I remember such a program, but I do not know its name.
I had to use Ctrl-Shift-Shift as hotkey.

you can do it with int 0x19 but it rarely works because of hooked interrupt handlers. qemm used to have a warm reboot mechanism that was more reliable.

Could Indeed be it was quemm. Would be great if that function would be available as dedicated executable.

Later QEMM versions did that fast boot stuff. Ctrl+Alt+Delete skips the POST and goes directly to Starting MS DOS...
It was nice, but sometimes it caused issues and you had to reboot while rebooting to do a full POST and force reinit of some crazy stuff (e.g. a hanging Adlib sound).

Lilo can be abused for this.

It is able to be told to start an msdos boot sector, from the command line.

BloodyCactus wrote on 2025-10-30, 16:01:

you can do it with int 0x19 but it rarely works because of hooked interrupt handlers. qemm used to have a warm reboot mechanism that was more reliable.

Exactly!

I actually have a tool to do it.

it runs a bootsector to grab all the original int vectors, then you run the stage2 tool which creates the tsr and hooks int19 and puts all the vectors back.
once it has the vectors, you dont need the bootdisk anymore to capture them. once you have the generated warm.com its specific to your machine and off you go!

things like himem.sys can break it tho.

https://bloodycactus.com/files/warmboot.zip

Great thanks. Although it’s sounds a bit like black magic I Will definitely try. 😀

Be aware that flushing caches is a good preventive measure to avoid data/filesystem corruption, and you should also attempt to notify any network stack that could possibly be active, the same goes for any DOS multitasker. Later, reset the drive. And then finally, perform the fast reboot, which despite all these precautions, might not be safe due to interrupt interceptions, as mentioned above.

IMHO, best is to perform a cold reboot and live with the burden of a couple of additional seconds for the boot process to end, than to risk system integrity.

Yes indeed. Cache flush is necessary in case you don’t use /x option.

Especially when you are really testing a lot configs etc it gets annoying with that long reboot time 😀

Feedback: unfortunately not working for me. Although I followed the instructions reboots are as usual.

But thanks for providing the test example.

Marco wrote on 2025-10-30, 14:44:

hello all, […]
Show full quote

hello all,

I might be wrong but I roughly remember that some programs / OS were able to reboot directly to the boot init sequence. (Not to post/bios but directly to „starting msdos“.

Am I right here? If yes do you know any program / executable to do so?

Thank you

Back then: "Using Grub4Dos I managed to start windows 2000 from the Dos prompt without a BIOS reboot.". Would that help?

Thank you. I will have a look. Do you have a specific configuration file to share maybe for grub?

Marco wrote on 2025-11-10, 23:09:

Thank you. I will have a look. Do you have a specific configuration file to share maybe for grub?

I just found it again
HDD chainloader for DOS?

C:\GRUB4DOS\GRUB.EXE --config-file="root (hd0,0);chainloader +1"

Just wanted to say thanks.
Grub4dos couldn’t help because there is no way to go-back-to-grub via warm reboot key combination (needed eg after freeze or config changes).

It indeed can initiate the boot from another drive / partition though.

Again thanks for that idea

you can try this in debug:

C:\debug
-a100
mov ax,40
push ax
pop ds
mov bx,072
mov word ptr [bx],1234
mov ax,ffff
push ax
xor ax,ax
push ax
retf
-nwarmboot.com
-rcx
14
-w
-q
C:\warmboot.com

This is an all-in-one reboot and shutdown program for DOS that works on any
PC, even on ancient 8088 XT and, of course, on a modern ATX one where it
actually powers down the system.

The reboot variants, was code I decided to merge to SHUTDOWN since the data
corruption prevention process is basically the same.

Before any shutdown or reboot occurs, SHUTDOWN will first flush DOS cache
programs, and then perform a DOS file system and disk reset routine on all
available drives.

Please always remember that the SHUTDOWN command MUST have its parameter in
uppercase. Failure to do so will result in no reboot or shutdown operation and
having the command line help text being displayed (which actually tells you to
do things the proper way!).

Partial list of DOS Cache programs that get to be flushed before any shutdown
or reboot:
CD Blitz, Norton Cache, Novell NWCACHE, PC-Cache, PC Tools, QCache,
QuickCache, SmartDrive, Super PC Kwik, and plenty others that have a routine
checking interrupt 13h.

Be aware that there cannot technically be a safe 100% perfect way to stabilize
a DOS system for a proper shutdown or reboot, as interrupts may have been
captured and or be monitored by resident programs that no one can predict
what they might be doing or how to address them. However, SHUTDOWN attempts
to follow common good practices that can "almost always" lead you to a safe
path. SHUTDOWN is indeed much better than pulling the power cord and praying
for the best outcome when it comes to your precious data!

----------------

SHUTDOWN - Powers off or reboots this computer.
Version 2.02 - Copyright (C) Ignacio F. Gully

Syntax:
SHUTDOWN [/Y] [/R] [/W] [/F]

Options:
[/Y] Shuts down the system.
[/R] Cold system reboot.
[/W] Warm system reboot (Not recommended).
[/F] Fast system reboot (May crash your computer. You have been warned!).

Note:
Parameters must be uppercase.

----------------

SHUTDOWN is Public Domain software.
Binary release only.

Ignacio F. Gully
SHUTDOWN's author

igully wrote on 2025-11-27, 05:28:

This is an all-in-one reboot and shutdown program for DOS that works on any PC, even on ancient 8088 XT and, of course, on a mo […]
Show full quote

This is an all-in-one reboot and shutdown program for DOS that works on any
PC, even on ancient 8088 XT and, of course, on a modern ATX one where it
actually powers down the system.

Parameters must be uppercase.

Hi Ignacio,
nice tool.
Perhaps you can include mkarcher's code to park the Dallas chip. Because the real time clock will be halted it is ideal when you put that retro computer back into the shelf, greatly increasing battery life and still keeping the CMOS contents intact.
It should be combined with your /Y parameter.

Conserving Dallas RTC chips

And please accept lowercase parameters too 😀

Thanks,
Gregor

Hi Gregor,

I did not know it was possible to do such thing to Dallas RTCs. It is cool. I have added the procedure to shutdown. Thank you for pointing it out.

I thought that requiring uppercase parameters was a more "secure" way to let users think their decisions over. Perhaps I was being too paranoid. Parameters are now case insensitive.

I also added Novell NetWare and Microsoft Network Client notifications.

Thank you for your feedback. New version 2.03 incorporating all these changes is right here below.