History - Microprocessors (continued).

<b>History</b> - Microprocessors (continued).

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             Microprocessors
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                (C) Mark Heretz, Byte'85

                (C) Viper'99


                        ... Back to No.7



            Zapped 8080


  In April 1974, the firm Intel has forced us to forever change 
the prevailing understanding of computers.

The firm announced the creation of the microprocessor 8080 - 
much better than the processor 8008. Microprocessor 8080 
claimed a total of six chips support, served 75 teams, had ten 
times more capacity compared with 8008 and addressed to 64 
kilobytes of memory (no program, thought most of the time, can 
not be so big!).


  The project was proposed by the microprocessor 8080 
Fadzhinom, but the development team Masatoshi headed by Sima, a 
young engineer, whose firm lured from Intel Company Busycom. 
Taking into account the inconvenience and limitations of 
processors 4004 and 8008, developers have tried the new 
microprocessor improve the draft so that

A new chip has a really useful computing element.

  Intel 8080 - the first microprocessor,
purpose of which was not easy to change
logic. This microprocessor is more like a calculating machine 
than anything that were before him, and in terms of equipment 
was much easier to use. 

  In the January issue of the magazine "Popular
Electronics "for 1975 on the front pages was placed first in a 
series of articles devoted to the construction of the computer 
the Altair 8800, the so-called mini-car, built on the basis of 
the microprocessor 8080. Computer Altair was developed by MIT

(Micro Instrumentation and Telemetry
systems), which was founded by Ed Roberts to support and ensure 
its experiments in the field of electronics.

The whole set for the construction of Altair, including
microprocessor 8080, a motherboard,
power supply, front panel with lots of lights and 256 bytes 
(not 256 kilobytes) of memory on sale for $ 395. 

  At first we all thought that it was a typo. Chip containing 
the processor 8080, provided for only nine months before, one 
sold for 360 dollars. However, the price was a real

firm joined with MIT by Intel in the agreement. MIT firm sold 
the first day more computers than he had hoped to sell the 
entire life of this razrazbotki. 

  Altair computer played
significant role in that success, which
accompanied the microprocessor 8080, in
largely due to the fact that programmers now have the base and 
a good excuse to write software for a microprocessor chip. 
Except that developed for the machine Altair

open bus architecture (Advanced
version of which was the bus S-100) has allowed everyone to 
start developing peripherals for the computer. 

  One of these peripherals
a disk controller, developed by Digital Microsystems, which 
meant the beginning of the operating system for the 
microprocessor 8080 and called CP / M (Controlling Program for 
Microcomputers). Operating System CP / M, the brainchild of 
instructor High School Navy Harry Kildalla, sold for $ 70 and 
has played a major role in the success of the microprocessor 
8080 and its architecture. The result has been used at present

Day of software for microcomputers or works based on the 
commands processor 8080, either a direct

development of any system that
used this set of commands.

  In the microprocessor 8080 first applied n-MOS technology 
enrichment implemented decimal arithmetic and DDC,

use 16-bit address bus.


          The family of Motorola


  In response to the success of microprocessor 8080
firm Motorola has begun work on a processor 6800, a draft of 
which was designed by Chuck Peddy. Motorola was the first 
company, which introduced a series of chips for peripheral 
devices that are designed specifically for use with the 
microprocessor. Peripheral circuits include devices for 
parallel (chip 6820) and consistent (6850 chip) and I / O 
provided the inclusion of the input-output system

extremely easy for developers
systems properly.

  The developers have focused on the replacement logic 
microprocessors and minicomputers were needed, and 
cross-assemblers to create software, and

it has cost dearly. By that time, more
No one has posted anything to explain how to apply the new 
microprocessors, all those who know nothing about them inwards 
or had no experience with computers.


  Company MOS Technology published an advertisement, according 
to which the firm is going to present at the exhibition

WESCON in September of that year, and there
start selling 20-dollar microprocessor. The microprocessor 
company, received the name of 6501, was completely pin 
compatible with the 6800 processor chip company Motorola - you 
could vypayat of board microprocessor 6800,

inserted in its place 6501, and he began
to work. It is true that the software would still have to 
change, because there were some differences in the architecture 
of processors and their set of commands. MOS Technology Firm

also planned to release versions with built-in microprocessor 
clocking scheme, whose presence on a single chip, require all 
previously unreleased microprocessors. This version was 
obtained naimensovanie 6502 and cost $ 25. 

  All manufacturers of microprocessors
came to the excitement. While processors
Intel's 8080 and 6800 by Motorola
sold at a retail price of $ 179 apiece.

  On the first day of the fair commercial
representative of Intel said that
microprocessors will never be cheaper
$ 100. But even on that first day
WESCON'a from Intel and Motorola have been forced to reduce the 
price of its chips to 69 dollars 95 cents. The revolution was

at full speed, the electronics industry could no longer turn 
back. 

  Microprocessor 6501 was destined to a short life. 
Manufacturer Motorola filed against the MOS Technology case, 
alleging that Chuck Peddy stole technology from Motorola and 
the company that created the microprocessor 6501 with copyright 
infringement because it was interchangeable with its analog 
Motorola 6800. Company MOS Technology agreed to stop

output processor 6501.

  However, many computers,
built microprocessor-based
6502, have now become legend: private
development firm MOS Technology KIM-1,
Machine Apple I and Apple II, various models of Atari, as well 
as among other machines Commodore PET and VIC-20.



           The appearance Z80


  In late 1975, Federico Fadzhin left the firm Intel and 
founded the firm under called Zilog. In 1976, the firm Zilog

announced the creation of the microprocessor Z80,
significantly improved version of the microprocessor 8080, 
which included the entire instruction set of the latter and 
accordingly allowed to work matobespecheniyu written for the 
microprocessor 8080. Company also announced that there are 
microprocessors that run at a clock frequency of 4 MHz, ie 
twice processor 8080. In addition, the Z80 microprocessor to 
perform many additional teams - the total number of teams equal 
to 176. It was too good to seem true, and the microprocessor

Z80 was adopted with the same skepticism,
that of 6502 before that. However, the Z80 microprocessor was a 
reality, and indeed There were party processors who worked at a 
frequency of 4 MHz. 

  Several boards for a set of Z80 with the bus
S-100 appeared on the market immediately after
development of the microprocessor, and all at once
It took these boards. Nevertheless,
despite the fact that the microprocessor Z80
was much more powerful processor 8080
in the sense of a set of commands, at first very
few have ventured to write programs with
taking advantage of additional commands
Z80. The reason is simple: most
machines operating at that time were based on a microprocessor 
8080, and if you would write programs that can only run on the 
microprocessor Z80, then your market proved to be too

small.

  Nevertheless, the developers did not
apply the microprocessor 8080 in New
systems. Chip containing the processor Z80, was a much more 
easy to use, for it required only a single supply voltage, and 
thus do not need support chips. And this

the microprocessor much faster
even without additional
commands.

  Together with the Z80 microprocessor came
Another new principle of microcomputer
circuits: integrated regeneration scheme dinamichesksoy of RAM. 
Dynamic memory devices such as RAM is always worth about four 
times cheaper than their competitors static per 1 bit, and This 
makes them very attractive for use. However, due to the fact 
that must constantly regenerate a memory (otherwise it forgets 
its data), its use was extremely difficult. The presence in the 
microprocessor Z80 regeneration scheme of the heap was a very 
big step forward and possible to build systems that were

much cheaper than previous ones. Such a microcomputer as the 
TRS-80 Company Radio Shack, designed by Steve Leningerom used 
precisely this advantage of the processor.