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All Obzoryzhelezovse reviews of computer hardware
Topics: processor
The evolution of processors.
Part 1: The 8 bit Era
13.06.2014
Oleg Kolenchenko, info@ferra.ru
Print version
We continue the series of articles devoted to the history of the development of the main components of personal computers, and we invite you to remember and follow how central processing units evolved.
The first part of this series of materials will focus on the development of integrated solutions in the 70s of the last century.
Table of contents
1940s 1960s Intel 4004 Intel 8008 Intel 8080 Zilog Z80 ZX Spectrum Motorola 6800 Processor MOS Technology 6502 Instead of conclusion
Most recently, we told you about the history of the development of video cards (part 1, part 2, part 3 and part 4), starting from the first MDA and CGA graphics adapters and ending with the latest AMD and NVIDIA architectures.
Now it is the turn to follow the development of central processing units — an equally important component of any computer.
In this part of the material, we will talk about the 1970s, and therefore the first 4 and 8 bit solutions.
The first CPUs were centipedes
1940s 1960s
Before delving into the history of the development of central processors, it is necessary to say a few words about the development of computers in general.
The first CPUs appeared in the 40s of the XX century.
Then they worked with the help of electromechanical relays and vacuum tubes, and the ferrite cores used in them served as storage devices.
For the functioning of a computer based on such chips, a huge number of processors were required.
Such a computer was a huge case the size of a fairly large room.
At the same time, it released a large amount of energy, and its speed left much to be desired.
A computer using electromechanical relays
Image source
However, already in the 1950s, transistors began to be used in the design of processors.
Thanks to their use, engineers managed to achieve a higher speed of operation of the chips, as well as reduce their power consumption, but increase reliability.
In the 1960s, the technology of manufacturing integrated circuits was developed, which made it possible to create microchips with transistors located on them.
The processor itself consisted of several such circuits.
Over time, technologies have made it possible to place an increasing number of transistors on a chip, and therefore the number of integrated circuits used in the CPU has been reduced.
Nevertheless, the processor architecture was still very, very far from what we see today.
But the release of the IBM System/360 in 1964 brought the design of the then computers and CPUs a little closer to the modern one primarily in terms of working with software.
The fact is that before the advent of this computer, all systems and processors worked only with the program code that was written specifically for them.
For the first time, IBM used a different philosophy in its computers: the entire line of CPUs with different performance supported the same set of instructions, which allowed writing software that would run under any System/360 modification.
IBM System/360 computer
Image source
By its architecture, the IBM System/360 processor was a CISC solution.
As you know, all integrated circuits are divided into two large categories: RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer).
The latter work with complex instructions, while the former work with simplified ones.
From the point of view of modern achievements, the complexity of instructions for CISC processors is that their length is not limited.
In addition, they can contain several arithmetic operations at once However, at that time, the RISC design did not exist in principle, and IBM, as well as other manufacturers, used the CISC architecture until the 1980s.
The System / 360 had some other features as well.
For example, an 8 bit byte was implemented in a computer for the first time — before that, the byte volume was 6 bits.
Also, System / 360 became the first 32 bit system in history.
The computer was also able to work with virtual memory, and the older models of the line supported the technology of virtual machines.
In short, the System/360 processor already resembled modern solutions in many ways.
Despite the high cost, the System / 360 has become relatively successful in the market.
During the presentation of the computer, about 100 thousand businessmen were present in all cities of the United States, according to an official IBM press release dated April 7, 1964.
In the first month, the American company received more than 1,000 orders for the IBM System/360 and another thousand in the next four months.
For that time, the figures are more than impressive.
The System / 360 computers were also actively used by NASA to control space flights during the Apollo program.
outbooks and other devices.
And one of the first companies that was just founded at that time was Intel, which launched the 4004 model — the world's first commercially available single chip processor.
Before proceeding directly to the 4004 processor, it is worth saying a few words about Intel itself.
It was created in 1968 by engineers Robert Noyce and Gordon Moore, who until then had worked for the benefit of Fairchild Semiconductor, and Andrew Grove.
By the way, it was Gordon Moore who published the well known "Moore's law", according to which the number of transistors in the processor doubles every year.
Already in 1969, just a year after its foundation, Intel received an order from the Japanese company Nippon Calculating Machine (Busicon Corp.) for the production of 12 chips for high performance desktop calculators.
The initial design of the chips was proposed by Nippon itself.
However, this architecture did not appeal to Intel engineers, and an employee of the American company Ted Hoff proposed to reduce the number of chips to four by using a universal central processor that would be responsible for arithmetic and logical functions.
