INT 15 - EISA SYSTEM ROM - READ PHYSICAL SLOT
AX = D804h
CL = slot number (including embedded and virtual)
Return: CF clear if successful
AH = 00h
CF set on error
AH = error code
80h invalid slot number
83h empty slot
86h invalid BIOS-FW function call
SI:DI = 4-byte compressed ID (DI = bytes 0&1, SI = bytes 2&3)
Note:   call with AL=84h if using 32-bit CS addressing mode instead of 16-bit

See also: 15D800

15D804 - EISA SYSTEM ROM - READ PHYSICAL SLOT