RELIANCE 801421-4R电源模块
IBM PC/AT计算机通过将第二个从属PIC级联到原始主PIC中，又增加了八条IRQx线，编号为IRQ8到IRQ15。主PIC处的IRQ2作为从PIC的级联输入。该架构如第49页图3-1所示。为了保持与PC/XT系统的向后兼容性，IBM选择在从属PIC上使用新的IRQ9输入作为PC/XT扩展总线上的旧IRQ2中断线。因此在AT系统中，IRQ9中断线连接到AT扩展总线（或ISA总线）上的旧IRQ2引脚（引脚B4）。VMIVME-7740 VMEbus接口使用的奇偶校验错误（必须在BIOS设置中启用）0 BIOS设置设置的系统计时器1 BIOS设置设置设置的键盘2与IRQ9 3 COM2/COM4 4 COM1/COM3 5分配给板上计时器的计时器6软盘控制器7 LPT1不可用8实时时钟9旧IRQ2由BIOS确定
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
