Pre-Introduction
Last Edit September 24, 1996; May 1, 1999; July 9, 2001
Each of the last six decades has seen a new technology come forward
as the leading edge for that era. Table 1 provides a summary of
this evolution by decade and integration level.
Table 1 - Integrated Circuit Evolution
| Approx. Date |
Size |
Description |
| 1950s |
gate level
discrete |
A few transistors and
other components combined to form an AND, OR or NOR gates |
| mid 1960s |
SSI
Small Scale
Integration |
4 or more gates (about
2-10 gates); NAND, NOR, OR, AND, EXOR, NOT or INVERT; where
a few gates were lumped together as a means of improving the
design and the design process |
| early 1970s |
MSI
Medium Scale
Integration |
20-100 gates up to 200
gates; registers, decoders, multiplexors, counters, adders,
comparators, etc.
when more gates were packed together in a single chip for the
same reasons. MSI allows more modular designs, speeding the
design process when the blocks can be applied |
| late 1970s |
LSI
Large Scale
Integration |
200-1000+ (several hundred
gates). In the late 1970s arithmetic logic units (ALUs) with
on-board registers, microprogrammable sequencers and interrupt
controllers in a bit-slice format became available. Memory chips
(ROM, PROM, RAM) in increasing sizes became readily available.
LSI culminated in the one-chip microprocessors. |
| 1980s |
VLSI , VHLSI
Very Large Scale
Integration
(Very High-Speed
Large Scale
Integration) |
700 gates and up or 20,000
gates and higher; CPUs (central processor unit), complex functions;
where larger functional blocks and their related circuitry could
be brought together in lower power, faster chips. LSI and VLSI
further increase the modular block size, reducing design time,
space, and power considerations and increasing reliability as
connections are moved inside the components. Many LSI and VLSI
blocks are designed by their manufacturers and referred to as
fixed-instruction-set (FIS) modules. |
| 1980s |
ASIC |
up to 30,000 gates; multiple
functions |
| early 1990s |
ASIC |
up to 100,000 gates and
increasing with speeds at 1.4GHz and higher |
| 1980-1990s |
ASSP |
application specific
standard product |
| 1990s |
EPAC |
Electrically Programmable
Analog Circuit; The development of analog circuit arrays |
| 1990s |
DSM |
DSM and VDSM, Deep Submicron with chips approaching
1 million gates |
| late 1990s |
Standard Cell |
Standard cell designs
meet or beat ASICs in die size and speed of design thanks to
the evolution of design tools |
| 1990s |
capture |
Design methodology went
from schematic capture to netlist driven (Verilog, VHDL) and
designs became synthesized |
Each technology change has led to a period where those designers
who are state-of-the-art orientated, those who readily delve into
new developments, accept and begin to use the newest devices in
designs. For successful technologies, this is followed by the intense
application and development phase where the high demand for engineers
who can design with the devices typically exceeds the supply of
those engineers.
Bit-Slice Design (LSI)
For any given design, if the architecture of the fixed LSI and
VLSI blocks suit the application then the design time is considerably
shortened. When a one-chip microprocessor is not quite suitable,
microprogrammable architectures can often provide sufficient customization.
Microprogrammable architectures, such as bit-slice, allow a closer
control over the architecture but not total control. The basic building
blocks are still designed by the chip manufacturer for generic applications.
Bit-slice architectures include interruptible sequencers and 32-bit
ALUs.
The customization of the bit-slice modules to an application is
done through customer-designed module interconnection, the implemented
commands and their sequences. The commands or instruction set is
called the micro-program for the design.
ASIC (VLSI, VHLSI)
The 1980s saw the acceptance of ASICs ( application specific integrated
circuits), VLSI devices large enough to allow designers to implement
architectures that were suited to solving the design problem rather
than forcing one architecture to solve everything. It was the natural
extension to the bit-slice architectures, where some control of
architecture was possible through microprogramming but where the
basic building blocks were fixed designs.
Not far behind the ASIC and ASIC developments, multimedia and design
integration saw a need to incorporate analog functions into digital
systems. For years the trend had been away from analog design as
a chosen career and now there was a shortage of design engineers.
First came massive re-training of internal staff as companies struggled
to cope. Then came the creation of Electrically Programmable Analog
Circuit (EPAC) and related devices.
Application-specific solutions also includes the standard product
mix where the market for a device is so large that products are developed
specific to a mass application. PCI controllers is an example where
one interface controller is targeted to handle the interface for
many devices and device types, the control problem tailored to the
device via programming.
The application-specific customization of the design solution allows
the designer to have the creative power of a gate-level breadboard
design while keeping the production advantages of VLSI.
Introduction
Once upon a time....
Over the years, there has been an evolution of the universal building
blocks used by logic circuit designers. In the mid-1960s, there
were SSI gates; NAND, NOR, EXOR, and NOT or INVERT. In the early
1970s, MSI blocks, registers, decoders, multiplexors, and other
blocks made their appearances. In the late 1970s, ALUs (arithmetic
logic units) with on-board scratchpad registers, interrupt controllers,
microprogram sequencers, ROMs/PROMs, and other LSI devices up to
and including a complete one-chip microprocessor (control, ALU and
registers) became readily available. (And from this the PC was born.)
SSI (small scale integration) is defined here to include chips
containing approximately 2-10 gates. MSI (medium scale integration)
is used for chips containing 20-100 gates. LSI (large scale integration)
ships contain 200-1000 gates, with the upper limit continually extending
as VLSI (very large scale integration) became a reality. In the
mid-1980s, ASIC (application-specific integrated circuits) ranged
from 1000 gates to 20,000 gates (bipolar technology) or 200,000
(CMOS technology).
The AmZ8000 (Zilog) CPU contained 17.5K gates, the M68000 (Motorola)
claimed to have 68,000 transistors. This, of course, pales against
the 1999 chip sizes of 750,000 to 8 million gates (DSM (deep-submicron)
CMOS technology), but it is where it all began.
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