Although the 8080 was generally an 8-bit processor, it also had limited abilities to perform 16-bit operations: Any of the three 16-bit register pairs ( BC, DE, HL ) or SP could be loaded with an immediate 16-bit value ( using LXI ), incremented or decremented ( using INX and DCX ), or added to HL ( using DAD ).

The Z80 came about when Federico Faggin, after working on the 8080, left Intel at the end of 1974 to found Zilog with Ralph Ungermann, and by July 1976 they had the Z80 on the market.

** Non-multiplexed buses ( the 8080 had state-signals multiplexed onto the data bus )

On most machines the " bootstrap " was a minimal bootloader in ROM combined with some means of minimal bank switching or a means of injecting code on the bus ( since the 8080 needs to see boot code at Address 0 for start-up, while CP / M needs RAM there ); for others, this bootstrap had to be entered into memory using front panel controls each time the system was started.

The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP / M operating system ; it had 8-bit data words and 16-bit addresses.

Initially, bus implementations were proprietary ( such as the Apple II and Macintosh ), but by the late 1970s manufacturers of Intel 8080 / Zilog Z80-based computers running CP / M had settled around the S-100 standard.

The original development system had an 8080 processor.

The 56-pin STD Bus (" STD-80 bus "); used signals of the Z80, which had soon replaced the 8080.

The 6800 had a minimum clock rate of 100 kHz while the 8080 could be halted.

The Z80-CPU had a substantially better bus structure and interrupt structure than the 8080 and could interface directly with dynamic RAM, since it included an internal memory-refresh controller.

The Altair 8800, based on the Intel 8080 microprocessor, only had 256 bytes of memory, but it struck a chord with so many hackers that MITS went from being close to bankruptcy to having millions of dollars worth of orders, and being unable to fulfill the orders in time.

Intel had announced the 8080 chip, and compared to the 4004 to which IMS Associates had been first introduced, the 8080 looked like a " real computer ".

Program text, variables, disk buffers and the CP / M operating system itself all had to share the 64 kilobyte address space of the 8080 processor.

It had a NEC V20 CPU ( an enhanced Intel 8088 clone with Intel 80186 instruction set compatibility and an additional Intel 8080 emulation mode, running at 5. 37 MHz ), but was hampered in running PC applications because of its quarter-CGA resolution LCD screen and MDA compatible ( instead of CGA ) graphics chip.

It had a Tesla MHB8080A ( copy of Intel 8080 ) CPU / 2 MHz, 32 KB RAM ( later on 64 KB ), 4 KB ROM, with video output and the BASIC programming language as external modules.

As in the 8080, the contents of the memory address pointed to by HL could be accessed as pseudoregister M. It also has a 16-bit stack pointer to memory ( replacing the 8008's internal stack ) This register is always decremented / incremented by 2 during push and pop and a 16-bit program counter.

The first commercial PC, the Altair 8800 ( by MITS ), used an Intel 8080 CPU with a clock rate of 2 MHz ( 2 million cycles / second ).

It featured 2. 048 MHz Intel 8080 CPU, 48 KiB RAM, 8 KiB ROM with built-in BASIC, good keyboard ( compared with PMD 85 ), monitor video output ( but not TV output ) with 288 × 256 resolution, 4 colours.

The first three models, Smaky 1, Smaky 2, and Smaky 4, were based on the Intel 8080 microprocessor ( Smaky 3 was a prototype that was never completed ).

An improvement over the 8080 was that the 8085 can itself drive a piezoelectric crystal directly connected to it, and a built in clock generator generates the internal high amplitude two-phase clock signals at half the crystal frequency ( a 6. 14 MHz crystal would yield a 3. 07 MHz clock, for instance ).

It was based on the MHB 8080A CPU ( a Tesla clone of the Intel 8080 ), clocked at 1. 111 MHz.

** Single-phase 5 V clock ( the 8080 needed a two-phase high-amplitude clock generator )

The 8080 require more clock cycles to execute a processor instruction.

By comparison, the MOS Technology 6502 takes two to seven clock cycles to execute an instruction, and the Intel 8080 takes 4 to 18 clock cycles.

Since the introduction of the first commercially available microprocessor ( the Intel 4004 ) in 1970, and the first widely used microprocessor ( the Intel 8080 ) in 1974, this class of CPUs has almost completely overtaken all other central processing unit implementation methods.

However, the 8086 design was expanded to support full 16-bit processing, instead of the fairly basic 16-bit capabilities of the 8080 / 8085.

The Intel 4004 was a 4-bit processor released in 1971, but in 1973 the Intel 8080, an 8-bit processor, made the first personal computer, the Altair 8800, possible.

FORTH, Inc .' s microFORTH was developed for the Intel 8080, Motorola 6800, and Zilog Z80 microprocessors starting in 1976.

The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974.

The 8080 was implemented using non-saturated enhancement-load NMOS, demanding an extra + 12 volt and a − 5 volt supply.

The Intel 8080 was the successor to the 8008.

However, in some simple 8080 computers, I / O was indeed addressed as if they were memory cells, " memory mapped ", leaving the I / O commands unused.

The 8080 device, often described as the first truly useful microprocessor, was eventually replaced by the depletion-load based 8085 ( 1977 ) which could cope with a single 5V power supply instead of the three different operating voltages of earlier chips.

Marketed as source compatible, the 8086 was designed to allow assembly language for the 8008, 8080, or 8085 to be automatically converted into equivalent ( sub-optimal ) 8086 source code, with little or no hand-editing.

The programming model and instruction set was ( loosely ) based on the 8080 in order to make this possible.

It outperformed the more complex 6800 and Intel 8080, but cost much less and was easier to work with.

The 8086 was introduced during 1978 as a fully 16-bit extension of Intel's 8-bit based 8080 microprocessor and also introduced memory segmentation to overcome the 16-bit addressing barrier of such designs.

It was designed to be binary compatible with the Intel 8080 so that most 8080 code, notably the CP / M operating system, would run unmodified on it.

At about the same time, the new assembly language was also extended to accommodate the added addressing possibilities in the more advanced Intel 8080 chip ( the 8008 and 8080 shared a language subset without being binary compatible ; however, the 8008 was binary compatible with the Datapoint 2200 ).

CP / M ( Control Program / Monitor ) was a mass-market operating system created for Intel 8080 / 85 based microcomputers by Gary Kildall of Digital Research, Inc.

The only hardware system that CP / M, as sold by Digital Research, would support was the Intel 8080 Development System.

CP / M would also run on systems based on the Zilog Z80 processor since the Z80 was compatible with 8080 code.