The Tech Nut

Hello, everyone anyone who is a close follower of this blog will know that this is my second on post on The Tech Nut. (Well,now everyone else knows as well). Without further delay I’d like to give a small introduction to this post - As most of the people know Intel is one of the most famous companies of today in the field of microprocessors and has reached a height where is it rivaled by few others (AMD for example). Yet few would bother about knowing the history up of Intel’s processors. I have given the line up below and will talk about the first four processors (Source:Wikipedia).

4004 • 4040 • 8008 • 8080 • 8085 • iAPX 432 • i860 • i960 • 8086 • 8088 • 80186 • 80188 • 80286 • 80386 • 80486 • Pentium • Pentium Pro • Pentium II • Pentium III • Itanium • Pentium 4 • Pentium D • Pentium Extreme Edition • Pentium M • Pentium Dual-Core • Core • Core 2 • Celeron • Xeon • XScale • Itanium 2

 

The Intel 4004

The Intel 4004, is a 4-bit central processing unit (CPU) released by Intel Corp. in 1971, is widely considered to be the world’s first commercial single-chip microprocessor. The 4004 employed a 10μm silicon-gate PMOS(p-type metal oxide semiconductor) technology and could execute approximately 60,000 instructions per second.

The 4004 was released in 16-pin CERDIP packaging on November 15, 1971. The 4004 is the first computer processor designed and manufactured by chip maker Intel, which previously made semiconductor memory chips. The chief designers of the chip were Federico Faggin (project leader and chip designer) and Ted Hoff (architecture) of Intel and Masatoshi Shima of Busicom (later of ZiLOG). Shima designed the Busicom calculator firmware and assisted Faggin during the implementation.

Originally designed for the Japanese company Busicom to be used in their line of calculators (instead of the complex special purpose calculator chipset that Busicom had designed themselves and brought to Intel to have made, which Intel determined was too complex to make with the technology they had at the time), the 4004 was also provided with a family of custom support chips ( e.g., each “Program ROM” internally latched for its own use the 4004’s 12-bit program address, which allowed 4 KB memory access from the 4-bit address bus if all 16 ROMs were installed). The 4004 circuit was built of 2,250 transistors, and was followed the next year by the first ever 8-bit microprocessor, the 3,300 transistor 8008 (and the 4040, a revised 4004).

Now, after somewhat of an introduction to the Intel 4004 let us come to the technical specifictions.(I again say that most of this has been taken from Wikipedia and I feel it is no point bothering to read the whole article as I have copied almost the whole article.) The Intel 4004 had

• Maximum clock speed is 740 kHz
• Separate program and data storage (i.e., a Harvard architecture). Contrary to most Harvard architecture designs, however, which use separate buses, the 4004, with its need to keep pin count down, uses a single multiplexed 4-bit bus for transferring:
  • 12-bit addresses
  • 8-bit instructions
  • 4-bit data words
• Instruction set contains 46 instructions (of which 41 are 8 bits wide and 5 are 16 bits wide)
• Register set contains 16 registers of 4 bits each
• Internal subroutine stack is 3 levels deep

Microarchitecture and pinout

Intel 4004 architectural block diagram.

Intel 4004 DIP chip pinout.

 

Custom support chips

• 4001: 256-byte ROM (256 8-bit program instructions), and one built-in 4-bit I/O port
• 4002: 40-byte RAM (80 4-bit data words), and one built-in 4-bit output port; the RAM portion of the chip is organized into four “registers” of twenty 4-bit words:
  • 16 data words (used for mantissa digits in the original calculator design)
  • 4 status words (used for exponent digits and signs in the original calculator design)
• 4003: 10-bit parallel output shift register for scanning keyboards, displays, printers, etc.
• 4008: 8-bit address latch for access to standard memory chips, and one built-in 4-bit chip select and I/O port
• 4009: program and I/O access converter to standard memory and I/O chips.

The second processor which is the Intel 4040 has less to say as compared to the earlier one as it is almost if I may say an “updated” version of the Intel 4004.

The Intel 4040

 

The Intel 4040 microprocessor was the successor to the Intel 4004. It was introduced in 1974. The 4040 employed a 10μm silicon-gate PMOS technology and could execute approximately 60,000 instructions per second.

New features

• Interrupt
• Single Step

Extensions

• Instruction Set expanded to 60 instructions
• Program memory expanded to 8 KiB
• Registers expanded to 24
• Subroutine stack expanded to 7 levels deep

Designers

Federico Faggin proposed the project, formulated the architecture and led the design. The detailed design was done by Tom Innes.

New support chips

• 4201 - Clock Generator 500 to 740 kHz using 4 to 5.185 MHz crystals
• 4308 - 1 KiB ROM
• 4207 - General Purpose byte Output port
• 4209 - General Purpose byte Input port
• 4211 - General Purpose byte I/O port
• 4289 - Standard Memory Interface (replaces 4008/4009)
• 4702 - 256 byte UVEPROM
• 4316 - 2 KiB ROM
• 4101 - 256 4-bit word RAM

The third processor was the Intel 8008 which is again not as signicant as many others but still an advancement in the field of microprocessors.

The Intel 8008

The Intel 8008 was an early microprocessor designed and manufactured by Intel and introduced in April, 1972. The 8008, originally codenamed 1201, was originally commissioned by Computer Terminal Corporation for use in its Datapoint 2200 programmable terminal, but because the chip was delivered late and did not meet CTC’s performance goals, the chip was not used in the 2200. An agreement between Intel and CTC permitted Intel to market the chip to other customers.

