The Enhanced Parallel Port (EPP) is a type of parallel port that allows for faster data transfer rates and bidirectional communication. This technology was developed as an extension of the original parallel port design, which was used primarily to connect printers to computers.
What is EPP (Enhanced Parallel Port): Table of Contents
The Enhanced Parallel Port (EPP) is a high-speed data transfer interface that was developed to extend the capabilities of the traditional parallel port. Unlike its predecessor, which was used primarily to connect printers to computers, the EPP was designed with versatility in mind. It could support several devices and allowed for bidirectional data communication, thus enabling not only the sending but also the receiving of data. Offering a data transfer rate of up to 2 megabytes per second, the EPP marked a significant advance over the original parallel port, which could transfer data at a rate of only about 150 kilobytes per second.
Importance and Relevance of EPP in the History of Computing
The development and implementation of the EPP were significant milestones in the history of computing. At a time when computers were becoming increasingly powerful and data-intensive, the EPP emerged as a much-needed solution to the problem of slow and unidirectional data transfer. It played a pivotal role in enabling the connection of a wider range of peripheral devices to computers, including hard disks, CD-ROM drives, and tape backup units, thereby enhancing the functionality and versatility of computing systems.
Moreover, the EPP set the stage for the development of more advanced data transfer interfaces. Its emphasis on high-speed, bidirectional communication and the ability to support multiple devices influenced subsequent technologies, most notably the Universal Serial Bus (USB), which has since become the standard for connecting peripheral devices to computers.
What are Parallel Ports
Parallel ports are a type of interface found on computers that allow the connection of peripheral devices. The term “parallel” refers to the way data is transferred; multiple bits of data are sent simultaneously along parallel lines, hence the name. This is contrasted with serial ports, where data is sent one bit at a time in a series.
Originally, the primary purpose of parallel ports was to connect printers to computers, hence its alternative name as a “printer port”. However, as technology evolved, it was adapted to connect other devices such as scanners and disk drives.
Parallel ports work by transmitting multiple bits of data at once through a series of data lines or wires. Each line carries one bit at a time, and with multiple lines working in unison, a byte (or more) can be transmitted simultaneously.
The parallel port uses a 25-pin connector, with several pins dedicated to data transfer, others used for control and status reporting, and the rest are grounded. When data is sent from the computer to the peripheral device, it is divided into bytes (8 bits). These bytes are then sent simultaneously down the data lines to the device, where they are reassembled in the correct order.
History of Parallel Ports
The first parallel port, known as the Centronics port, was developed by the company of the same name in the early 1970s. Centronics was originally a manufacturer of printers, and the port was designed to connect their printers to computers.
The Centronics port was unidirectional, meaning it could only send data from the computer to the peripheral device. It used a 36-pin connector and was capable of transmitting data at a speed of approximately 150 kilobytes per second.
The parallel port underwent several iterations to improve its functionality and performance. The IEEE 1284 standard, introduced in the 1990s, defined five modes of operation for parallel ports, including the original unidirectional mode and several bidirectional modes. These modes included the Enhanced Parallel Port (EPP) and the Extended Capabilities Port (ECP), which allowed for faster data transfer rates and bidirectional communication.
The EPP, in particular, emerged as a solution to the limitations of the Centronics port. It offered higher data transfer rates and could support multiple devices through daisy-chaining. Moreover, the bidirectional capability of the EPP made it possible for computers to not only send data to peripheral devices but also receive data from them. This marked a significant evolution in the functionality and versatility of the parallel port.
Development of the Enhanced Parallel Port (EPP)
The original Centronics-style parallel port, despite being a revolutionary development for its time, had certain limitations that became evident as computer technology progressed. Primarily, it was unidirectional, meaning it only supported data flow in one direction – from the computer to the peripheral device. This limitation hindered the potential for more complex interactions between computers and their connected devices.
Furthermore, the original parallel port had a relatively low data transfer rate, which could not exceed 150 kilobytes per second. As computers and peripheral devices became more powerful and data-intensive, this speed was insufficient to ensure efficient data transfer.
By the late 1980s, there was an increasing demand for faster, more versatile interface ports to meet the evolving needs of computing. Computers were becoming more powerful and versatile, and the peripherals were growing more complex and data-heavy. The simple, unidirectional parallel port was no longer adequate for these demanding applications. There was a clear need for an interface that could support higher data transfer rates and allow for bidirectional communication.
The Enhanced Parallel Port (EPP) was developed as a joint venture between Intel, Xircom, and Zenith Data Systems. These three industry giants pooled their expertise to create a faster, more versatile version of the traditional parallel port that could meet the increasing demands of modern computing.
The EPP was developed and introduced in the early 1990s as an extension of the IEEE 1284 standard for parallel ports. It was a timely development, coming at a moment when the growing power and complexity of both computers and peripheral devices required a more capable and versatile interface for data transfer. The EPP, with its high-speed, bidirectional communication capabilities, proved to be the right solution at the right time, marking a significant advancement in the evolution of parallel port technology.
Characteristics of the Enhanced Parallel Port
- Bidirectional Communication
One of the key characteristics that distinguishes the Enhanced Parallel Port (EPP) from its predecessor is its capability for bidirectional communication. This means that data can be sent and received simultaneously between the computer and the peripheral device. This is a significant enhancement over the unidirectional communication of the original parallel port, which could only send data from the computer to the device.
Bidirectional communication offers several benefits. Firstly, it allows for more complex and interactive operations between the computer and the device. For example, a device can send status updates or error messages back to the computer while receiving data. Secondly, it enables two-way data transfer, which can be particularly useful for devices such as scanners that need to send data to the computer.
