configuration information for booting the system. The configure mode brings up the maintenance menu for setting new configuration parameter values. The third mode requires a floppy disk to support a recovery procedure to acquire the BIOS configuration values.
3.4 Memory
The memory system of a personal computer stores the data upon which the processor operates. We would like a memory system to be fast, cheap and large, but available components can simultaneously deliver only two (any two) of the three. Modern memory systems use a hierarchy of components implemented with different technologies that together, under favorable conditions, achieve all three. When purchasing a computer system one must select the size and type of memory to be used. This section provides some background to help with that choice.
3.4.1 Memory Capacity
Along with processor speed, memory capacity has grown at a phenomenal rate, quadrupling in size approximately every three years. Integrated circuits of 64 Mbits are in use with memory modules using 256Mbit parts becoming cost effective in the near future. Prices for Random Access Memory (RAM) have also continued to decline and now cost about one dollar per MByte; a little more for higher speed/capacity SDRAMs, a little less for older and smaller DRAM. A general principle is that faster processors require more memory. With increasingly sophisticated and demanding operating systems, user interfaces, and advanced applications such as multimedia there is demand for ever increasing memory capacity. As a result of both demand and availability, the size of memory in Beowulf-class systems has progressively expanded. Today, a typical Beowulf requires at least 128MBytes of main memory and this can be expected to grow to 1 GByte within the next two to three years.
3.4.2 Memory Speed
In addition to the capacity of memory, speed of the memory can have a significant impact on the overall behavior and performance of a Beowulf node. Speed may be judged by the latency of memory access time and the throughput of data provided per unit time. While capacities have steadily increased, access times have progressed only slowly. However, new modes of interfacing memory technology to the processor managed system bus has significantly increased overall throughput of