In addition to the CPU, the architecture of the chips included RAM for storing user data, as well as ROM for storing software.
After the approval of the final structure of the chips, work continued on the design of the microprocessor.
In April 1970, the Italian physicist Federico Fagin, who had also worked at Fairchild, joined the Intel engineering team.
He had extensive experience in the field of logical design of computers and MOS (metal oxide semiconductor) technologies with silicon gates.
It was thanks to Federico's contribution that Intel engineers managed to combine all the chips into one chip.
So the world's first microprocessor 4004 was born.
Intel 4004 processor
Image source
As for the technical characteristics of the Intel 4004, then, by today's standards, of course, they were more than modest.
The chip was produced according to a 10 micron process technology, contained 2300 transistors and operated at a frequency of 740 kHz, which meant that it was possible to perform 92,600 operations per second.
DIP16 packaging was used as a form factor.
The dimensions of the Intel 4004 were 3x4 mm, and there were rows of contacts on the sides.
Initially, all the rights to the chip belonged to Busicom, which intended to use the microprocessor exclusively in calculators of its own production.
However, in the end, they allowed Intel to sell its chips.
In 1971, anyone could buy a 4004 processor at a price of about $ 200.
By the way, a little later Intel bought all the rights to the processor from Busicom, predicting the important role of the chip in the subsequent miniaturization of integrated circuits.
Despite the availability of the processor, its scope of application was limited to the Busicom 141 PF calculator.
There have also been rumors for a long time that Intel 4004 was used in the design of the onboard computer of the unmanned Pioneer 10 spacecraft, which became the first interplanetary probe to fly near Jupiter.
These rumors are directly refuted by the fact that the Pioneer's onboard computers had 18 or 16 bit bitness, while the Intel 4004 was a 4 bit processor.
However, it is worth noting that NASA engineers considered the possibility of using it in their devices, but considered the chip insufficiently tested for such purposes.
Intel 4040 processor
Image source
Three years after the release of the Intel 4004 processor, its successor, the 4 — bit Intel 4040, was released.
The chip was produced according to the same 10 microns process technology and worked at the same clock frequency of 740 kHz.
However, the processor has become a little "more complex" and has received a richer set of functions.
So, the 4040 contained 3000 transistors (700 more than the 4004).
The form factor of the processor remained the same, but instead of a 16 pin one, a 24 pin DIP was used.
Among the improvements of the 4040, it is worth noting support for 14 new commands, increased stack depth to 7 levels, as well as support for interrupts.
The "Fortieth" was used mainly in test devices and equipment management.
Intel 8008
In addition to 4 bit processors, in the early 70s, an 8 — bit model 8008 appeared in Intel's arsenal.
At its core, the chip was an 8 bit version of the 4004 processor with a lower clock frequency.
This should not be surprising, because the development of the 8008 model was carried out in parallel with the development of the 4004.
So, in 1969, the Computer Terminal Corporation (later Datapoint) commissioned Intel to create a processor for Datapoint terminals, providing them with an architecture diagram.
As in the case of the 4004 model, Ted Hoff proposed to integrate all the chips into one chip, and CTC agreed with this proposal.
The development was gradually coming to its end, but in 1970 CTC abandoned both the chip and further cooperation with Intel.
The reasons were banal: Intel engineers did not invest in the established development deadlines, and the functionality of the provided "stone" did not meet the requirements of CTC.
The contract between the two companies was broken, the rights to all the developments remained with Intel.
The Japanese company Seiko became interested in the new chip, whose engineers wanted to use the new processor in their calculators.
Intel 8008 processor
Image source
One way or another, but after the termination of cooperation with CTC, Intel renamed the chip under development to 8008.
In April 1972, this processor became available for order at a price of $ 120.
After Intel was left without CTC support, the company's camp was cautious about the commercial prospects of the new chip, but doubts were in vain — the processor sold well.
The technical characteristics of the 8008 were in many ways similar to the 4004.
The processor was produced in an 18 pin DIP form factor according to 10 microns technological standards and contained 3500 transistors.
The internal stack supported 8 levels, and the amount of supported external memory was up to 16 Kbytes.
The clock frequency of the 8008 was set at 500 kHz (240 kHz lower than that of the 4004).
Due to this, the 8 bit Intel processor often lost in speed to the 4 bit one.
Several computer systems were built on the basis of the 8008.
The first of them was a not very well known project called The Sac State 8008.
This system was developed at the University of Sacramento under the supervision of engineer Bill Pentz.
Despite the fact that for a long time the Altair 8800 system was considered the first microcomputer created, it is The Sac State 8008 that is such.
