ShareCG: ASICs ... the Book

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1.3 Case Study

Sun Microsystems released the SPARCstation 1 in April 1989. It is now an old design but a very important example because it was one of the first workstations to make extensive use of ASICs to achieve the following:

  • Better performance at lower cost
  • Compact size, reduced power, and quiet operation
  • Reduced number of parts, easier assembly, and improved reliability

The SPARCstation 1 contains about 50 ICs on the system motherboard—excluding the DRAM used for the system memory (standard parts). The SPARCstation 1 designers partitioned the system into the nine ASlCs shown in Table 1.1 and wrote specifications for each ASIC—this took about three months 1 . LSI Logic and Fujitsu designed the SPARC integer unit (IU) and floating-point unit ( FPU ) to these specifications. The clock ASIC is a fairly straightforward design and, of the six remaining ASICs, the video controller/data buffer, the RAM controller, and the direct memory access ( DMA ) controller are defined by the 32-bit system bus ( SBus ) and the other ASICs that they connect to. The rest of the system is partitioned into three more ASICs: the cache controller , memory-management unit (MMU), and the data buffer. These three ASICs, with the IU and FPU, have the most critical timing paths and determine the system partitioning. The design of ASICs 3–8 in Table 1.1 took five Sun engineers six months after the specifications were complete. During the design process, the Sun engineers simulated the entire SPARCstation 1—including execution of the Sun operating system (SunOS).

TABLE 1.1 The ASICs in the Sun Microsystems SPARCstation 1.

SPARCstation 1 ASIC

Gates (k-gates)


SPARC integer unit (IU)




SPARC floating-point unit (FPU)




Cache controller




Memory-management unit (MMU)




Data buffer




Direct memory access (DMA) controller




Video controller/data buffer




RAM controller




Clock generator



Table 1.2 shows the software tools used to design the SPARCstation 1, many of which are now obsolete. The important point to notice, though, is that there is a lot more to microelectronic system design than designing the ASICs—less than one-third of the tools listed in Table 1.2 were ASIC design tools.

TABLE 1.2 The CAD tools used in the design of the Sun Microsystems SPARCstation 1.

Design level


Tool 2

ASIC design

ASIC physical design

LSI Logic


ASIC logic synthesis

Internal tools and UC Berkeley tools


ASIC simulation

LSI Logic

Board design

Schematic capture

Valid Logic


PCB layout

Valid Logic Allegro


Timing verification

Quad Design Motive and internal tools

Mechanical design

Case and enclosure



Thermal analysis

Pacific Numerix


Structural analysis







Interleaf and FrameMaker

The SPARCstation 1 cost about $9000 in 1989 or, since it has an execution rate of approximately 12 million instructions per second (MIPS), $750/MIPS. Using ASIC technology reduces the motherboard to about the size of a piece of paper—8.5 inches by 11 inches—with a power consumption of about 12 W. The SPARCstation 1 “pizza box” is 16 inches across and 3 inches high—smaller than a typical IBM-compatible personal computer in 1989. This speed, power, and size performance is (there are still SPARCstation 1s in use) made possible by using ASICs. We shall return to the SPARCstation 1, to look more closely at the partitioning step, in Section  15.3, “System Partitioning.”

1. Some information in Section 1.3 and Section 15.3 is from the SPARCstation 10 Architecture Guide—May 1992, p. 2 and pp. 27–28 and from two publicity brochures (known as “sparkle sheets”). The first is “Concept to System: How Sun Microsystems Created SPARCstation 1 Using LSI Logic's ASIC System Technology,” A. Bechtolsheim, T. Westberg, M. Insley, and J. Ludemann of Sun Microsystems; J-H. Huang and D. Boyle of LSI Logic. This is an LSI Logic publication. The second paper is “SPARCstation 1: Beyond the 3M Horizon,” A. Bechtolsheim and E. Frank, a Sun Microsystems publication. I did not include these as references since they are impossible to obtain now, but I would like to give credit to Andy Bechtolsheim and the Sun Microsystems and LSI Logic engineers.

2. Names are trademarks of their respective companies.

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