RELIANCE 801421-4R電源模塊
IBM PC/AT計算機通過(guò)將第二個(gè)從屬PIC級聯(lián)到原始主PIC中，又增加了八條IRQx線(xiàn)，編號為IRQ8到IRQ15。主PIC處的IRQ2作為從PIC的級聯(lián)輸入。該架構如第49頁(yè)圖3-1所示。為了保持與PC/XT系統的向后兼容性，IBM選擇在從屬PIC上使用新的IRQ9輸入作為PC/XT擴展總線(xiàn)上的舊IRQ2中斷線(xiàn)。因此在A(yíng)T系統中，IRQ9中斷線(xiàn)連接到AT擴展總線(xiàn)（或ISA總線(xiàn)）上的舊IRQ2引腳（引腳B4）。VMIVME-7740 VMEbus接口使用的奇偶校驗錯誤（必須在BIOS設置中啟用）0 BIOS設置設置的系統計時(shí)器1 BIOS設置設置設置的鍵盤(pán)2與IRQ9 3 COM2/COM4 4 COM1/COM3 5分配給板上計時(shí)器的計時(shí)器6軟盤(pán)控制器7 LPT1不可用8實(shí)時(shí)時(shí)鐘9舊IRQ2由BIOS確定
The IBM PC/AT computer added eight more IRQx lines, numbered IRQ8 to IRQ15, by cascading a second slave PIC into the original master PIC. IRQ2 at the master PIC was committed as the cascade input from the slave PIC. This architecture is represented in Figure 3-1 on page 49. To maintain backward compatibility with PC/XT systems, IBM chose to use the new IRQ9 input on the slave PIC to operate as the old IRQ2 interrupt line on the PC/XT Expansion Bus. Thus, in AT systems, the IRQ9 interrupt line connects to the old IRQ2 pin (pin B4) on the AT Expansion Bus (or ISA bus).Parity Errors (Must be enabled in BIOS Setup) Used by VMIVME-7740 VMEbus Interface 0 System Timer Set by BIOS Setup 1 Keyboard Set by BIOS Setup 2 Duplexed to IRQ9 3 COM2/COM4 4 COM1/COM3 5 Timer Assigned to On-Board Timer 6 Floppy Controller 7 LPT1 Not Available 8 Real-Time Clock 9 Old IRQ2 Determined by BIOS
