Server Data Bus Structures
This chapter discusses the relationship between the processor speeds and the bus speeds. It describes nonstandard structures such as the crowbars used in parallel processing operations. In modern systems while memory busses are tightly incorporated into the system design and are related to the processor in use, data busses used for peripherals are much more flexible and the current peripheral component interconnect bus is defined as processor-independent. In practice, real-world throughputs are somewhat less, about two thirds maximum for well organized and balanced systems, one half or less for poorly assembled systems such as a Pentium platform with a 16-bit ISA video card and complex graphical displays. The busses used by the IBM personal computer (PC) are an excellent starting point for understanding the evolution of bus structures. The first was the 8-bit PC-Bus introduced with the IBM PC, which runs at the same 4.77 MHz as the 8088-based PC.