GET1M.COM

  Captures to disk the contents of adapter ROM and the BIOS in the area
  0xC0000 to 0xFFFFF in 64KB segments.

Target hardware:

  Old 8088/286/386 systems with the full ROM BIOS exposed at 0xF0000-0xFFFFF.

Not recommended for:

  - Newer 386/486/Pentium systems with ROM shadowing enabled.

  - Newer 386/486 systems where only part of the ROM is exposed in the
    0xE0000-0xFFFFF area.

  - Newer systems with compressed ROM (most systems today). These systems
    have the actual ROM contents at 0xFFFF0000 (4GB minus ROM size) and the
    code there decompresses itself to RAM at 0xF0000 and then uses the
    motherboard chipset to make it readonly.

  - Windows or OS/2 "DOS boxes". Windows mucks with the adapter ROM area and
    maps things in there like system structures, etc. A snapshot from within
    a DOS box would produce an incorrect capture.

Recommendations:

  - If you suspect there's more to the BIOS that provided in the "legacy" BIOS
    area, and the system is a 286, you may try the GET16286.COM program which
    uses the 286's protected mode to copy off the 0xFF0000-0xFFFFFF area
    (16MB minus ROM size).

  - Likewise for a 386SX, you may wish to use GET16M.COM program to capture
    the 0xFF0000-0xFFFFFF area (16MB minus ROM size) in case there is more
    exposed. Explanation: the 386SX only has an 24-bit external address bus
    and therefore can only access up to 16MB.

  - For a 486SX, try GET64M.COM to capture the 0x03FF0000-0x03FFFFFF region
    to see if it differs from the legacy area or the top of 4GB. Explanation:
    the 486SX has 26-bit external address bus and maxes out at 64MB.

  - Pentium or newer: Very likely the BIOS decompresses itself from ROM. Don't
    use this program, unless you KNOW for a fact that the BIOS is one of the
    few that doesn't shadow itself or decompress. Use the GET4G.COM program to
    capture from the 0xFFFF0000-0xFFFFFFFF region (4GB minus ROM size) where
    the actual ROM contents are mapped. You might run this program on such a
    system though if you wish to study what the decompressed ROM image looks
    like.

  - Modern CPUs with 36-bit or 40-bit external address bus: I'm not certain
    where the actual BIOS is mapped. I know that you can still read the BIOS
    from the top of the 4GB region as usual in most systems, but that might
    be a compatability map. I don't know if Intel continued the practice of
    resetting the instruction pointer to the highest memory address possible
    on CPU reset i.e. if modern CPUs fetch from an address like
    0xFF'FFFF'FFF0 (highest 40-bit address). You may be able to capture ROM
    using GET4G.COM (From top of 4GB), GET64G.COM (From top of 36-bit 64GB
    limit), or GET1T.COM (from the top of the 40-bit 1024GB limit).

