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All Obzoryzhelezovse reviews of computer hardware
Topics: processor
The evolution of processors.
Part 2: The 16 bit Era
30.06.2014
Oleg Kolenchenko, info@ferra.ru
Print version
In the 1970s, central processing units developed very quickly.
First, 4 — bit crystals appeared, then 8 bit ones.
When they also revealed their potential, manufacturers took up the development of new 16 bit processors.
They will be discussed in this material.
Table of contents
Intel 8086/8088 and x86 architecture Intel 80186 and 80286 Motorola 68k and Apple computers DEC PDP 11 WDC W65C816S and Zilog Z8000 Instead of conclusion
In the first part of our material, we told you about the development of the industry in the 1940s and 1970s, as well as about the creation of the first microprocessors.
By the end of the seventies, the potential and performance of 8 bit chips reached their ceiling, and large companies began to develop and produce 16 bit solutions, which will be discussed later.
How legends were born
Image source
Intel 8086/8088 and x86 architecture
By the end of the 1970s, the market for 8 bit processors was crowded.
The crystals of Intel, Motorola and MOS Technology companies sold well.
The Zilog Z80 chip was considered particularly successful.
In addition, clones of these processors were distributed on sale, which often differed from the original models by significantly improved characteristics.
The development of 8 bit solutions has reached its limit, so major manufacturers have concentrated on the development of 16 and 32 bit "stones".
The development of the 16 bit Intel 8086 processor started in the spring of 1976.
At that time, the 8086 project was considered only an intermediate stage before the launch of the 32 bit iAPX 432 architecture of the same name.
The company had very high hopes for this chip, but at the same time they understood that the existing 8 bit processors would not be able to ensure a stable financial position of the company.
In addition, it was a matter of principle for Intel to shift the Zilog Z80, developed, as you already know, by Federico Fagin, from the leading positions.
Therefore, it was decided to develop a temporary replacement for the iAPX 432 in the face of the 8086 processor.
Intel 8086 processor
Image source
The development of the 8086 was entrusted to engineer Stephen Morse, who compiled the main specifications of the processor and its architecture by mid summer 1976.
It took Intel two more years to create it.
And on June 8, 1978, the crystal 8086 was officially announced.
The processor was produced according to a 3 micron process technology and contained 29,000 transistors.
Its clock frequency was from 4 to 10 MHz.
The bit depth of the registers and the data bus was 16 bits, and the bit depth of the address bus was 20 bits.
The amount of addressable memory was 1 MB.
The maximum heat dissipation of the 8086 was at the level of 1.75 watts.
A 40 pin DIP was used as a form factor.
During the development of the processor, Intel engineers did not set the task of backward compatibility at the 8086 software level with the previous 8 bit models, but most of the programs written for the 8080 crystal could be run on the "eighty sixth" after recompilation.
Stephen Morse (right) - the father of "eighty six"
Image source
The Intel 8086 was about 10 times faster than the 8080 index model.
The processor became the first implementation of the x86 instruction system and the architecture of the same name, which later became a kind of standard and is used in AMD and Intel crystals to this day.
However, at that time, Intel did not even suspect how successful their project would be.
Sales of the 8086 were very sluggish, and in 1979 the father of the "eighty sixth" Stephen Morse left the company.
The reason for the weak sales of new processors was that 16 bit support chips were needed for their operation.
At that time, the market was focused on the production of auxiliary chips for 8 bit processors, and 16 bit solutions were very expensive.
Therefore, most manufacturers still relied on budget 8 bit "stones".
To solve the problem and increase sales of the 8086, Intel went an interesting way.
In 1979, they released the 8088 processor.
The "eighty eighth" was a complete analog of the 8086 crystal, with the exception of the modified data bus.
Its width was cut from 16 bits to 8 bits, which allowed it to work with 8 bit support chips.
With one small change, Intel has finally set the stage for the use of its 16 bit processors.
Intel 8088 processor
Image source
The results were not long in coming.
At that time, IBM was just beginning to develop its subsequently very successful IBM 5150 computer.
