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 😀