History of Micro-Computers - The MESSUI Place

MICRO PROCESSOR EVOLUTIONwho was happy to talk about his newprocessors.I sat down on the couch and lookedat the two manuals. They were writtenin English and they made sense!MOS was also showing one more innovationin the suite that night—thefirst multifunction peripheral chips.The company had put RAM, ROM,timer, and I/O on one chip. One versionwas called the TIM (terminalinterfacemonitor) chip and containeda complete monitor for talkingto a serial terminal. The other was theKIM (keyboard-input monitor) chip,and it was designed into a microcomputerboard that had a keyboard, centralprocessor, display, ROM, RAM,and parallel I/O, and sold for $245. Itwas a complete system. No othermicroprocessor vendor had doneanything like this before. It wasimpressive.I went home that evening clutchingmy $25 6502 microprocessor and twomanuals. At the time I didn't realizeI would spend another $300 to makea working system, not counting theASR-3 3 Teletype I used as a terminal.That first day of WESCON, Intel andMotorola lowered the price on theirchips to $69.95. The revolution wasin full swing. The industry would neverbe the same.The 6501 was short-lived. Motorolasued MOS Technology charging thatChuck Peddle had stolen the technologyfrom Motorola and that the6501 infringed because it was plugcompatible.MOS 'Technology agreedto drop the 6501.However, the many computers thatwere developed around the 6502 arenow legend: MOS Technology's ownKIM-1, the Apple I and II, the Atarimodels, and the Commodore PETand VIC-20, among others. Actually,the future of the 6502 was still questionablewhen fledgling Apple ComputerInc. produced the Apple I. SteveWozniak put in a jumper connectionthat could be changed to allow the6800 to be used instead of the 6502.ENTER THE Z80Sometime in late 1975 or early 1976,Federico Faggin left Intel and formed264 JUST COMPUTERS • DECEMBER 1985his own company, Zilog Inc. He tookMasatoshi Shima with him. Their goalwas to build a super 8080.In 1976, Zilog announced the Z80,a significantly enhanced 8080 that ranalmost all of the programs written forthe 8080. The company claimed itwould have parts that ran at 4 MHz,twice as fast as the 8080. In additionit had many more powerful instructions—atotal of 176. It sounded toogood to be true; the Z80 was treatedwith the same skepticism as the 6502had been.But the Z80 turned out to be real,and there actually were some 4-MHzparts available. The early ones said"Engineering Sample" on them andwere manufactured in Dallas, not inSilicon Valley. Mostek, a Z80 secondsource, was actually building the chipsfor Zilog. Nobody minded becauseeverybody wanted one for their owncomputer.Several Z80 cards for the S-100 buswere on the market shortly after thechip became available, and everybodyhad to have one. But even though theZ80 was a much more powerful chipthan the 8080 in terms of its instructionset, very few people were writingsoftware to take advantage of theZ80's extra instructions. The reasonwas simple: The majority of themachines installed at that time were8080-based, and if you wrote codethat only ran on a Z80, your marketwould be 'considerably smaller. Thisproblem plagues the Z80 even today.However, designers stopped usingthe 8080 in new computers. The Z80was a far easier chip to use, requiringno support ICs and only a singlevoltagepower supply. And it wasmuch faster, even if you didn't use theextra instructions.The Z80 introduced one other newconcept to microcomputer chips:built-in support for refreshingdynamic RAMs. Dynamic RAMs havealways cost about four times less perbit than their static counterparts, andthat made th(pm very attractive to use.However. because you have to refreshthem (or else they forget their data),they are extremely difficult to use, andearly system designers viewed themwith some distrust. The Z80 gave thedesigner 90 percent of the solutionand made it possible to build systemsthat were significantly cheaper thanbefore. Computers such as RadioShack's original TRS-80, designed bySteve Leininger, took advantage ofthis fact.INTEL STRIKES BACKMeanwhile Intel had realized that the8080 needed upgrading. In 1976 Intelannounced the 8085. It had all the8080 instructions, plus a few more.But Zilog had taken Intel by surprise.The enhancements that the 8085 hadover the 8080 were nowhere near asextensive as those of the Z80. Froma purely hardware standpoint, the8085 was a much nicer chip than theZ80, but the Z80 had mass appealbecause it was faster. When introduced,the 8085 ran at 3 MHz, as opposedto the 4-MHz chip that Zilogwas already shipping. Intel had tocome up with something else—a16-bit processor seemed like theanswer.Sixteen-bit processors had beentried before. National Semiconductorhad started work on the IMP-I6 chipset as early as 1972. The companyreduced it to one chip called the Pace.and Bill Godbout Electronics announceda Pace-based computer, designedby George Morrow, in mid-1975. The unnamed system. a fullblown16-bit computer with RAM anda built-in cassette interface, was advertisedin the first issue of BYTE. Theyactually built one, but it never got tomarket. Bill Godbout said that themarket wasn't ready for a 16-bit computer,and he was probably right.After all, the Altair was only a fewmonths old itself. Neither the Pacechip nor the computer was ever a hit.Other 16-bit chips included GeneralAutomation's LSI-16, a microprocessorversion of its SPC-16 minicomputer;DEC's-LSI-11, which was manufacturedby Western Digital and includedthe .PDP-11 instruction set;Western Digital's own WD-11, whichwas only one instruction differentfrom the LS1-11; General Instrument'sCP1600; and 'Texas Instruments'