INT 1A - Intel PCI BIOS v2.0c - INSTALLATION CHECK
        AX = B101h
Return: AH = 00h if installed
            CF clear
            EDX = 20494350h (' ICP')
            EDI = physical address of protected-mode entry point (see below)
            AL = PCI hardware characteristics
                bit 0: configuration space access mechanism 1 supported
                bit 1: configuration space access mechanism 2 supported
                bits 2-3 reserved
                bit 4: Special Cycle generation mechanism 1 supported
                bit 5: Special Cycle generation mechanism 2 supported
                bits 6-7 reserved
            BH = PCI interface level major version (BCD)
            BL = PCI interface level minor version (BCD)
            CL = number of last PCI bus in system
        EAX, EBX, ECX, and EDX may be modified
        all other flags (except IF) may be modified
Note:   this function may require up to 1024 byte of stack; it will not enable
          interrupts if they were disabled before making the call
SeeAlso: AX=B181h

Call protected-mode entry point with:
        registers as for real/V86-mode INT call
        CS = ring 0 descriptor with access to full address space
Return: as for real/V86-mode call

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