键盘中断向量的获取

    #define IO_APIC_BASE 0xFEC00000 // I/O APIC Physical Base Address
        PHYSICAL_ADDRESS IOAPIC_AREA;     // i/o apic mapped pointer

    //
    //  Connect physical memory 0xfec00000 to [MappedVirtualVariable]
    //
    
    IOAPIC_AREA = RtlConvertLongToLargeInteger(IO_APIC_BASE);//物理地址0xFEC00000处储存着IDT的,硬编码
    PULONG IOAPICGate = MmMapIoSpace(IOAPIC_AREA, 0x40, MmNonCached);    
    
    //********************************************************************************************
        
        IOAPICGate[0] = 0x10 + 2 * IRQ + 1;
    Buffer = IOAPICGate[4];
    IOAPICOldHighbyte = Buffer; // save it for clean-up

    Buffer = 0; // Physical Destination APIC ID with 0x00
    IOAPICGate[0] = 0x10 + 2 * IRQ + 1;
    IOAPICGate[4] = Buffer; // write

    IOAPICGate[0] = 0x10 + 2 * IRQ;
    Buffer = IOAPICGate[4];
    IOAPICOldLowbyte = Buffer;

    Buffer &= 0xFF;  // now buffer has the vector value
    IOAPICKeyboardVector = Buffer;

    DbgPrint("Keyboard Vector :: 0x%x\n", Buffer);

    // Delivery Mode [10:8] to 111b (ExtINT)
    // Destination Mode [11] to 0 (Physical)
    //
    Buffer = Buffer | 0x700; // Vector(may be 0x93) + ExtINT + Physical Destination + High active + Edge sensitive + non masked
    IOAPICGate[0] = 0x10 + 2 * IRQ;
    IOAPICGate[4] = Buffer;        // write

    上面的这些代码，我基本能猜到是什么意思。但是我没有相关的manual。其实我找到了manual，不过是过时的，与上面的不符。


    对IOAPICGate[0]的写入，对IOAPICGate[4]的读取究竟是怎么回事，请高手来解释一下，做好提供inlel的manual。