Professor of Computer Science
Ph.D., Brandeis University
Professor Gottlieb directs the Ultracomputer group. This group began in 1979 with simulation and theoretical studies. Hardware (Ultra I) appeared in 1982-83 and by 1985 several Ultra II systems were in production use. Each included eight, 10-MHz 68010 processors (like the SUN 2, a contemporary) each with a cache connected via a bus to 16MB of shared memory.
They designed and implemented a highly parallel Unix, which, like the Ultra II hardware, proved quite reliable. In the second half of the decade, each system averaged about one (hardware or software) crash per month, including the stress test of having several parallel programming courses use it as their class computer.
The Ultracomputer group modified C and Fortran compilers to support parallel programming and this group became the center for GCC (GNU C compiler) development. One student from the group developed a parallel lisp including a parallel garbage collector.
The Ultracomputer group advocates combining simultaneous references directed at the same memory location. Ultra III achieves this objective, using custom VLSI chips designed by this group and fabricated by MOSIS. Ultra III contains 16 AMD-29050 processors with caches, and 256MB of shared memory connected using their own combining, buffered crossbar switches.
Many parallel applications have been run on their system, most developed by researchers outside this group.