Re: "Hello, Dawn!" protected mode boot sector

look and see wrote:
This is the "Hello, Dawn!" protected mode boot sector with no bios calls.
It's written in 32 bit assembly language, and uses the 640X480X16 graphics mode.

Some folks are a little cautious about running binaries from an unknown (no offense) source. We can disassemble it, of course - PITA disassembling mixed 16/32 bit stuff... (you appear to be doing lgdt without setting ds, which is going to work only on biosen that boot with ds=0, unless I'm mistaken)

After executing the minimum five real mode instructions required to enter protected mode, the floppy disk motor is turned off, the graphics mode is changed, the screen is cleared, and the resident 8X16 rom font is located and used to print "Hello, Dawn!" to the screen.
"press any key!" to reboot the PC. No bios calls are used at any time.

This improved version includes a better search routine to locate the font and a better method of resetting the PC.
The code is optimized for a Pentium class machine (no delaying for input/output instructions), using only the 80386 instruction set.
The graphics resolution is the highest available without video bios calls.

Very impressive. But where do you go from here? The only sane thing for a bootsector to do is load something else. Have you got a way to do that from pmode?

The boot sector image is available at http://parallelos.com/HelloDawn/BOOTIMG.BIN
The file size is 512 bytes plus an 80 byte file footer for the copyright notice.

Hmmm, all I've got is 512 bytes even... Does the license even allow me to disassemble the thing?

The image file can be used as named to create a 1.44 MB floppy disk emulation bootable CD.

Got any easy instructions for making a bootable CD? (my machine won't boot from CD anyway, but it's an interesting technique) I just wrote it to a real floppy. It's the kind of thing a cautious person would run only in emulation.

Mike Gonta - mikegonta@xxxxxxxxxxx
look and see - many look but few see


"Seeing is believing. If you didn't believe it, you wouldn't have seen it!"

Best,
Frank
.