It was decided to use only a 16 bit processor in the system, and IBM engineers had to choose between three models: Motorola 68000 (we will talk about it later), Intel 8086 and Intel 8088.
For IBM, Intel's "stones "were more familiar and convenient, so the choice was made in favor of the"eighty eighth".
In addition, simpler 8 bit support chips could be used to operate this processor, which allowed IBM to create cheaper computers.
Another advantage of Intel crystals was that Microsoft already had the BASIC programming language for 8088.
The development of the 5150 computer was of great importance for IBM.
In the second half of the 1970s, the personal desktop market was actively developing, and IBM did not pay enough attention to this segment.
Of course, the company was aware of all its prospects, and therefore it was decided to develop its own computer model.
The IBM 5150, the first model of the IBM PC line, was released in 1981.
The top version of the computer was estimated at $ 3005.
It was equipped with an Intel 8088 processor with a frequency of 4.77 MHz, and the amount of RAM was 64 Kbytes.
The IBM 5150 used 5.25 inch floppy disks as a data storage device.
And a little later, computer models appeared on sale that allowed using audio cassettes as a data storage.
It was impossible to install a hard disk into the system, but after a while IBM released a hard drive that connected to the 5150 as an expansion module.
The computer had several expansion ports, through which, in addition to the hard drive, video adapters, cards with I / O ports and other devices were connected.
The younger version of the desktop cost almost half as much — 1565 US dollars.
The" stripped down " model used the same Intel 8088, but the amount of RAM was only 16 KB.
Secondly, unlike the older version, the younger one was not equipped with a CGA monitor and a floppy disk drive.
It was proposed to use a TV as a display, and it was possible to store data on a cassette drive.
Also, unlike the top end version of the IBM 5150, the younger model did not work with the PC DOS 1.0 operating system (which later became MS DOS).
IBM 5150 computer
Image source
Not to say that the success of the first IBM PC was stunning.
Yes, the computer sold well, but no more.
At that time, it was possible to buy a personal computer at a lower price and with better characteristics than IBM.
Often, the IBM brand itself played into the hands of sales — everyone knew it.
In March 1983, the company introduced an updated version of the 5150 called IBM PC/XT.
The computer was based on the same 8088 processor, but at the same time it introduced many changes.
So, a full fledged hard disk with a 10 MB ST 412 interface was finally added to the computer, and the RAM capacity was 128 KB or 256 KB.
The computer was equipped with a monochrome MDA video adapter or a 16 color CGA.
After some time, it became possible to use the EGA adapter in the system.
As for the operating system, the IBM PC/XT used PC DOS version 2.0.
Externally, the IBM PC/XT was not much different from the 5150
Image source
Interestingly, IBM did not protect the architecture of the PC computer with copyrights, and therefore a huge number of clones of this model appeared on the market, which also used the 8088 processor.
Intel only benefited from this state of affairs.
It is worth noting that the 8088 processor itself also had many clones.
Such large companies as AMD, Siemens, NEC and others were engaged in their production.
Intel 80186 and 80286
Immediately after the end of the development of the 8086, Intel engineers started a new project — the 80186 processor.
This chip was based on the same architecture.
As you know, the main disadvantage of the 8086 was the need to use numerous support chips, so it was decided to abandon them in the 80186.
All the necessary components were transferred to the processor itself.
Thus, the 80186 architecture already included two direct memory access controllers with interrupt circuits( DMA), address decoders, a three channel programmable timer counter, a synchronization generator and a programmable interrupt controller.
In addition, the system of internal instructions has been significantly expanded.
Additional commands for working with the stack and I / O ports were added, new arithmetic commands and commands for implementing high level languages appeared.
Intel 80186 processor
Image source
As for the technical characteristics of the processor, here it was not surprised by anything.
The crystal, like the 8086, was produced according to a 3 micron process technology and contained 134,000 transistors.
The bit depth of the registers and the data bus was 16 bits, the address bus was 20 bits.
The amount of addressable memory was still 1 MB.
The clock frequencies ranged from 6 to 25 MHz.
