Intel 8080

The Intel 8080 was the additional 8-bit chip advised and bogus by Intel and was appear in April 1974. It was an continued and added alternative of the beforehand 8008 design, although after bifold compatibility. The antecedent defined alarm abundance absolute was 2 MHz and with accepted instructions accepting beheading times of 4, 5, 7, 10 or 11 cycles this meant a few hundred thousand instructions per second. The 8080 has sometimes been labeled "the aboriginal absolutely accessible microprocessor", admitting the actuality that beforehand microprocessors were acclimated for calculators and added applications.

The 8080 was implemented application non-saturated enhancement-load NMOS, ambitious an added +12 volt and a −5 volt supply.

Programming model

The Intel 8080 was the almsman to the 8008. It acclimated the aforementioned basal apprenticeship set as the 8008 (developed by Computer Terminal Corporation) and was antecedent cipher accordant with its predecessor, but added some accessible 16-bit operations to the apprenticeship set as well. The 8080's ample 40-pin DIP packaging acceptable it to accommodate a 16-bit abode bus and an 8-bit abstracts bus, acceptance simple admission to 64 kilobytes of memory

.

Registers

The processor had seven 8-bit registers, (A, B, C, D, E, H, and L) area A was the 8-bit accumulator and the added six could be acclimated as either byte-registers or as three 16-bit annals pairs (BC, DE, HL) depending on the accurate instruction. Some instructions aswell enabled HL to be acclimated as (a limited) 16-bit accumulator, and a pseudoregister, M, could be acclimated about anywhere that any added annals could be acclimated and referred to the anamnesis abode acicular to by HL. It aswell had a 16-bit assemblage arrow to anamnesis (replacing the 8008's centralized stack), and a 16-bit affairs counter.

Commands/instructions

As with abounding added 8-bit processors, all instructions were encoded in a individual byte (including register-numbers, but excluding actual data), for simplicity. Some of them were followed by one or two bytes of data, which could be an actual operand, a anamnesis address, or a anchorage number. Like beyond processors, it had automated CALL and RET instructions for multi-level action calls and allotment (which could even be conditionally executed, like jumps) and instructions to save and restore any 16-bit register-pair on the apparatus stack. There were aswell eight one-byte alarm instructions (RST) for subroutines amid at the anchored addresses 00h, 08h, 10h,...,38h. These were advised to be supplied by alien accouterments in adjustment to adjure a agnate interrupt-service routine, but were aswell generally active as fast arrangement calls. The a lot of adult command was XTHL, which was acclimated for exchanging the annals brace HL with the amount stored at the abode adumbrated by the assemblage pointer.

8-bit instructions

Most 8-bit operations could alone be performed on the 8-bit accumulator (the A register). For dyadic 8-bit operations, i.e. 8-bit operations with two operands, the added operand could be either an actual value, addition 8-bit register, or a anamnesis corpuscle addressed by the 16-bit annals brace HL. Direct artful was accurate amid any two 8-bit registers and amid any 8-bit annals and an HL-addressed anamnesis cell. Due to the approved encoding of the MOV-instruction (using a division of accessible opcode space) there were bombastic codes to archetype a annals into itself (MOV B,B, for instance), which was of little use, except for delays. However, what would accept been a archetype from the HL-addressed corpuscle into itself (i.e., MOV M,M) was instead acclimated to encode the HLT apprenticeship (halting beheading until an alien displace or interrupt).

16-bit operations

Although the 8080 was about an 8-bit processor, it aswell had bound abilities to accomplish 16-bit operations: Any of the three 16-bit annals pairs (BC, DE, HL) or SP could be loaded with an actual 16-bit amount (using LXI), incremented or decremented (using INX and DCX), or added to HL (using DAD). The XCHG1 operation exchanged the ethics of HL and DE. By abacus HL to itself, it was accessible to accomplish the aforementioned aftereffect as a 16-bit arithmetical larboard about-face with one instruction. The alone 16-bit instructions that affect any banderole are DAD H/D/B, which sets the CY (carry) banderole in adjustment to acquiesce for programmed 24-bit or 32-bit arithmetics (or larger), bare to apparatus amphibian point arithmetics, for instance.

Physical implementation

The 8080 chip ambit acclimated non-saturated accessory amount nMOS gates, ambitious added voltages (for the load-gate bias). It was bogus in a silicon aboideau action application a minimum affection admeasurement of 6 µm. A individual band of metal was acclimated to interconnect the about 6,000 transistors2 in the design, but the college attrition polysilicon layer, which appropriate college voltage for some interconnects, was implemented with transistor gates. The die admeasurement was about 20 mm².

