Normally, the "Extended BIOS Data Area" (EBDA) is located at the segment stored at
0x0040:0x000E, but this is only true for EISA and MCA systems (at least that's what I found in various specs). This BDA Map says that on older systems, the word at
0x040E is "LPT 4 port address", while on PS/2 systems it is indeed the EBDA segment.
How can you find out the location of the EBDA in older systems, and how can you find out that
0x040E points to it and is not describing something else?