40 years ago we entered the megabit memory era with IBM’s DRAM breakthrough — a major leap beyond the 64 kilobit chips common at the time
IBM framed the announcement as American tech fighting back against Japan’s increasing domination of the memory market.
40 years ago today IBM was in the news for becoming the first computer company to make use of 1-megabit memory chips. Thus, the megabit memory era began with an American company and its Vermont fab leading the way, pushing back stubbornly against the seemingly unstoppable Japanese takeover of the memory market.
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IBM’s 3090 (Sierra series) mainframe computers were the first to adopt this new high-density memory. However, the New York Times reported the occasion as “a rare, if fleeting, moment of glory,” as it thought the Japanese semiconductor industry would inexorably rise beyond its already impressive 75% market share.
The NYT’s take contrasted with IBM’s triumphant tone. “This is a signal of our semiconductor technology leadership,” said IBM SVP, Jack D. Kuehler, at the time. He went on to emphasize how these DRAM chips were built in the USA. Some of the newspaper’s cynicism came from the fact that it already knew the likes of Fujitsu, Hitachi, Mitsubishi, NEC, and Toshiba were busy sampling their own 1-megabit DRAM chips. Once they were satisfied and moved them to mass production, it was expected the Far East tiger economy would roar back to pole position.
If we turn the clock back to 1986, most computing devices in use might have packed memory chips of the 64 kilobit variety. The state-of-the-art Japanese memory tech at the time was churning out 256 kilobit memory chips. In that context IBM’s 1-megabit chips, fabricated on a 1.2 micron process, were very impressive, bringing a leap in both density and efficiency.
The arrival and establishment of 1-megabit memory chips would enable memory makers to produce 30-pin SIMMs with 1MB RAM capacity, using eight to nine chips in a single-side configuration. Such SIMMs will be very familiar to users of home and personal computers from the mid-1980s to the mid-1990s. Additionally, you would be able to use the same SIMMs in printers, on sound cards, and even graphics cards like the Tseng ET3000 / ET4000, Trident TVGA 8800 / 8900, and Cirrus Logic GD542x series.
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Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.
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dakra More interesting than the 8 or 9 chip SIMMs were the 6 chip 512KB SIPs made from defective chips. Fab yield was good, but there were plenty of 1Mb chips that had defects. Usually the defects concentrated entirely in only one of a chip's four 256Kb quadrants.Reply
IBM selectively wired together the 18 good 256 Kb quadrants on 6 of those chips, to make an 18 bit-wide, 512KB w/parity SIP. These went into some PS/2's, particularly the 8086 versions of the PS/2 Model 30.
These 3/4-good chips did not get into mainframes, but they were not discarded, either. The discard percent dropped into the single digits.