Hop on the Bus, Gus

Hop on the Bus, Gus :
Gus Buses have grown and evolved over the years in an effort to match the performance of all the other computer components. Even so, the evolution of the bus has been surprisingly slow compared to other technologies. Most computers sold today still have an Industry Standard Architecture (ISA) bus that will accept computer cards developed for the original IBM PC in the early 1980s. There have been a couple of key reasons for this bus longevity:
• There is a need for long-term compatibility with a large number of hardware manufacturers. • Before the rise of multimedia, few hardware peripherals fully utilized the speed of the bus. A typical computer has two key buses. The first one, known as the system bus or local bus, connects the microprocessor (central processing unit) and the system memory. Other buses, such as the ISA and PCI buses, connect to the system bus through a bridge, which is a part of the computer's chipset and acts as a traffic cop, integrating the data from the other buses to the system bus. As the speed of central processing units (CPUs) and RAM increased, it became more important to isolate the path between processor and memory. A replacement for the standard system bus, called Dual Independent Bus (DIB), was created. DIB replaced the single system bus with a frontside bus and a backside bus. The backside bus had one purpose: to provide a direct, fast channel between the CPU and the Level 2 cache. The frontside bus connected the system memory, via the memory controller, to the CPU, and the other buses to the CPU and system memory.The other main bus, the shared bus, is for connecting additional components to the computer. It is called a shared bus because it lets multiple devices access the same path to the CPU and system memory. These devices includes such items such as:
• Modem
• Hard drive
• Sound card
• Graphics card
• Controller card
• Scanner The original PC bus operated at 4.77 MHz (million cycles per second) and was 8 bits wide, meaning it could process 8 bits of data in each cycle. In 1982, it improved to 16 bits at 8 MHz and officially became known as ISA. This bus design is capable of passing along data at a rate of up to 16 MBps (megabytes per second), fast enough even for many of today's applications. As technology advanced and the ISA bus grew long in the tooth, other buses were developed. Key among these were Extended Industry Standard Architecture (EISA) -- which was 32 bits at 8 MHz-- and Vesa Local Bus (VL-Bus). The cool thing about VL-Bus (named after VESA, the Video Electronics Standards Association, which created the standard) is that it was 32 bits wide and operated at the speed of the local bus, which was normally the speed of the processor itself. The VL-Bus essentially tied directly into the CPU. This worked okay for a single device, or maybe even two. But connecting more than two devices to the VL-Bus introduced the possibility of interference with the performance of the CPU. Because of this, the VL-Bus was typically used only for connecting a graphics card, a component that really benefits from high-speed access to the CPU.