[syslinux] Memdisk lower memory usage

[Clay_Cooper at Dell.com]

Greetings,

I had a quick question about lower memory usage by memdisk. I've read
through the mail archives and found a couple of posted questions but
unfortunately no answers.  I know the documentation states:

"MEMDISK simulates a disk by claiming a chunk of high memory for the disk
and a (very small - 2K typical) chunk of low (DOS) memory for the driver
itself, then hooking the INT 13h (disk driver) and INT 15h (memory query)
BIOS interrupts."

However, running mem.exe after booting from my dos hd image via
pxelinux/memdisk and also after booting directly from the original
harddrive, shows that there is 77K less total available lower memory when I
boot using memdisk.

638K total available lower memory when booting from the actual harddrive.
561K total available lower memory when booting the image via memdisk.
BTW, in each case DOS is using 20K, leaving 618K and 541K of free memory
respectively.

Unfortunately, I've got a bios-update .exe that needs approximately
542K-578K lower memory to load, and I'm trying to pxe-boot into dos and run
it.  (Performing this via pxe is a necessity for a client).


I am calling memdisk and referencing the image (8.5MB uncompressed/ 4.5MB
compressed) with no special options in pxelinux.cfg/default.  

label dos
    kernel memdisk
    append initrd=dosboot.img  

I am using syslinux-2.04-1 on RH9 at the pxe server.  

Is this behaviour expected? Is there anything I can do to free up more
memory?  Thank you in advance for any advice you can give.

Respectfully,

Clay Cooper