Due to the significantly redesigned architecture, the 80186 could not be used on IBM PC compatible computers, which is why it was very rarely found in computers of that time.
Among the few models that use this "stone" are the world's first laptop Dulmont Magnum, Mindset computers, Siemens PC D, HP 100/200LX, HP 1000CX, Compis and RM Nimbus school desktops, as well as some other devices.
Dulmont Magnum
Image source
Intel's next step was to launch a processor with the 80286 index.
It was developed in parallel with the 80186, so it can also be considered a redesigned "eighty sixth", on the architecture of which it was based.
The 80286, as well as the 80186, was introduced in 1982.
If we compare the architectures of these processors, we can see that the "two hundred and eighty sixth" lacked some of the built in modules that were available in the 80186.
In addition, the 80286 was distinguished by an increased number of registers.
New instructions were added to the crystal, as well as a protected mode of operation of the "stone".
Intel 80286 processor
Image source
Let's say a few words about the operating modes of the processor.
In addition to the protected mode, 80286 also supported the real one.
In it, the crystal was fully compatible with other processors with the x86 architecture.
Simply put, it ran programs designed for the 8086 and 8088.
At the same time, the amount of addressable memory was 1 MB.
In protected mode, the address space capacity could be up to 1 GB due to a change in the memory addressing mechanism.
Thus, only the part of the program that was needed at the moment was stored in memory.
And in the case of accessing the part that was not stored in memory, the operating system suspended the program, loaded the necessary pieces of code and continued its execution.
Despite the support of protected mode, it was used extremely rarely and very limited by the processor.
Now let's talk about the technical characteristics of the device.
First of all, it is worth noting that 80286 became the first Intel "stone", produced according to 1.5 microns technological standards.
The number of processor transistors was 134,000 pieces.
The clock frequency depended on the model and was equal to 6 MHz, 8 MHz, 10 MHz or 12.5 MHz, respectively.
The bit depth of the registers and the data bus was 16 bits, and the address bus was 24 bits.
As we have already said, the amount of addressable memory was 16 MB, although up to 1 GB of virtual memory could be used in protected mode.
The efficiency of the processor was very high.
At a frequency of 12.5 MHz, the 80286 model performed at least 2.66 million operations per second.
For comparison, the 8086 with a frequency of 10 MHz had a performance of about 0.75 million operations per second.
As before, Intel provided licenses for the production of 80286 clones to third party manufacturers.
IBM PC/AT computer
Image source
The main application for the 80286 model was IBM PC/AT computers — the third model in the IBM PC line.
And the most successful.
Unlike its predecessors in the face of the IBM PC and PC/XT, which used an 8088 processor, the PC/AT was equipped with an 80286 chip with a frequency of 6 or 8 MHz.
A special feature of the computer was the use of a 16 bit AT bus input / output bus.
Its use allowed to increase the maximum amount of RAM to 16 MB.
For example, IBM PC and PC/XT worked only with RAM up to 640 Kbytes.
A battery for powering a 50 byte CMOS chip appeared on the computer's motherboard.
Previously, it was not available in IBM PC systems.
5.25 inch floppy disks with a capacity of 1.2 MB were still used as data storage, while IBM PC and PC/XT computers supported only floppy disks with a volume of up to 360 KB.
The PC/AT graphics system was represented by an EGA or PGA video adapter.
Later models of the IBM PC/AT were already equipped exclusively with a VGA video adapter.
For all the innovations to work, a different operating system was required — PC DOS 3.0.
IBM PC/AT has become truly successful.
It further strengthened the leading positions of IBM and the x86 architecture in the computer market.
Motorola 68k and Apple computers
Intel's 16 bit processors did not dominate the market, despite the growing popularity of the IBM PC line.
The main competitor of the "Intel" crystals was the Motorola 68000 series of processors.
The Motorola 68k project started in 1976 — the same year when the development of the 16 bit Intel 8086 processor began.
Initially, the 68k family was considered as chips with a completely new architecture.
So, there was no question of any backward compatibility with 8 bit Motorola 6800 processors.
