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All-In-One Chapter 8: Expansion Bus 305 Figure 8-19 IOAPIC at work the new device will take up one of these unused IRQs. Now look at the older PIC system
in Figure 8-21note that it only shows IRQs ranging from 0 through 15.
Modern systems running Windows Vista or Windows 7 can use virtual IRQs to support devices. A quick glance at the Device Manager IRQ list in Vista shows a giant list of
IRQs, ranging from 0 to upwards of 190 (Figure 8-22). Some systems even display negative IRQs, such as –2 or –4. Once you get into a Windows Vista or Windows 7 machine,
you can pretty much forget about IRQs. The OS handles it all automatically.
Let’s look at the last serious vestige of the “bad old days” on your PC: COM and LPT
ports. COM and LPT Ports
When the PC first came out, the I/O addresses and IRQ for every device had to be
manually configured. How you did this varied from device to device: you moved jumpers, turned dials, or ran weird configuration programs. It was never easy. IBM tried to
make configuration easier by creating preset I/O address and IRQ combinations for ch08.indd 305 12/14/09 2:49:28 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 8 CompTIA A+Certification All-in-One Exam Guide 306 Figure 8-20 IRQs in an IOAPIC system Figure 8-21 IRQs in a PIC system ch08.indd 306 12/14/09 2:49:30 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 8
All-In-One Chapter 8: Expansion Bus 307 Figure 8-22 IRQs in Windows Vista the serial and parallel ports, because they were the most commonly used ports on the
original PC. These preset combinations were called COM ports for serial connections
and LPT ports for parallel ports. Table 8-1 lists the early preset combinations of I/O addresses and IRQs.
TIP The term “COM” for serial ports came from “communication,” and the
term “LPT” for parallel ports came from “line printer.” ch08.indd 307 12/14/09 2:49:31 PM All-In-One / CompTIA Network+ Al...
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This note was uploaded on 04/27/2010 for the course COMPTIA 1201 taught by Professor N/a during the Spring '10 term at Galveston College.
- Spring '10