Implemented in 10μm silicon-gate PMOS, initial versions of the 8008 ran at 0.5 MHz, later increased in the 8008-1 to 0.8 MHz. While a little slower in terms of instructions per second (45,000 to 100,000) [1] than the 4-bit Intel 4004 and Intel 4040, the fact that the 8008 processed data eight bits at a time and could access significantly more RAM actually gave it 3 to 4 times the true processing power of the 4-bit chips.

The instruction set of the 8008 and subsequent Intel CISC CPUs were heavily based on CTC’s design.

The chip (limited by its 18 pin DIP packaging) had a single 8-bit bus and required a significant amount of external support logic. For example, the 14-bit address, which could access “16 K x 8 bits of memory”^[1], needed to be latched by some of this logic into an external Memory Address Register (MAR). The 8008 could access 8 input ports and 24 output ports.

For controller and CRT terminal use this was an acceptable design, but it was too difficult to use for most other tasks. A few early computer designs were based on it, but most would use the later and greatly improved Intel 8080 instead.

The 8008 family is also referred to as the MCS-8.
The next one which is the Intel 8080 (and the last one for this post because I know half of you would have already lost interest and even the people who might have been interested would also give up soon) was a very significant model in the Intel’s line. This is one article that has been majorly edited so as not to fill up entire loads of junk.

The Intel 8080

The Intel 8080 was an early microprocessor designed and manufactured by Intel. The 8-bit CPU was released in April 1974 running at 2 MHz (at 640,000 instructions per second), and is generally considered to be the first truly usable microprocessor CPU design. It was implemented in NMOS.

Programming model

The Intel 8080 was the successor to the Intel 8008; this was due to its being assembly language source-compatible, since it used the same instruction set developed by Computer Terminal Corporation. The 8080’s large 40 pin DIP packaging permitted it to provide a 16-bit address bus and an 8-bit data bus, allowing easy access to 64 kilobytes of memory.

Registers

The processor had seven 8-bit registers, six of which could be combined into three 16-bit register pairs (BC, DE and HL). It also had the 8-bit accumulator, the 16-bit stack pointer to memory (replacing the 8008’s internal stack), and a 16-bit program counter.

16-bit operations

Despite the fact that the 8080 was generally an 8-bit processor, it was also able to load immediate any register pair (LXI), increment or decrement any register pair (INX, DCX), add the register pairs (DAD), switch HL with DE (XCHG) and perform the 16-bit arithmetical shift (DAD H) with one command. Hence some 16-bit operations were already possible.

Input output port space

The 8080 supported up to 256 input/output (I/O) ports, accessed from programs via dedicated I/O instructions—each instruction taking an I/O port address as its operand. This scheme—using a separate I/O address space—is now less commonly used than memory mapping of I/O ports/devices. At the time of the 8080’s launch, this I/O mapping scheme was seen as an advantage, as it freed up the processor’s limited number of address pins for the memory address space. In most other CPU architectures, however, the mapping of I/O ports in a common address space both for memory and I/O, gave a simpler instruction set; no need for separate I/O instructions. The 8080-style I/O port scheme continued into the Intel 8085 and x86 families of microprocessors, as well as the Zilog Z80 series.

Pin usage

The address bus had its own 16 pins, and the data bus had 8 pins that were possible to use without any multiplexing. Using the two additional pins (read and write signals), it was possible to assemble simple microprocessor devices very easily. Only the separate IO space, interrupts and DMA required additional chips to decode the processor pin signals. However the processor load capacity was limited, and even simple computers frequently contained bus amplifiers.

There was a huge table after this which I refrained from adding owing to the length of the post.

Applications and successors

The 8080 was used in many early microcomputers, such as the MITS Altair 8800 Computer, Processor Technology SOL-20 Terminal Computer and IMSAI 8080 Microcomputer, forming the basis for machines running the CP/M operating system (the later, fully compatible and more capable, Zilog Z80 processor would capitalize on this, with Z80 & CP/M becoming the dominant CPU & OS combination of the period much like x86 & MS-DOS for the PC a decade later). The first single-board microcomputer was based on the 8080. The company Landis & Gyr used it on its electrical metering data acquisition equipment, the Datagyr FAB during the early eighties.

In addition, several early arcade video games were built around the 8080 microprocessor. Space Invaders was perhaps the most popular such title.

Shortly after the launch of the 8080, the Motorola 6800 competing design was introduced, and after that, the MOS Technology 6502Zilog introduced the Z80, which had a compatible machine-language instruction set and initially used the same assembly language as the 8080, but for legal reasons, Zilog developed a syntactically-different alternative assembly language for the Z80. At Intel, the 8080 was followed by the compatible and electrically more elegant 8085, and later by the assembly language compatible 16-bit 8086 and then the 8/16-bit 8088, which was selected by IBM for its new PC to be launched in 1981. The 8080, via its ISA, thus made a lasting impact on computer history. variation of the 6800.

The Soviet Union manufactured a complete 8080 analog named KP580ИK80 (later marked as KP580BM80), where even the pins were placed identically. This processor was the base of the Radio86RK probably the most popular amateur single-board computer in the Soviet Union. Radio86RK’s predecessor was the Micro-80 ( Микро-80 in Russian), and its successor the Orion-128 (Орион-128 in Russian) which had a graphical display.

The 8080 also changed how computers were created. When the 8080 was introduced, computer systems were usually created by computer manufacturers such as Digital Equipment Corporation, Hewlett Packard, or IBM. A manufacturer would produce the entire computer, including processor, terminals, and system software such as compilers and operating system. The 8080 was actually designed for just about any application except a complete computer system. Hewlett Packard developed the HP 2640 series of smart terminals around the 8080. The HP 2647 was a terminal which ran BASIC on the 8080. Microsoft would create the first popular programming language for the 8080, and would later acquire DOS for the IBM-PC.

That is the end of this post and next time I will make sure that I don’t write anything about the insignificant processors and only the important ones.