However, looking ahead, let's say that the Motorola 68000 crystals still received support for the "stones" bus protocol of the previous generation.
The development bet was made on something else — Motorola wanted to ensure backward compatibility of subsequent developments with the 68k family.
In short, we wanted to create an architecture that would become the basis for processors for many years to come.
Motorola 68000 processor
Image source
The Motorola 68000 line was introduced in 1979.
The processors were based on the CISC design, and many architectural features were borrowed from the PDP 11 computer.
The Motorola 68000 cannot be unambiguously attributed to the category of 16 or 32 bit devices.
Although the crystal had a 32 bit core, it worked via 16 bit data buses.
Motorola turned out to be a kind of hybrid.
It goes without saying that the Motorola 68000 processor had a completely different command system than processors with the x86 architecture.
The instruction set of the crystal is considered more "orthogonal" than x86.
This means that operations and operands can be freely combined, without paying attention to the limitations associated with the compatibility of a particular operation and a set of operands.
The advantage of this approach is the ease of programming in the Motorola 68000 assembler.
As for other technical characteristics, as we have already said, the Motorola 68000 worked with a 16 bit data bus and a 24 bit address bus.
Its frequency ranged from 8 MHz to 20 MHz, and the number of transistors was 68,000 pieces.
The chip was produced in the DIP form factor with 64 pins, but there were also models with LCC and PGA connectors.
Three years later, Motorola released the next model of the 68k line — the Motorola MC68010 processor.
Oddly enough, the crystal turned out to be incompatible with the 68000 model at the software level.
At the same time, the processor has not made any revolutions in design.
The main differences between the "tenth" and the crystal with the index 68000 were working with virtual memory and adding a new VBR (vector base register) register.
Motorola MC68010 processor
Image source
If we talk about the technical characteristics, they almost completely corresponded to those of the Motorola 68000.
The changes affected only the number of transistors, which became 84,000.
Nevertheless, the 68010 model turned out to be about 10% faster than the 68000.
In comparison with its predecessor, the new processor did not gain much success.
Only thanks to the support for working with virtual memory, some manufacturers used the chip in small UNIX systems, for example, Sun 2 Workstation and AT&T UNIX PC.
The market was waiting for the second generation of Motorola 68k.
The Motorola 68000 processor was used in many computers, but many people remember it from the first Apple computers.
So, different versions of this "stone" were used in the first Apple personal computers: Lisa and Macintosh.
Apple Lisa appeared in 1983.
It took almost 5 years to develop the computer.
As you know, the project was launched back in 1978.
Apple wanted to create a computer that would combine all the components in one case.
The technical part of Lisa was also innovative.
Protected memory, cooperative multitasking, a complex file system, data breach protection systems, support for up to 2 MB of RAM and a high resolution screen were implemented in the desktop.
But the project was expected to be a commercial failure.
The main reason for the low sales of Lisa was its high cost — $ 10,000.
Few people could afford to buy such a computer at home.
Apple Lisa Computer
Image source
In parallel with Lisa, another computer was being developed — the Macintosh.
The project started in 1979, and in 1981 it was headed by Steve Jobs.
The computer itself was released in 1984.
The principle of creating a Macintosh was quite simple: take the best from Lisa, but at the same time make the computer as simple and accessible as possible.
The desktop received the same Motorola 68000 processor, but its frequency was increased to 8 MHz.
The amount of RAM was 128 Kbytes.
The design of the "Macintosh" provided for a built in 9 inch black and white screen with a resolution of 512x342 pixels.
A 3.5 inch floppy disk with a volume of 400 KB was used as a data storage.
The computer was also equipped with a mouse and keyboard.
The cost of the Macintosh was $ 2,500, which was significantly lower than the cost of the Lisa.
Despite the fact that the Apple computer cost more than the IBM PC models, it was not only able to compete with a decent competition, but also become a full fledged th alternative.
In short, the release of "Macintosh" marked the beginning of a great confrontation between Apple and IBM.
