UPGRADING REPAIRING PCs

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Chapter 7—Parallel Ports, Printers, Scanners, and Drives
Parallel Port Performance
As printers have gotten faster and more devices are attached to parallel
ports, the need for increasing parallel port speed has become
more and more apparent. High-speed laser and inkjet printers, tape
backup drives, CD-RW drives, and parallel port-to-SCSI converters
can all benefit from using the fastest parallel port modes available
on your system.
Use the following tables to help determine whether your parallel
ports are set to the fastest standard supported by your printers or
other parallel port devices. On most computers, you adjust these
parallel port settings through the CMOS/BIOS configuration
screens. If the port is on an expansion card, you might use jumper
blocks or a setup program to change the settings.
Table 7.1 summarizes the various types of parallel ports, their input
and output modes, speed, and hardware settings.
Table 7.1 Parallel Port Types as Defined by IEEE-1284
Parallel Port Input/
Type Input Mode Output Mode Output Speed Comments
SPP Nibble Compatible Input: 50KB/ 4-bit input,
(Standard (4 bits) second 8-bit output
Parallel Output:
Port) 150KB/second
Compatible Input/Output Bidirectional Byte
(8 bits) 8-bit I/O:
150KB/second
EPP EPP EPP Input/Output: 8-bit I/O,
(Enhanced 500KB– uses IRQ
Parallel Port) 2MB/sec
ECP (Enhanced ECP ECP Input/Output: 8-bit I/O,
Capabilities 500KB– uses IRQ
Port) 2MB/sec and DMA
EPP Versus ECP Modes
Both EPP and ECP ports are part of the IEEE-1284 bidirectional parallel
port standard, but they are not identical. Use the following
table to understand how they differ, and consult your parallel port
device manuals to see which mode is best for your system.
Port Type IRQ Usage DMA Usage Designed For Notes
EPP Yes No Tape drives, Version 1.7 predates
(Table 7.2) CD-ROM, LAN IEEE-1284 standard;
adapters IEEE-1284 version
often called EPP 1.9