One real-world example of bidirectional communication is the use of EPP for connecting a scanner to a computer. The scanner captures an image and sends this data back to the computer via the EPP. At the same time, the computer can send control commands to the scanner.
- High Data Transfer Rates
EPP can achieve data transfer rates of up to 2 megabytes per second, a significant increase over the original parallel port’s speed of 150 kilobytes per second. This higher speed allows for quicker and more efficient data transfer, which is crucial for high-data devices such as hard disk drives or CD-ROM drives.
Compared to the original parallel port, the EPP’s data transfer rate is over 10 times faster. This makes a noticeable difference in operations that involve large amounts of data, such as backing up data to an external hard drive or transferring large image files from a scanner.
- Daisy Chaining
Daisy chaining is a feature that allows multiple devices to be connected in a series to a single EPP. This is possible because of the bidirectional communication capability of the EPP, which allows data and control signals to be passed along the chain.
The main benefit of daisy chaining is that it enables the connection of multiple devices to a single port, saving the need for multiple ports and reducing clutter.
An example of daisy chaining with EPP could be connecting a printer, scanner, and external hard drive to a single EPP on a computer. The computer can communicate with each of these devices, and data can be passed between them via the EPP.
Comparison with Other Parallel Port Types
- Standard Parallel Port (SPP)
The Standard Parallel Port (SPP) is the original type of parallel port, also known as the Centronics port. Compared to the SPP, the EPP offers higher data transfer rates, bidirectional communication, and the capability for daisy chaining.
- Extended Capabilities Port (ECP)
The Extended Capabilities Port (ECP) is another type of parallel port that was developed around the same time as the EPP. The ECP also offers high-speed, bidirectional communication and has some additional features such as direct memory access (DMA) for faster data transfer. However, ECP is more complex and requires more advanced hardware and software support compared to EPP.
EPP in Practice
Numerous devices leveraged the capabilities of the Enhanced Parallel Port during its peak usage period. These devices include, but are not limited to:
- Printers: One of the most common uses of the EPP was to connect printers to computers, allowing for faster and more efficient printing processes compared to the original parallel port.
- Scanners: The bidirectional communication capability of the EPP was particularly useful for scanners, which needed to send data back to the computer.
- External Hard Drives and CD-ROM Drives: The high data transfer rate of the EPP made it an ideal choice for connecting high-data devices such as external hard drives and CD-ROM drives.
- Zip Drives: During the 1990s, Zip drives were a popular means of portable storage, and many of these drives used the EPP for connection to computers.
Real-World Use Cases and Applications
- Data Backup: The high data transfer rate of the EPP was particularly useful for data backup operations, which often involved transferring large amounts of data to an external hard drive.
- Image Scanning: Scanners could leverage the bidirectional communication of the EPP to send scanned image data back to the computer while receiving control commands.
- Printing: Printers connected via an EPP could print faster and more efficiently, and could also send status updates or error messages back to the computer.
Strengths and Weaknesses of Using EPP
| Strengths | Weaknesses |
|---|---|
| High-speed data transfer | Hardware compatibility issues |
| Bidirectional communication | Became obsolete with the advent of USB |
| Daisy chaining | Designed for short-distance communication |
The Decline of the EPP
The Universal Serial Bus (USB) was introduced in the mid-1990s, around the same time as the Enhanced Parallel Port. Like the EPP, the USB was designed for high-speed, bidirectional communication between computers and peripheral devices. However, USB offered several advantages over the EPP that eventually led to its widespread adoption.
Unlike the EPP, which used parallel data transmission, the USB used serial data transmission. While parallel transmission sends multiple bits of data simultaneously along multiple lines, serial transmission sends data one bit at a time along a single line. This might sound like a disadvantage, but in practice, it allowed for higher data transfer rates because it avoided the problem of signal timing skew that can occur with parallel transmission.
Furthermore, the USB was designed to be “hot-swappable”, meaning devices could be connected or disconnected without needing to restart the computer. This was not possible with the EPP.
Advantages of USB over EPP
USB offered several key advantages over the EPP, including:
- Faster Data Transfer Rates: USB initially offered data transfer rates comparable to EPP, but subsequent versions of USB have far exceeded EPP’s speed capabilities.
- Hot-Swappable: The ability to connect or disconnect devices without restarting the computer was a significant advantage of USB.
- Power Supply: USB cables can supply power to connected devices, eliminating the need for separate power cables for some devices.
- Greater Compatibility and Standardization: USB quickly became the standard for connecting peripheral devices, with broad support from hardware and software manufacturers.
The Shift from EPP to USB
As USB became more popular and its advantages became more apparent, the computing industry gradually shifted away from the EPP and other types of parallel ports. Manufacturers began to include USB ports in their computers and peripheral devices, and developers started to design software and drivers with USB in mind. Over time, the EPP became less and less common, and by the early 2000s, it was largely obsolete.
Current Status of EPP in Modern Computing
Today, the EPP is rarely found in modern computing systems. USB, and more recently USB-C, have become the standard interfaces for connecting peripheral devices to computers. They offer higher data transfer rates, greater ease of use, and broader compatibility than the EPP.
However, the EPP’s legacy lives on. It played a crucial role in the transition from the early days of computing, when printers were the primary peripheral devices, to the modern era, with a wide range of complex, data-intensive devices. And it paved the way for the development of USB and other advanced interfaces. While the EPP itself is largely a thing of the past, its impact on the field of computing continues to be felt.