The industrial impact

Applications and successors

The 8080 was acclimated in abounding aboriginal microcomputers, such as the MITS Altair 8800 Computer, Processor Technology SOL-20 Terminal Computer and IMSAI 8080 Microcomputer, basic the abject for machines active the CP/M operating arrangement (the later, about absolutely accordant and added capable, Zilog Z80 processor would capitalize on this, with Z80 & CP/M acceptable the ascendant CPU & OS aggregate of the aeon about 1976 to 1983 abundant as did the x86 & MS-DOS for the PC a decade later). Even in 1979 afterwards accession of the Z80 and 8085 processors, 5 manufacturers of the 8080 were affairs an estimated 500,000 units per ages at a amount about $3 to $4 per unit.3 The aboriginal single-board microcomputers, such as MYCRO-1 and the dyna-micro were based on the Intel 8080. One of the aboriginal uses of the 8080 was fabricated in the backward 1970s by Cubic-Western Abstracts of San Diego, CA in its Automatic Fare Collection Systems custom advised for accumulation alteration systems such as BART and others about the world. An aboriginal automatic use of the 8080 was as the "brain" of the DatagraphiX Auto-COM (Computer Output Microfiche) band of articles which took ample amounts of user abstracts from reel-to-reel band and beheld it assimilate microfiche. The Auto-COM instruments aswell included an absolute automatic blur cutting, processing, washing, and dehydration sub-system – absolutely a feat, both again and in the 21st century, to all be able auspiciously with alone an 8-bit chip active at a alarm acceleration of beneath than 1 MHz with a 64 KB anamnesis limit. In addition, several aboriginal arcade video abecedarian were congenital about the 8080 microprocessor. Space Invaders was conceivably the a lot of accepted such title.

Shortly afterwards the barrage of the 8080, the Motorola 6800 aggressive architecture was introduced, and afterwards that, the MOS Technology 6502 aberration of the 6800. Zilog alien the Z80, which had a accordant machine-language apprenticeship set and initially acclimated the aforementioned accumulation accent as the 8080, but for acknowledged reasons, Zilog developed a syntactically-different (but cipher compatible) another accumulation accent for the Z80. At Intel, the 8080 was followed by the accordant and electrically added affected 8085, and afterwards by the accumulation accent accordant 16-bit 8086 and again the 8/16-bit 8088, which was called by IBM for its new PC to be launched in 1981. Afterwards NEC fabricated a NEC V20 (a 8088 carbon with Intel 80186 apprenticeship set compatibility) which aswell accurate an 8080 appetite mode. This was aswell accurate by NEC's V30 (a analogously added 8086 clone). Thus, the 8080, via its ISA, fabricated a abiding appulse on computer history.

In the Soviet Union, manufacturers cloned the 8080 microprocessor's blueprint geometry and started to aftermath them beneath the name KP580ИK80 (later apparent as KP580BM80), area even the pins were placed identically. This processor was the abject of the Radio86RK (Радио 86РК in Russian), apparently the a lot of accepted abecedarian single-board computer in the Soviet Union. Radio86RK's antecedent was the Micro-80 (Микро-80 in Russian), and its almsman the Orion-128 (Орион-128 in Russian) which had a graphical display. Both were congenital on the KP580 processor. According to some sources, the Soviet analog had two undocumented instructions, specific to itself; however, these were not broadly known.

Another archetypal accordant with Intel 8080A, called MMN8080, was produced at Microelectronica Bucharest in Romania.4 There was aswell a accordant Polish CPU called MCY78805 and the Czech-made Tesla MHB 8080A.

Industry change

The 8080 aswell afflicted how computers were created. When the 8080 was introduced, computer systems were usually created by computer manufacturers such as Digital Equipment Corporation, Hewlett Packard, or IBM. A architect would aftermath the absolute computer, including processor, terminals, and arrangement software such as compilers and operating system. The 8080 was in fact advised for just about any appliance except a complete computer system. Hewlett Packard developed the HP 2640 alternation of acute terminals about the 8080. The HP 2647 was a terminal which ran BASIC on the 8080. Microsoft would bazaar as its founding artefact the aboriginal accepted programming accent for the 8080, and would after access DOS for the IBM-PC.

The 8080 and 8085 gave acceleration to the 8086 which was advised as a antecedent accordant (not bifold compatible) addendum of the 8085. PCs based aloft the 8086 architectonics and its breed acquired into workstations and servers of 16, 32 and 64 bits, with avant-garde anamnesis protection, segmentation, and multiprocessing features, abashing the aberration amid baby and ample computers (the 80286 and 80386's adequate approach were important in accomplishing so). The admeasurement of chips has developed so that the admeasurement and ability of ample x86 chips is not abundant altered from top end architectonics chips, and a accepted action to aftermath a actual ample computer is to arrangement abounding x86 processors.

The basal architectonics of the 8080 and its breed has replaced abounding proprietary midrange and mainframe computers, and withstood challenges of technologies such as RISC. A lot of computer manufacturers accept alone bearing their own processors beneath the accomplished achievement points. Though x86 may not be the a lot of elegant, or apparently a lot of able design, the arduous bazaar force of so abounding dollars traveling into adorning a architectonics has fabricated the x86 ancestors today, and will abide for some time, the ascendant processor architecture, even bypassing Intel's attempts to alter it with adverse architectures such as the iAPX 432 and Itanium.