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A port expander is computer hardware that allows more than one device to connect to a single port on a computer. The Commodore VIC-20 used a port expander to allow more than one cartridge to be connected to the single ROM cartridge port.
A port expander can be any device to which one existing or onboard port becomes two or more. E.G. a KVM switch or a USB hub. One advantage is the ability to allow more devices of a particular port type to be utilized at the same time, a major down side is that for example, a 3Gbit/s port would have a hub or expander installed and now be able to accommodate 6 devices, but at a max of 3Gbit/s throughput bandwidth divided by said 6 devices, or however many are plugged in and being used. A port expander is a device that allows one port on a computer system to connect to multiple devices. There are two basic forms of port expander: internal and external. An internal expander has a connection inside the computer, typically on the motherboard, and the only part the user sees is the expansion plate containing multiple ports. An external device plugs into the existing port and then has multiple places to connect. When not part of a computer system, these devices are commonly known as splitters.
In the non-computer world, splitters are very common. Extension cords and power strips are in nearly every modern home. Both of these devices will split a single outlet to multiple devices. Cable splitters are also in many homes, allowing a single coaxial cable to provide cable television to multiple sets. Some systems may even use an A/B box, a device that connects multiple sets of devices to the same system, but switches between them by flipping between the A or B mode.
These devices are all doing the same basic job that a port expander does. The expander will connect to a single spot, but have multiple connections for devices. They go by several names, such as switch, hub or splitter, but they all do the same thing. Expanders are made for nearly every type of port, but the most common household versions are for universal serial bus (USB) and Ethernet ports.
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