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I'm doing some work with the CP/M-86 source code, for a small little project in pure asm, and I basically want to create a DOS that will run on PC's, XT's, AT's, and PS/2's with 386's.

The thing is, all of these bootloader tutorials talk about how to enter protected mode and then do things there... but I want to know how to make a real-mode bootloader that'll look for my substitute CPM.SYS and then go from there.

From reading CP/M documentation, I know how to actually load the kernel into memory, but what do I do before that? What does it take to write an 8086 bootloader?

Thanks

Hm: how about just fetching the image from floppy/hd, putting it where you want it to be and jump to its entry point to do the rest there? Simply don't activate protected mode and don't care about GDT and IDT - don't even touch the corresp. registers.

HTH & CCW

I would normal say get bootprog.zip http://alexfru.chat.ru/epm.html
But link is down .
This is a program that fits on the boot sector and loads a bin, exe, com ,sys file from a fat12 floppy, with nasm code, by a certain name.
If the link is still down let me know and i will send you a copy.

\\\\||////
(@@)
ASHLEY4.

Batteries not included, Some assembly required.

ASHLEY4 wrote: I would normal say get bootprog.zip http://alexfru.chat.ru/epm.html
But link is down .
This is a program that fits on the boot sector and loads a bin, exe, com ,sys file from a fat12 floppy, with nasm code, by a certain name.
If the link is still down let me know and i will send you a copy.

\\\\||////
(@@)
ASHLEY4.

Batteries not included, Some assembly required.

The link appears to still be down. This is pretty much what I'm looking for... I think the system files will be in the .SYS format so... it should work. Thanks!

Try here: http://board.flatassembler.net/download.php?id=1315
you will need to change the load file from a bin to a sys and the name must be 8 letters and 3 ext.
eg: "MyKernel.sys"

good luck.

\\\\||////
(@@)
ASHLEY4.

Batteries not included, Some assembly required.