The project was completed in 1972 and represented a fully functional computer for processing and storing medical records of patients.
The computer included an 8008 processor, a hard disk, 8 KB of RAM, a color display, an interface for connecting to mainframes, as well as its own operating system.
The cost of such a system was extremely high, so The Sac State 8008 was never able to get proper distribution, although it had no competitors in terms of performance for quite a long time.
This is what The Sac State 8008 looked like
Image source
However, The Sac State 8008 is not the only computer built on the basis of the 8008 processor.
Other systems were also created, such as the American SCELBI 8H, the French Micral N and the Canadian MCM/70.
Intel 8080
As in the case of the 4004 processor, after a while the 8008 also received an update in the face of the 8080 chip.
However, in the case of an 8 bit solution, the changes made to the processor architecture were much more significant.
The Intel 8080 was introduced in April 1974.
First of all, it should be noted that the production of the processor was transferred to a new 6 microns process technology.
Moreover, the production used the technology of N MOSFETs (n channel transistors) - in contrast to the 8008, which was produced using P MOSFET logic.
The use of a new technological process made it possible to place 6000 transistors on the chip.
A DIP with 40 contacts was used as a form factor.
The 8080 model received a richer set of commands, which included 16 data transfer commands, 31 commands for processing them, 28 commands for switching with direct addressing, as well as 5 control commands.
The processor's clock frequency was 2 MHz — 4 times more than that of its predecessor.
The 8080 also had a 16 bit address bus, which allowed addressing 64 KB of memory.
These innovations ensured the high performance of the new chip, which was about 10 times higher than that of the 8008.
Intel 8080 processor
Image source
The 8080 processor in its first revision contained a serious error that could lead to a hang.
The error was fixed in an updated revision of the chip, called 8080A and released only six months later.
Due to the high performance, the 8080 processor has become very popular.
It was used even in control systems for street lighting and traffic lights.
However, it was mainly used in computer systems, the most famous of which was the development of the company MITS Altair 8800, presented in 1975.
The Altair 8800 was based on the Altair BASIC operating system, and the S 100 interface was used as the bus, which a few years later became the standard for all personal computers.
The technical characteristics of the computer were more than modest.
It had only 256 bytes of RAM oh, memory, he had no keyboard and monitor.
The user worked with the computer by entering programs and data in binary form, clicking a set of small keys that could occupy two positions: upper and lower.
The result was also read in binary form by the extinguished and glowing light bulbs.
Nevertheless, the Altair 8800 became so popular that such a small company as MITS simply did not have time to meet the demand for computers.
The popularity of the computer was directly promoted by its low cost — 621 US dollars.
At the same time, for 439 US dollars, it was possible to purchase a computer in disassembled form.
Altair 8800 computer
Image source
Returning to the topic of the 8080, it should be noted that there were many clones of it on the market.
The marketing situation at that time was radically different from what we are seeing today, and it was advantageous for Intel to grant licenses to third party companies to produce copies of the 8080.
Many large companies, such as National Semiconductor, NEC, Siemens and AMD, were engaged in the production of clones.
Yes, in the 70s, AMD did not yet have its own processors — the company was engaged exclusively in the production of" remakes " of other crystals at its own capacities.
Interestingly, there was also a domestic copy of the 8080 processor.
It was developed by the Kiev Research Institute of Micro Devices and was called KR580VM80A.
Several variants of this processor were released, including for use in military facilities.
"Nezalezhny" KR580VM80A
In 1976, an updated version of the 8080 chip appeared, which received the index 8085.
The new crystal was manufactured according to a 3 micron technological process, which made it possible to place 6500 transistors on the chip.
The maximum clock frequency of the processor was 6 MHz.
The set of supported instructions contained 79 commands, among which were two new commands for managing interrupts.
Zilog Z80
The main event after the release of 8080 was the dismissal of Federico Fagin.
The Italian did not agree with the internal policy of the company and decided to leave.
Together with former Intel manager Ralph Ungermann and Japanese engineer Masatoshi Shima, he founded the company Zilog.
Immediately after that, the development of a new processor similar in architecture to the 8080 began.
So, in July 1976, the Zilog Z80 processor appeared, binary compatible with the 8080.
Federico Fagin (left)
Image source
Compared to the Intel 8080, the Zilog Z80 had many improvements, for example, an expanded instruction set, new registers and instructions for them, new interrupt modes, two separate register blocks, as well as a built in dynamic memory regeneration scheme.
In addition, the cost of the Z80 was much lower than the 8080.
As for the technical characteristics, the processor was produced according to 3 microns technological standards using the technologies N MOSFET and CMOS.
