[syslinux] Memdisk Ramdisk survive reboot

Dietmar Stölting dietmar.stoelting at t-online.de
Sat Jul 30 15:31:28 PDT 2005


Hi all,
I want to have a warmboot nonvolatile ramdisk to put and start XP  from ram.
That means that the ramdisk and its content have to survive a reboot on a
"normal computer"! (No battery ...hihi)
First I make a try with Microsoft ramdrive.sys and switch  /e in config.sys
from Dos 6.22 and with qemm386.sys but that doesnt work for me. Qemm (8,
97)does not work together with harddrive (only floppy) and syslinux.
Microsoft's ramdrive  DOESNT SURVIVE a reboot (for me). This is very angry,
because now I cant use ramdrive.sys for XP( which knows that driver well),
to make a ramboot with this attempt.

Then I rembered INT19, which can be enabled in Bios on my motherboard Asus
P4C800-E Deluxe.
INT 19 does a reboot without destroying the content of ram.
And that works: I installed Dos6.22 on a 100 MB FAT16 harddisk (first aktiv
partition). I copied a file called boot.com (type or paste pure hex thanks
to Brad 1986(!)

EB2A9051205520492043204B2042204F204F20540D0A2462792042726164205374657068656E
736F6E0D0A24B408B700CD108AFCB80006B90000BA4F18CD10B402B700BA2005CD10BA0301B4
09CD21B402B700BA1F0ECD10BA1701B409CD21CD19

in Hexeditor (Winhex12.25 is very good) and call it boot.com ) to that Dos
partition. After testing, that boot.com works which means that reboot to Dos
lasts 5 seconds, I enlarged this partition with Partition Magic to <2GByte
FAT16 because I need a large ramdisk and I have 4Gbyte ram. Then I make with
the Hexeditor an image of the whole <2GB partition including the first 63
sectors with mbr and call it dos.img  . I copied this image to another
harddisk.
Then I set up Syslinux 3.09 with memdisk on a >=2GB hardisk  as described in
syslinux.doc and memdisk.doc and copied the image dos.img on it. And this
boots with memdisk initrd=dos.img  (raw does not work)  to Dos even from a
USB harddisk, which can be removed(!) after booting without systemcrash.
When you type boot at commandline, it reboots and the content of that
ramdisk and the ramdisk itself survives! I am shure of this, because when
You use a USB harddrive and
disconnect it after first booting to Dos, NO harddrive is left!

Nice to hear from You
Dietmar






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