From: Jerome Shidel <>

> 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 booting.

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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