first computer based on silicon integrated circuits was the Apollo Guidance Computer (AGC), which was introduced in 1966 and enabled people to visit the Moon beginning in 1969.

Small-Scale Integration

The logic chips in the Apollo Guidance Computer are an example of small-scale integration (SSI), through which small numbers of multiple transistors on single chips integrate a function of a larger of a circuit.

The designers of the Apollo Guidance Computer’s original architecture (Block I) were able to simplify their task of qualifying components for spaceflight by building it using only one type of device, which contained two isolated (dual) triple-input NOR gates. This was possible because NOR gates (and NAND gates) are universal logic gates from which any other gate can be made. (Some other types of integrated circuits were added to the later Block II design.)

(These NOR devices were fabricated by Fairchild Semiconductor, at what I believe was either of its Silicon Valley facilities—in north Mountain View or on Bernal Road in south San Jose—which were both later among many Environmental Protection Agency toxic waste Superfund sites in Silicon Valley directly attributable to the early semiconductor industry that gave it its name.)

(In 2019, as part of a celebration of the 50th anniversary of the first people landing on the Moon, for some friends I designed a printed circuit board that connected to and helped some friends restore an Apollo Guidance Computer to operation. Shortly afterward, I happened to meet Margaret Hamilton, who directed software engineering for the Apollo Program and for her work received the Presidential Medal of Freedom from Barack Obama in 2016.)

Types of Transistor Logic

These devices used a resistor-transistor logic (RTL) configuration, through which resistors are used to bias nodes of a circuit toward a binary logic state’s voltage level when not actively driven by a transistor toward the voltage level representing the other binary state.

Texas Instruments (TI) had introduced a series of SSI integrated circuits with transistor-transistor logic (TTL) by 1973, when it released its (uniquely hardcover) TTL Data Book for Design Engineers.

As I entered my teenage years, my friend (and formerly my father’s office mate while at the Sunnyvale office of Control Data Corporation) LaFarr Stuart “loaned” me a copy of this book (which I still have and treasure) along with a logic trainer kit made by Digital Equipment Corporation (DEC) and likely intended for college students. My junior high school had once been a high school, so I was able to borrow from its library a copy of Don Lancaster’s 1974 The TTL Cookbook.

One key benefit of TTL is that it doesn’t need as much power to operate as RTL (and DTL, which is diode-transistor logic). This is because the addition of a second transistor effectively shuts off power to the output when the other transistor drives it.

The term TTL describes the configuration of the devices to create the logic circuit, not their construction. Although the first TTL devices used bipolar junction transistors (BJTs), TTL also includes later devices made using field-effect transistors (FETs) including those made using metal-oxide-silicon (MOS) processes, sometimes called MOSFETs.

A key benefit of MOSFETs is that they switch based on voltage levels, not varying flows of current as in BJTs. So, MOSFET circuits are more power efficient than similar circuits constructed from BJTs.

Using MOSFETs, a TTL configuration requires types of both negative-channel MOS (NMOS) and positive-channel MOS (PMOS), a combination called complimentary metal-oxide-silicon (CMOS).

Note that the 6502, 6502A, 6502B, and 6502C were NMOS devices. (The 6502 was released in 1975 and 6502B was used in early Atari 8-bit computers starting in 1979.) The WDC 65C02 was a CMOS device released in 1983.

A Survey of Microprocessors

The first commercially-available microprocessors emerged in 1971 using transistors with gates that had lengths of 10 microns (micrometers, or millionths of a meter). By 2017, some microprocessors used transistors with gate lengths 1000 times smaller.

