error: core image is too big (0xXXXXXX > 0x78000)

[Glenn Washburn]

This only happens on i386-pc and i386 pxe.

Can anyone explain or point to documentation as to why the core image
can't be larger than 0x78000 for i386?

It appears that this check is to prevent grub from occupying some of
the upper memory area.  Why can't grub use the upper memory?  Why
doesn't grub use unreal mode to access the extended memory?  If it does
use these memory regions, why is there this limit?

Any insight is appreciated,
Glenn