"Reserved" means it cannot be used by you for extension card assignments. So, for example, the IRQs shown for Com1 or Com2 could be used for something else if you don't have a com port in use.
IRQ assignment (notes) 0 timer (reserved) 1 keyboard (reserved) 2 interrupt 8-15 (reserved) 3 Com4 or Com2 (ports can share the IRQ if both are not in use at the same time) 4 Com3 or Com1 (ports can share the IRQ if both are not in use at the same time) 5 2nd parallel port (LPT2: The second printer port) 6 Floppy drive contr. (It you don't have a floppy drive controller, this IRQ is available) 7 1st parallel port (LPT1: (or PRN:) The first printer) 8 real-time clock (reserved) 9 **** (unassigned) 10 **** (unassigned) 11 **** (unassigned) 12 **** (unassigned) 13 math co-processor (reserved) 14 Primary HD controller (drive 0 and 1) 15 Secondary HD controller (drive 2 and 3; can be used if you dont have a second controller)
IRQ IO BASE DMA the usual assignment * 200-207 * Game port 2 330 * MPU-401 Emulation (PAS 16) 3 300 * 3Com Etherlink II, II/TP, II/16, II/16TP, 16/16TP 3 300 * Novell NE2000 3 300 * SMC/Western Digital 8003EP, 8013EWC, 8013WB 5 368 * Ungermann-Bass Ethernet NIUpc (long), NIUpc/EOTP (short) 5 ??? * DEC etherWORKS LC, Turbo, Turbo/TP 5 220 1 Sound Blaster Emulation (PAS 16) 5 220-22F 1 Sound Blaster 2.0 (default) * 338-339 * Sound Blaster 2.0 FM music chip 7 * 3 Pro Audio Spectrum 16 (PAS 16) 9 300 5 Boca Ethernet BEN100, BEN102, BEN300
The default IRQ/DMA settings for XT systems vary from these.
from, Ralph Valentino (ralf at wpi.wpi.edu) Hardware Engineer, Worcester Polytechnic Institute