Page 106 - A Practical Guide from Design Planning to Manufacturing

Design Planning 81

TABLE 3-3 Designer Productivity
Logic block size Design productivity
(number of transistors) (transistors/engineer year)
Tiny blocks (<10 K) 36 K
Small blocks (10 K–300 K) 160 K
Large blocks (300 K–4 M) 224 K

created for a given manufacturing generation and then assembled into
many different designs. Smaller fabless companies license the use of
these libraries from manufacturers that sell their own spare manufac-
turing capacity. The recent move toward dual core processors is driven
in part by the increased productivity of duplicating entire processor cores
for more performance rather than designing ever-more complicated cores.
The size of the design team needed will be determined both by the type
of design and the designer productivity with team sizes anywhere from
less than 50 to more than 1000. The typical types of positions are shown
in Table 3-4.
The larger the design team, the more additional personnel will be
needed to manage and organize the team, growing the team size even
more. For design teams of hundreds of people, the human issues of clear
communication, responsibility, and organization become just as impor-
tant as any of the technical issues of design.
The headcount of a processor project typically grows steadily until
tapeout when the layout is first sent to be fabricated. The needed head-
count drops rapidly after this, but silicon debug and beginning of produc-
tion may still require large numbers of designers working on refinements
for as much as a year after the initial design is completed. One of the most
important challenges facing future processor designs is how to enhance pro-
ductivity to prevent ever-larger design teams even as transistors budgets
continue to grow.
The design team and manpower required for lead designs are so high
that they are relatively rare. As a result, the vast majority of processor

TABLE 3-4 Processor Design Team Jobs

Position Responsibilities
Computer architect Define instruction set and microarchitecture
Logic designer Convert microarchitecture into RTL
Circuit designer Convert RTL in transistor level implementation
Mask designer Convert circuit design into layout
Validation engineer Verify logical correctness of design at all steps
Design automation engineer Create and/or support design CAD tools