Apple Macintosh 128k
Image source
In addition to Apple computers, the Motorola 68000 processor was also used in other devices: for example, in high performance Texas Instruments calculators and Commodore Amiga, Sinclair QL and Atari ST desktops.
DEC PDP 11
Despite the fact that the 80s were marked by the dominance of IBM and Apple computers, we should not forget about PDP computers and specifically about the PDP 11 model, which had a great influence on the architecture of Motorola processors.
Many consider it one of the greatest desktops of all time.
The PDP 11 was the world's first 16 bit system.
It became available much earlier than the IBM PC and Apple Macintosh, and went on sale in 1970.
Like all processors of that time, the PDP 11 was based on the CISC architecture.
Its main difference was the "orthogonal" command system, which was used for the first time.
Many modifications of the PDP 11 did not have a separate I / O bus, but only a Unibus memory bus.
PDP 11 Computer Panel
Image source
The Unibus bus itself is the first computer bus.
It was completely asynchronous, which allowed you to simultaneously connect fast and slow devices.
A little later, a bus for magnetic disks and tapes called Massbus was added to the PDP 11.
There were also models of a computer with a Q Bus interface, which was a cheaper version of Unibus and used multiplexing, allowing data lines and addresses to use the same contacts.
At the same time, the bus functionality was practically not reduced: Q Bus supported I / O with memory mapping (the same protocol is used for data exchange between any devices over the bus), addressing with byte accuracy and an asynchronous interaction protocol.
The technical component of the PDP 11 was constantly improving, and over time, the Unibus and Q Bus buses simply began to limit the computer's potential.
In addition, 16 bit addressing did not allow creating large programs.
As a result, the PDP 11 computer could not compete with the IBM PC computers that were just gaining momentum.
WDC W65C816S and Zilog Z8000
Western Design Center (WDC) and Zilog have released their 16 bit processors.
The first introduced its W65C816S crystal only in 1984.
At the same time, the processor did not stand out from its competitors in any way.
Moreover, it, in fact, was only an improved version of the 8 bit WDC 65C02 chip, which, in turn, was a clone of the 8 bit MOS Technology 6502 crystal.
WDC W65C816S processor
Image source
Interestingly, the WDC W65C816S was developed by order of Apple.
The Apple company needed a processor for the updated Apple II series of computers, which could provide backward compatibility with the 65C02, which was used in the initial Apple II line.
This is how the W65C816S appeared.
It did not have any architectural features.
The processor worked with 16 bit registers, supported 24 bit memory addressing and a 16 bit stack pointer, and also had an extended set of instructions.
A little later, a static core appeared in the W65C816S, which allowed storing register data without receiving a clock signal.
Coupled with the use of static memory with random access, this allowed the "stone" to consume a minimum amount of energy when switching to sleep mode.
The processor found its application in the Apple IIGS computer, as well as the Acorn Communicator and C One systems.
Zilog also introduced a follower of the successful Z80 processor — the 16 bit Z8000 crystal.
It was not backward compatible with the "eighties" chip and, in general, could not repeat the success of its predecessor.
Initially, two versions of the processor were released: Z8001 and Z8002.
Their differences consisted only in the fact that the first worked with addressing up to 8 MB of memory, and the second only up to 64 KB.
A little later, the Z8003 and Z8004 models appeared, which were able to work with virtual memory.
All processors supported an orthogonal command system.
As for the clock frequency of the Z8000, it ranged from 4 to 10 MHz.
Zilog Z8000 processor
Image source
The Z8000 was often used in UNIX desktop computers, which allowed creating real multi user systems.
It could also be found in computers such as the Onyx C8000, Olivetti M and Commodore 900.
The Z8000 was introduced simultaneously with Intel 8086 and Motorola 68000 processors, but it could not compete with them properly.
Instead of a conclusion
We have told you about how things were going by the mid 1980s.
Two leaders have been identified among processor manufacturers: Intel and Motorola.
At the same time, IBM and Apple began to struggle in the segment of ready made computers.
This is the end of the short period of 16 bit processors.
The next step was the launch of 32 bit crystals.
But read about this in the next part of our series of materials.
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