Year	Company	Device	Process Node	Maximum Clock Speed	Package (Contacts)	Data Bus Width	Address Bus Width	RAM Limit (key)	Notable Uses
1971	Intel	4004	10 µm PMOS (+15 V)	740-750 kHz	DIP (16)	4 bits	12 bits	2 kiB	Nippon Calculating Machine Corporation Busicom 141-PF printing calculator
1971	TI	TMS1802NC (TMS0100 family)	? µm	? kHz	?	? bits	? bits	? kiB	TI Datamath calculator
1972	Rockwell	PPS-4 (10660)	? µm metal gate (−17 V)	256 kHz	QIP (42)	8 bits (4 bits data)	12 bits	4 kiB
1972	Intel	8008	10 µm PMOS	500-800 kHz	DIP (18)	8 bits	14 bits	16 kiB
1974	TI	TMS1000	? µm PMOS (−9 V or −15 V), NMOS & CMOS (5 V)	~300 kHz	DIP (28, 40)	? bits	? bits	? kiB	Speak & Spell toy Big Trak toy Simon game
1974	RCA	1802 (CDP1801R and CDP1801U)	? µm CMOS (4 V to 10.5 V	3.2-6.4 MHz	DIP (24)	? bits	? bits	? kiB
1974	Intel	4040	10 µm	500-740 kHz	DIP (24)	? bits	? bits	? kiB
1974	Intel	8080	6 µm	2 MHz	DIP (40)	8 bits	16 bits	64 kiB	1975 Altair 8800 (2 MHz)
1974	Motorola	6800	6 µm	1-2 MHz	DIP (40)	8 bits	16 bits	64 kiB
1975	GI	CP1600	? µm NMOS (−3, +5, +12 V)	? kHz	?	? bits	? bits	? kiB	Mattel Intellivision video game console
1975	Rockwell	PPS-4/2 (11660)	? µm metal gate (−17 V)	256 kHz	?	8 bits	12 bits	4 kiB
1975	MOS Technology	6501	8 µm		DIP (40)	8 bits	16 bits	64 kiB
1975	MOS Technology	6502	8 µm	1-3 MHz	DIP (40)	8 bits	16 bits	64 kiB	1977 Apple II 1979 Atari Lunar Lander arcade game 1979 Atari Asteroids arcade game
1975	MOS Technology	6507	8 µm		DIP (28)	8 bits	13 bits	8 kiB	1977 Atari VCS (2600) (1.19 MHz)
1976	Rockwell	PPS-4/1	? µm PMOS	40-100 kHz	?	8 bits	12 bits	4 kiB
1976	Intel	8085	3 µm	3, 5, 6 MHz	DIP (40)	8 bits	16 bits	64 kiB
1976	Zilog	Z80	4 µm	2.5 MHz	DIP (40) PLCC (44) QFP (44)	8 bits	16 bits	64 kiB
≤1979	MOS Technology	6502A		1.5-2 MHz	DIP (40)	8 bits	16 bits	64 kiB	1981 Atari Asteroids Deluxe arcade game 1981 (Acorn) BBC Micro
1978	Intel	8086	3 µm		DIP (40)	16 bits	20 bits	2 MiB
≤1979	MOS Technology	6502B		3 MHz	DIP (40)	8 bits	16 bits	64 kiB	1979 Atari 8-bit computers (1.77/1.79 MHz, PAL/NTSC)
1979	Intel	8088	3 µm	5-16 MHz	DIP (40) PLCC (44)	8 bits	20 bits	2 MiB	1982 IBM 5150 PC (4.77 MHz) 1983 IBM 5160 PC/XT (4.77 MHz)
1979	Motorola	68000	3 µm	4 MHz	DIP (68) CLCC (68) PLCC (68)	16/32 bits	24 bits	16 MiB	1982 Atari Food Fight arcade game 1984 Apple Macintosh 1985 Commodore Amiga 1985 Atari ST 1988 Sega Genesis 1993 Atari Jaguar
≤1980	Zilog	Z80A		4 MHz	DIP (40) PLCC (44) QFP (44)	8 bits	16 bits	64 kiB	1980 Pac-Man arcade game
1982	Motorola	68010		8-16.67 MHz	DIP (68) PGA	16/32 bits	24 bits	16 MiB
	Motorola	68012			PGA (84)	16/32 bits	24 bits	16 MiB
