Eberle, J. J. Development and Analysis of a Workstation Computer (1987)

« Abstract

The workstation Ceres is a stand-alone computer for a single user. The design is an example of a simple system architecture reflected by a careful implementation with minimal costs. Ceres is based on the 32-bit microprocessor NS32032, which is oriented to the use of high-level and modular languages. A key feature is the high-resolution bitmapped graphics display which is attractive for applications such as program development or document processing. The arbitrated memory bus and the modular system organization are open to future hardware extensions.

This thesis documents the hardware development of the workstation Ceres. The design objectives of the raster graphics interface and of the bus structure are discussed in detail. Finally, processor-memory communication of two prototype versions is analysed, which differ only in the width of their data paths to memory.

The raster graphics interface of Ceres contains an integral frame buffer memory, which is directly addressable by the CPU. The frame buffer is based on video RAM technology which ideally meets the high video bandwidth requirements of the 1024 x 800 non-interlaced display. An inexpensive and flexible solution is retained by dispensing with dedicated hardware support for image manipulation.

The backbone of the Ceres computer is the memory bus, which is shared by multiple master devices. The bus is controlled by a centralized arbiter. Short response times are ensured in that the shared memory is re-allocated for every memory cycle according to fixed priorities. A default assignment strategy prevents the processor from being significantly slowed by arbitration delays.

The analysis of processor-memory communication is motivated by the observed small benefit in performance gained by replacing the NS32016 CPU with the NS32032 CPU and thus doubling the memory bus bandwidth. [Measurements] show that the bus capacity of the NS32032-based Ceres is only used to a small degree. Therefore, the additional costs can hardly be justified. This contrasts with the frequently heard claims of the superiority of 32-bit computers. »

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