CPU congestion is a type of bottleneck caused by an excessively high demand on the capabilities of a processor in a given network or system.
The enhanced parallel port (EPP) is an old, but still widely used, standard input/output (I/O) interface that connects peripheral devices, such as a printer or a scanner, to a PC. The four standard parallel ports are the parallel port (PS/2), standard parallel port (SPP), EPP and extended capabilities port (ECP). The EPP is quicker than older ports and can transmit more data while allowing channel direction switching. This port is appropriate for portable hard drives, data acquisition and network adapters. The EPP is used mainly for PCs that support eight-bit bidirectional communication at Industry Standard Architecture (ISA) bus speeds. EPP introduced advanced performance with backward SPP compatibility. The EPP is about 10 times faster than the older port modes.
A parallel port was first used in 1981 to provide a physical interface between a PC and a printer. The original parallel port was called the normal port or SPP, and it soon became a de facto standard for most PCs. By 1987, the PS/2 was introduced. This port was a lot faster and had bidirectional port capabilities. The PS/2 could read data from a peripheral device to the host. The bidirectional EPP was developed in 1994 to provide a high-performance interface. This mode was implemented as part of the Institute of Electrical and Electronics Engineers (IEEE) standard. The bidirectional ECP was also introduced in 1994 by Microsoft and Hewlett Packard for use with printers and scanners. It features direct memory access (DMA), first in/first out (FIFO), data compression and channel addressing. The original standard parallel port (SPP) was unidirectional (one direction) and could transfer eight-bit data. The PS/2 parallel port introduced an eight-bit bidirectional data port that was two times faster. Both the SPP and PS/2 transferred data at a rate of 50 to 150 KBps. Each new parallel port design helped improve the performance and speed of data transfer.Both the EPP and ECP support an eight-bit bidirectional port. Usually, EPP is used for newer models of printers and scanners, whereas ECP is used for non-printer peripherals, such as network adapters or disk drives. Although EPP and ECP are quite different, there are modern products that support both EPP and ECP collectively.
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