An important factor to remember in discussing present day devices is that they represent one sample point about 70%of the way through an approximate 17-year life cycle. A technology generation goes through three phases of maturity: a seven-year research period, a five-year development period, and a five-year manufacturing period. For any given generation, identifying when one period ends and another begins is difficult, and devices from different technology generations co-exist in time.
Leading-edge microprocessors being shipped today were introduced in the 1992-1993 time period. Fabrication technology minimum feature size ranges from 0.8 micrometers down to 0.6 micrometers. In 1994, processors will be introduced that exploit 0.5 micrometer technology. About a two-year lag exists between the technology roadmap year and the actual introduction of the technology in a microprocessor product. Current commercial device complexity, measured in terms of transistor count, is about 3 million transistors per chip. The Intel Pentium and the TI Super Sparc are at the high end with 3.1 million transistors, and the IBM/Motorola PowerPC 601 follows with 2.8 million.
New 1994 chip announcements already are significantly changing both
device complexity levels and architectural approaches. The TI 320C80
digital signal processing device, with five separate programmable
processors, has about 4.5 million transistors. Another example is the
26 million transistor Analog Devices 21060 chip. Its high transistor
count arises from its large amount of memory. Power dissipation for
current devices ranges from about 1 watt to 30 Watts. CMOS
dissipation is usually dominated by dynamic power (i.e., ).
Fabrication processes developed for low voltage operation provide an important edge in achieving high throughput per watt performance. For a given voltage level, power is a function of circuit design and specific operating mode rather than an intrinsic technology characteristic, and the power variation between chips can be expected to remain large.
Single-chip microprocessor packages vary from about 168 to 504 pins. Signal pin counts will grow in the near term, but will not be a universal phenomena. Some processor designs will move high pin count signal interfaces on-chip. An important issue related to pin out is the need for multiple power and ground connections. In order to reduce series inductance, high-performance devices will move rapidly to hundreds of power system connections. A long-term expectation is that the positioning of device pads will move from the perimeter of chips to over the entire surface of the die.
Clock rates are typically for high-performance computers
produced in volume, and some chips run as high as
. A new
version of the DEC Alpha chip fabricated with 0.5 micron technology is
expected to run with a
clock. It is now common for chips
to employ on-chip clocks which are much faster than the off-chip
clock. Factors of two times, three times, and four times are being
used.