![]() It was targeted specifically for non-printer devices that would attach to the parallel port, particularly storage devices that needed the highest possible transfer rate. EPP allows for much more data, 500 kilobytes to 2 megabytes, to be transferred each second. This allows for full-duplex (both directions at the same time) communication.Įnhanced Parallel Port (EPP) was created by Intel, Xircom and Zenith in 1991. But pins 18 through 25, originally just used as grounds, can be used as data pins also. Using the same eight pins limits communication to half-duplex, meaning that information can only travel in one direction at a time. ![]() Many devices use the eight pins (2 through 9) originally designated for data. Bidirectional communication allows each device to receive data as well as transmit it. This mode is commonly known as Standard Parallel Port (SPP) and has completely replaced the original design. With the introduction of the PS/2 in 1987, IBM offered a new bidirectional parallel port design. Even on newer 2017 models, iMacs native SD card slots are still not using UHS-II card readers. Many of these adapters card slots do not support UHS-II or UHS-III standard yet. The original specification for parallel ports was unidirectional, meaning that data only traveled in one direction for each pin. Since Apples shift to universal USB-C ports, newer MacBook models require Type-C dongles and adapters to connect other peripherals, including micro and SD cards.
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