The Z80 contained 8,500 transistors, and its area was 22.54 mm2.
The clock frequency of the Z80 ranged from 2.5 to 8 MHz.
The bit depth of the data bus was 8 bits.
The processor had a 16 bit address bus, and the amount of addressable memory was 64 Kbytes.
The Z80 was produced in several form factors: DIP40 or 44 pin PLCC and PQFP.
Zilog Z80 processor
Image source
The Z80 quickly surpassed all competing solutions in popularity, including the 8080.
The processor was used in computers of such companies as Sharp, NEC and others.
Also, the Z80 was "registered" in Sega and Nintendo consoles.
In addition, the processor was used in slot machines, modems, printers, industrial robots and many other devices.
ZX Spectrum
A special mention is worthy of a device called the ZX Spectrum, despite the fact that our current story does not concern the solutions of the 80s of the last century.
The computer was developed by the British company Sinclair Research and was released in 1982.
The ZX Spectrum was far from the first SR development.
In the early 1970s, the head of the company and its chief engineer, Clive Sinclair, were engaged in selling radio components by mail.
Closer to the mid 70s, Clive created a pocket calculator, which became the first successful invention of the company.
Note that the company did not directly develop the calculator.
They managed to find a successful combination of design, functionality and cost, thanks to which the device sold well.
The next Sinclair device also became a calculator, but with a richer set of functions.
The device was intended for a more "advanced" audience, but it failed to gain much success.
Clive Sinclair — the "father" of the ZX Spectrum
Image source
After calculators, Sinclair decided to focus on developing full fledged computers, and between 1980 and 1981, home computers of the ZX line appeared: the ZX80 and ZX81.
But the most popular solution was a system released in 1982 called the ZX Spectrum.
Initially, it was supposed to enter the market under the name ZX83, but at the last moment it was decided to rename the device to emphasize the computer's support for color images.
The ZX Spectrum has become popular, primarily due to its simplicity and cheapness.
The computer looked like a game console.
A TV, which was used as a monitor, and a cassette recorder, which performs the function of a storage device, were connected to it through external interfaces.
A multifunctional keyboard with 40 rubber keys was located on the Spectrum case.
Each button had up to seven values when working in different modes.
ZX Spectrum Computer
Image source
The internal architecture of the ZX Spectrum was also quite simple.
Thanks to the use of ULA (Uncommitted Logic Array) technology, the main part of the computer's circuit was placed on a single chip.
The Zilog Z80 with a clock frequency of 3.5 MHz was used as the central processor.
The amount of RAM was 16 or 48 Kbytes.
However, some third party manufacturers produced 32 KB memory modules that were inserted into one of the Spectrum expansion ports.
The volume of the ROM was 16 KB, and a dialect of the BASIC language called Sinclair BASIC was sewn into the memory.
The ZX Spectrum supported the output of only one bit audio through the built in speaker.
The computer worked only in graphic mode (8 colors and 2 brightness levels).
Therefore, there was no support for text mode.
The maximum resolution was 256x192 pixels.
The initial price for the ZX Spectrum was set at around 125 pounds.
Interestingly, Sinclair Research was still selling their devices via mail.
In the first 17 months after the release of Spectrum, more than a million computers were sold.
Unlike Western Europe, where other computers (the same Atari and Commodore) were sold perfectly along with the ZX Spectrum, in the USSR the Sinclair device was the sole sales leader.
Why?
The reason, first of all, was the low cost of the Spectrum: the computer was not subject to duties and was affordable for many Soviet citizens.
Atari and Commodore devices came a long way before they hit the shelves of Soviet stores, and their price was significantly higher compared to the ZX Spectrum.
In addition, it turned out that most of the Spectrum parts could be replaced with domestic ones if necessary.
Even the" secret " ULA chip was implemented on Soviet components.
As you may have guessed, the only irreplaceable component of the system was only the Z80 processor.
As a result, many Spectrum clones with domestic components appeared in the USSR: "Lviv 48", "Moscow 48", "Pentagon 48" and others.
In addition, a good part of the replicas were created by the radio amateurs themselves, independently.
A clone of "Spectrum" - Leningrad 48.
Inside view
Image source
The popularity of the ZX Spectrum was played into the hands of a huge number of different programs and games.
The computer was also quite convenient for learning programming.
Therefore, it is believed that a whole generation of domestic programmers has grown up on the Spectrum.
In the 90s, the ZX Spectrum platform reached the peak of popularity in the post Soviet space.
By this time, the computer had already lost its relevance in the West, and domestic enthusiasts were still creating improved clones of the Spectrum.
