Craig R. Frink

A virtual cache-based workstation architecture

The virtual cache-based architecture of the Apollo DN4000 workstation is presented. The architecture is discussed in detail, including the main factors that influenced its final design. The influences of the operating system on the cache architecture are discussed, as well as the subsequent influences of the cache on the operating system to maintain cache coherency. It is shown how the method of assessing objects in Apollos system has led to a write-allocate cache update policy to solve the virtual address synonym problem. It is also shown how maintaining cache coherency requires special consideration by the operating system during virtual-to-physical address mapping changes, context switches, modification of data without using virtual addresses (e.g. DMA), and processor modification of page-table used bits. The primary design goal of the DN4000 was to double the CPU performance of the existing Apollo DN3000. Performance measurements indicate that use of a virtually tagged cache and a virtual write buffer lead to achievement of this goal.<<ETX>>

Low cost design for a PA-RISC color workstation

The authors present the processor, memory, graphics, multimedia, and built-in I/O design of the HP 9000 Model 710 workstation. Emphasized are the key factors considered in developing a balanced, low-cost, color workstation. Of particular interest is the use of a buffered interconnect, which enables the CPU and memory design to achieve high-performance levels within entry-level desktop constraints. The Model 710 implements a low-cost graphics architecture that delivers leading X Window performance. The graphics design of the Model 710 is reviewed, emphasizing how each part contributes to performance and limits cost. The Model 710 audio design is also reviewed, highlighting key features for improving system usability and enhancing application productivity. Finally, Model 710 performance is compared with that of other desktop members of the Series 700 workstation family, illustrating how the high performance of these workstations scales to the low-cost desktop.<<ETX>>

The cache architecture of the Apollo DN4000

The authors examine the cache architecture of the Apollo DN4000 workstation, which utilizes a virtual cache to provide a cost-effective approach to high-performance computing. Of particular interest is how the use of a virtually tagged, write-through cache made it possible to use a low-cost, off-the-shelf MMU (memory-management unit) and resulted in inclusion of a virtual write buffer. This architecture enables the processor to execute zero wait-state memory reads and writes. It is shown how the way that objects are accessed in Apollos system led to a write-allocate cache update policy to solve the virtual address synonym problem.<<ETX>>