i met memdisk in relation to little boot-programs, mostly packaged as *.gz,
to load a boot-manager, a harddisk-checker or a memory-tester.
i guess it's something like a boot-floppy-emulation, am i right?
please correct me, if i'm wrong.
f.e. in my syslinux.cfg, based on boot-manager-entries that you can find in pmagic:
LABEL hdt
MENU LABEL ^A. hardware detection tool
TEXT HELP
An interactive hardware analyzer by Erwan Velu.
ENDTEXT
LINUX /boot/syslinux/memdisk
APPEND initrd=/iso/hdt.gz
LABEL memtest_86
MENU LABEL ^B. memtest86+
TEXT HELP
Check system RAM for errors.
ENDTEXT
LINUX /iso/memtest
LABEL supergrubdisk
MENU LABEL ^C. super grub disk
TEXT HELP
Easily restore grub-legacy. Boot into many systems. Fix Windows MBR.
ENDTEXT
LINUX /boot/syslinux/memdisk
APPEND initrd=/iso/sgd.gz
LABEL supergrubdisk2
MENU LABEL ^D. super grub2 disk
TEXT HELP
Boot into many systems (including Grub2 ones).
To restore Grub2 use the CLI suite included in PartedMagic.
ENDTEXT
LINUX /boot/syslinux/memdisk
APPEND iso raw initrd=/iso/sgd2.gz
LABEL mhdd
MENU LABEL ^E. mhdd
TEXT HELP
This software can make precise diagnostic of the mechanical part of a drive,
view SMART attributes, perform Low-level format, bad sector repair, different
tests and tens of other functions.
ENDTEXT
LINUX /boot/syslinux/memdisk
APPEND initrd=/iso/mhdd.gz
LABEL plp
MENU LABEL ^F. plop boot manager
TEXT HELP
The Plop Boot Manager is a small program to boot different operating systems.
The boot manager has a builtin ide cdrom and usb driver to access those hardware without the help/need of a bios.
ENDTEXT
LINUX /iso/plpbt.bin