Summary

42 IT Essentials: PC Harware and Software Companion GuideTable 1-11 I/O Addresses continuedTypical Typical TypicalI/O Port Device or I/O Port Device or I/O Port Device orAddresses Port Addresses Port Addresses Port(in Hex) Assignment (in Hex) Assignment (in Hex) Assignment070–071 CMOS/real- 2E8–2EF COM 4 E800–E87F Fast Ethernettime clock serial port adapter0F0–0FF Math 2F8–2FF COM 2 F000–F00F IDE controllercoprocessorserial port130–14F SCSI host 376–376 PCI IDEadaptercontroller170–177 Secondary 378–37F LPT1hard-diskcontrollerDirect Memory AccessHigh-speed devices use Direct Memory Access (DMA) channels to communicate directlywith the main memory. These channels allow the device to bypass interaction with the CPUand directly store information in memory and retrieve it. Only certain devices can beassigned a DMA channel, such as SCSI host adapters and sound cards. Older computershad only four DMA channels to assign to components. Newer computers have eight DMAchannels that are numbered 0 to 7, as shown in Table 1-12.Table 1-12DMA ChannelsDMAChannel Default Device Can Also Be Used For0 Dynamic RAM memory refresh1 Sound card (low DMA setting) Network cards, SCSI adapters, parallel printingport, and voice modems2 Floppy disk controller3 Available Network cards, SCSI adapters, parallel printingport, voice modems, and sound card (lowDMA setting)4 Cascade for DMA 0–35 Sound card (high DMA setting) Network cards, SCSI adapters6 Available Network cards, sound card (high DMA setting)7 Available Network cards, sound card (high DMA setting)