As data buses are used in computers to transfer information in the memory and to extract it, the key differences regard the speed and volume of data that they can carry. There are various types of data buses functioning in microcomputers that vary by speed, bandwidth, and maximum data rate. Elahi (2018) describes such buses as ISA, EISA, MCA, VESA, and PCI as the most frequent in microcomputers.
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The oldest data bus
The ISA (industry standard architecture) bus operates at 8 MHz speed, and it is one of the oldest data buses. As it has a bandwidth of 16-bit and no plug-and-play capability, it has been superseded by AGP and PCI. The MCA created by IBM was capable of plug transferring 32-bit address lines and 16-bit data at the speed of 10 MHz. However, the bus was costly, so it was replaced by a cheaper substitute called EISA. The latter has a width of 32 bits but still can support 8-bit and 16-bit data transfers.
A new generation
The previously used types of data buses quickly became outdated. According to Zhang (2020), the development of a faster CPU facilitated the appearance of new generation buses. PCI and PCI-x (PCI Extended) buses are peripheral components interconnects that run at 33/66 MHz speed, respectively. Elahi (2018) claims that the main advantage of PCI buses is the bandwidth of up to 1 Gbps. It also offers several improvements comparing to the previous generation buses, allowing connection to routers, hubs, and networks. However, the development of hardware required higher bandwidth, and PCI was replaced by a newer version called PCI Express (PCIe).
Its main features are the point-to-point connection, the use of layer and pocket architecture, and compatibility with PCI buses. Moreover, PCIe belongs to serial buses, such as USB, SATA, or IEEE, that are currently replacing parallel buses.
Elahi, A. (2018). Computer systems: Digital design, fundamentals of computer architecture, and assembly language. Cham, Switzerland: Springer International Publishing.
Zhang, F. (2020). High-speed serial buses in embedded systems. Cham, Switzerland: Springer.