Although the standard installer gave me this same error, the legacy
installer worked fine.

Tony Richardson

On Jan 4, 2017 10:18 AM, "Jerome Shidel" <> wrote:

> On Jan 4, 2017, at 9:16 AM, Tony Richardson <>
> I am having exactly the same problem (Invalid Opcode at HIMEMX line) with
a laptop from the same era.  FreeDOS 1.1 installed without problems.  I was
using the 1.2 standard CD.  I plan to try the 1.2 legacy CD tonight to see
if that makes a difference.  (Is there a description of the differences
between the standard and legacy installation CDs somewhere?)
> Tony

Yes. I've gone into the details in the FreeDOS-devel list and on Facebook
previously. But, don't think I've described it here.

Basically, the CD images are identical and install the exact same version
of FreeDOS. However, there is one major difference. The use different
booting methods. The Legacy (LGCY) version uses the original El Torito
bootable CD specification. To boot this CD, the system BIOS loads a image
file from the CD and uses it to emulate a floppy disk and boots it. The
normal FD12CD.iso is handled differently. It boots a binary image file for
ISOLINUX, this in turn uses memdisk to load and emulate a floppy for

Some systems behave erratically with one or the other method. For example,
the LGCY disc will appear to function correctly under VirtualBox. But, when
any program then access the data portion of the disc, the system freezes.
VirtualBox requires the FD12CD. But, some users have reported that method
did not work on their hardware and the LGCY version worked fine. These two
methods are mutually exclusive and cannot be combined without breaking
system compatibility with machines that only support the original
specification. So, both versions are required for maximum compatibility.

By all rights, any computer that supports booting from CD, should work with
the LGCY version. But, that is not the case. It may be the result of BIOS
vendors not fully testing their compatibility with the ancient CD boot
spec. But, it could be elsewhere.

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