Nevertheless, new computers appeared on sale, and the ZX Spectrum began to gradually fade into the background.
Motorola 6800
Do not think that Intel had no competitors.
For example, Motorola actively promoted its 6800 processor.
The development of the chip began in 1969 under the leadership of engineer Tom Bennett, and, just like the 8080, Motorola's "stone" was released in 1974.
The crystal was produced according to a 6 micron process technology, and its clock frequency was the same 2 MHz.
Interestingly, the production of the 6800 also used the N MOS technology.
DIP40 was used as a form factor, and the processor instruction set contained 78 instructions.
Note that the 6800 had a 16 bit address bus with direct addressing of 64 Kbytes of memory.
Motorola 6800 processor
Image source
The processor was used in a huge number of personal computers.
Among them were the development boards MEK6800D2, SWTPC 6800, and computers Ohio Scientific, Midwest Scientific and Smoke Signal Broadcasting, as well as the MITS Altair 680 solution.
The latter was a complete analogue of the Altair 8800 system.
As you may have guessed, the only exception was that the 6800 processor was used instead of the 8080.
On the basis of the Motorola solution, several micro controllers that were used in industrial robots and some personal computers.
For example, the 6801 chip included, in addition to the processor, 2 KB of ROM, 128 bytes of RAM and supported hardware implemented multiplication.
Like Intel, Motorola provided licenses for the production of 6800 clones to third party companies.
Therefore, copies of the processor from Freescale and Hitachi appeared on the market, supporting a richer set of functions.
For example, they worked with an extended set of commands.
MOS Technology 6502 processor
At the same time, things were not going so smoothly inside the company.
And in 1974, the full development team of the 6800 processor joined the MOS Technology company.
Immediately, work began on a chip similar in architecture to the Motorola solution.
And in 1975, the 6501 processor saw the light.
However, sales of the "stone" were discontinued shortly after its announcement.
The reason for this was Motorola's lawsuit against MOS Technology due to the compatibility of the 6501 processor with 6800 based systems.
It took several more months before an updated version of the MOS Technology device with the index 6502 went on sale.
The characteristics of this chip were much more modest than those of the Intel 8080 and Motorola 6800.
The "Five Hundred and Second" was an 8 bit processor with a 16 bit address bus with support for addressing up to 64 KB of RAM.
Its clock frequency was only 1 MHz, but due to improved memory addressing methods and short instruction execution cycles, it was not so much inferior in performance to competing solutions.
Like all processors of the 70s, the 6502 had a CISC architecture, but some crystal addressing modes were later characteristic of RISC architectures.
MOS Technology 6502 processor
Image source
The main distinguishing feature of the processor was its price.
It was only $ 25, while the Intel 8080 and Motorola 6800 models were sold at a price of at least $ 180.
This forced the companies to reduce the prices of their devices, but it was already too late — sales of the 6502 were only growing.
MOS Technology managed to achieve such a low cost of the CPU due to the use of mask correction technology.
The masks themselves were large images of the layers of the chip crystal, which were subsequently reduced using a photographic process to obtain layers of the desired size.
Absolutely all masks had inaccuracies.
These inaccuracies were often duplicated on the crystal, which is why about 70% of the chips produced simply turned out to be non working.
MOS Technology has found a way to correct flaws in the masks, which allowed to significantly increase the percentage of output of working crystals, and therefore significantly reduce the cost of each chip.
So, the number of 6502 working crystals from their total number was already about 70%.
In addition to the main version of the processor, many modifications were released, which received indexes from 6503 to 6507.
Some of them have had the number of functions reduced in order to make it even cheaper.
MOS Technology distributed licenses for the production of 6502 processors.
As a result, companies such as Rockwell International, GTE, Synertek were engaged in the production of clones.
There was also a Soviet analogue of the 8502 called 4K602VM1.
Another domestic "stone" — 4K602VM1
6502 has found application in a huge number of personal computers.
For example, the processor was used in Apple I, Apple II and Commodore PET computers.
The 6502 also served as the basis for the Atari and BBC Micro home desktops line.
In addition, the development of MOS Technology was also used in the Atari 2600 and Nintendo Famicom video game consoles.
Instead of a conclusion
In the first half of the 1970s, the processor market was just beginning to gain momentum.
Intel was already getting into the leading positions at that time, Motorola was trying to keep up, and MOS Technology for a couple of Zilog pleasantly surprised and did not let the first two relax.
Recall that today we talked only about 4 and 8 bit processors, but in the second half of the 1970s, interesting 16 bit architectures appeared, which we will talk about next time.
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