Technology scaling has yielded a wealth of transistor resources and largely commensurate improvements in chip performance. These benefits, however, have come with an ever increasing price tag, due to rising design, engineering, validation, and ASIC initiation costs. When designing a product, engineers must choose between two less than ideal options. Either they must face the high fixed costs of ASIC production, and hope to amortize it over a large volume of parts, or they must choose an FPGA with low fixed costs, but high unit part cost. The trade-offs are not just financial. ASICs provide significant speed (3-4x) and power (up to 12x) savings , compared to FPGAs, and certain applications, such as cell-phones, will simply require an ASIC for these technical advantages. However, FPGAs bring in-field reprogrammability, which is useful for accomodating changing standards. This drives the need for a manufacturing technology that provides the key advantages of FPGAs coupled with the key advantages of ASICs.
Researchers at the University of Michigan have invented a novel fabrication tech-nique called “brick and mortar'‘, in which chips are made from small, pre-fabricated ASIC bricks, assembled according to designer specifications and bonded to an I/O cap. At the heart of this manufacturing technique are two architectural components: bricks, which are mass-produced pieces of silicon containing processor cores, memory arrays, small gate arrays, DSPs, FFT engines, and other IP (intellectual property) blocks; and mortar, an I/O cap, that is a mass-produced silicon substrate. Engineers design products with the brick and mortar process by putting together pre-produced bricks of IP into an application-specific layout. This arrangement of bricks is then bonded to the I/O cap, which interconnects them. The goal of brick and mortar assembly is to provide a low-overhead method to produce custom chips, yet with performance that tracks more closely an ASIC than an FPGA.
Applications and Advantages
- Chip design and manufacturing, digital circuits
- Low overhead costs for producing custom chips
- High performance
- Can be mass-produced, thus increasing manufacturing rate and lowering production costs