1982	Intel	80186	3 µm to 1 µm		PLCC (68) LCC (68) PGA (68)	16 bits	20 bits	2 MiB
1982	Intel	80286	1.5 µm	4 MHz	PLCC (68) LCC (68) PGA (68) LLCC	16 bits	24 bits	16 MiB	1984 IBM 5170 PC/AT
1982	Zilog	Z80H		8 MHz	DIP (40) PLCC (44) QFP (44)	8 bits	16 bits	64 kiB
1983	WDC	65C02		1-14 MHz	DIP (40) PLCC QFP	8 bits	16 bits	64 kiB	Apple //c, Atari Lynx, NEC PC Engine
≤1983	Zilog	Z80B		6 MHz	DIP (40) PLCC (44) QFP (64)	8 bits	16 bits	64 kiB
1984	Motorola	68020		12.5-33 MHz	PGA (169)	32 bits	32 bits	4 GiB
1985	WDC	65C816		1-14 MHz	DIP (40) PLCC (44)	8 bits	24 bits	16 MiB	SNES
1985	Intel	80286-10 80286-12	1.5 µm	10, 12 MHz	PLCC (68) LCC (68) PGA (68)	16 bits	24 bits	16 MiB
1985	Intel	80386 (i386)	1.5-1 µm	10, 12 MHz	PGA (132) PQFP (132) PGA (68)	32 bits	32 bits	4 Gib
≤1986	Intel	8080A		2.083 MHz	DIP (40)	8 bits	16 bits	64 kiB
≤1986	Intel	8080A-1 (8080B)		3.125 MHz	DIP (40)	8 bits	16 bits	64 kiB
≤1986	Intel	8080A-2		2.63 MHz	DIP (40)	8 bits	16 bits	64 kiB
1986	MIPS	R2000		8.3 MHz 12.5 MHz 15 MHz	?	32 bits	? bits	? kiB
1987	Motorola	68030		16-50 MHz	QFP (132) PGA (169)	32 bits	32 bits	4 GiB
1988	AMD	Am29000				32 bits
1988	MIPS	R2000A		12.5 MHz 16.67 MHz	?	32 bits	? bits	? kiB
1988	MIPS	R3000		20 MHz 25 MHz 33.33 MHz	?	32 bits	? bits	? kiB
1989	Intel	80486 (i486)	1-0.6 µm	16-100 MHz	PQFP (196) SQFP (208)	32 bits	32 bits	4 GiB
1989	MIPS	R3000A		40 MHz	?	32 bits	? bits	? kiB	Sony PlayStation
1990	Motorola	68040		25-40 MHz	CPGA (179) QFP (184)	32 bits	32 bits	4 GiB
1991	AMD	Am29050	1 µm	20 MHz 25 MHz 33 MHz 40 MHz		32 bits
1993	Intel	80501 Pentium (i586) P5	0.8 µm	60 MHz	PGA (273) (Socket 4)	32 bits
1994	AMD	Am29040	0.7 µm	33 MHz 40 MHz 50 MHz		32 bits
1994	Motorola	68060		50-75 MHz		32 bits	32 bits	4 GiB
1994	Intel	80502 Pentium (i586) P54C	0.6 µm	75 MHz, 90 MHz, 100 MHz	SPGA (320) (Socket 5)	32 bits
1995	Intel	80502 Pentium (i586) P54CQS	0.35 µm	120 MHz	Socket 5?	32 bits
1995?	Intel	80502 Pentium (i586) P54CS	0.35 µm	133 MHz, 150 MHz, 166 MHz, 200 MHz	Socket 7	32 bits
1995	Intel	80521 Pentium Pro (i686)	0.6 µm 0.5 µm 0.35µm	150 MHz, 166 MHz, 180 MHz, 200 MHz	Socket 7	32 bits	36 bits	64 GiB
1996	AMD	K5	0.5 µm	75-133 MHz	Socket 5 Socket 7	32 bits
1997	Intel	80503 Pentium MMX (i586) P55C	0.28 µm	120 MHz (mobile), 133 MHz (mobile), 150 MHz (mobile), 166 MHz, 200 MHz, 233 MHz	MCM (387) (Socket 8)	32 bits
2003	AMD	Athlon 64 FX (K8)	0.13 µm	2200 MHz 2400 MHz		64 bits			Newisys 2100
2006	AMD	Athlon 64 FX (K8)	0.09 µm (90 nm)	3200 MHz		64 bits
2006	Intel	Core	65-45 nm	933 Mhz-3.5 GHz		64 bits
2017	Intel	Core 2 Duo	10 nm			64 bits	52 bits	4 PiB	practical limit
2017	Intel	Core 2 Duo	10 nm			64 bits	64 bits	16 EiB	theoretical limit