Specifications

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of all today’s microprocessors. Intel kept on developing it and in April 1974 it launched an 8-bit processor called the 8080. It was able to address
64Kb of memory, had 75 instructions and initial price was $360.
Another American company called Motorola, quickly realized what was going on, so they launched 8-bit microprocessor 6800. Their chief
constructor was Chuck Peddle. Apart from the processor itself, Motorola was the first company that also manufactured other peripherals such as
the 6820 and 6850. At that time many companies recognized the greater importance of microprocessors and began their own development. Chuck
Peddle left Motorola to join MOS Technology and kept working intensively on developing microprocessors.
At the WESCON exhibition in the USA in 1975, a crucial event in the history of the microprocessors took place. MOS Technology announced that it
was selling processors 6501 and 6502 at $25 each, that interested customers could purchase immediately. It was such a sensation that many
thought it was a kind of fraud, considering that competing companies were selling the 8080 and 6800 at $179 each. On the first day of the
exhibit, in response to the competitor, both Motorola and Intel cut the prices of their microprocessors to $69.95. Motorola accused MOS
Technology and Chuck Peddle of plagiarizing the protected 6800. Because of that, MOS Technology gave up further manufacture of the 6501, but
kept manufacturing the 6502. It was the 8-bit microprocessor with 56 instructions and ability to directly address 64Kb of memory. Due to low
price, 6502 became very popular so it was installed into computers such as KIM-1, Apple I, Apple II, Atari, Commodore, Acorn, Oric, Galeb, Orao,
Ultra and many others. Soon several companies began manufacturing the 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, Commodore took over MOS
Technology). In the year of its prosperity 1982, this processor was being sold at a rate of 15 million processors per year!
Other companies did not want to give up either. Frederico Faggin left Intel and started his own company Zilog Inc. In 1976 Zilog announced the
Z80. When designing this microprocessor Faggin made a crucial decision. The 8080 had already been developed and he realized that many would
remain loyal to that processor because of the great expenditures which rewriting of all the programs would result in. Accordingly he decided that
a new processor had to be compatible with the 8080, i.e. it had to be able to perform all the programs written for the 8080. Apart from that,
many other features have been added so that the Z80 was the most powerful microprocessor at that time. It was able to directly address 64Kb of
memory, had 176 instructions, a large number of registers, a built-in option for refreshing dynamic RAM memory, a single power supply, greater
operating speed etc. The Z80 was a great success and everybody replaced the 8080 by the Z80. Certainly the Z80 was commercially the most
successful 8-bit microprocessor at that time. Besides Zilog, other new manufacturers such as Mostek, NEC, SHARP and SGS appeared soon. The
Z80 was the heart of many computers such as: Spectrum, Partner, TRS703, Z-3 and Galaxy.
In 1976 Intel came up with an upgraded version of the 8-bit microprocessor called the 8085. However, the Z80 was so much better that Intel lost
the battle. Even though a few more microprocessors appeared later on the market (6809, 2650, SC/MP etc.), the die had already been cast.
There were no such great improvements which could make manufacturers to change their mind, so the 6502 and Z80 along with the 6800
remained chief representatives of the 8-bit microprocessors of that time.
Microcontroller versus Microprocessor
A microcontroller differs from a microprocessor in many ways. The first and most important difference is its functionality. In order that the
microprocessor may be used, other components such as memory must be added to it. Even though the microprocessors are considered to be
powerful computing machines, their weak point is that they are not adjusted to communicating to peripheral equipment.
Simply, In order to communicate with peripheral environment, the microprocessor must use specialized circuits added as external chips. In short
microprocessors are the pure heart of the computers. This is how it was in the beginning and remains the same today.
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