pc686 bsp for executables bigger than 1.44Mbytes

Chris Johns chrisj at rtems.org
Wed Jul 30 23:57:31 UTC 2008

John Pickwick wrote:
> Well, this PC is not connected to a network. I was more interested in 
> something like reading the executable from a hard disk or an USB memory as 
> Wendell suggested. I'm not a grub expert, do you think I can indicate the 
> path of an executable located on a USB device ?

Why not use qemu and not use real hardware ? The Wiki has details on using 
qemu. I do a great deal of development for RTEMS using qemu.

I only moved to a real PC so I could make sure the changes to RTEMS where 
tested on real hardware and with a real ATA (IDE) hard disk.

> Otherwise what would be the main steps to access the PC hard disk from a 
> "floppy-booted" rtems executable ? I have a FAT32 or NTFS format on it. I 
> guess I must declare some kind of ATA driver ?

RTEMS does support FAT but not NTFS. You could look at grub boot RTEMS from 
one of those disks. I have not done it but I assume it could.

You could also boot to DOS (or FreeDOS) from a floppy and have x.exe boot 
RTEMS. See http://www.rtems.org/wiki/index.php/Pc386.

To show how to get RTEMS to access a disk take a look at my test application. 
It shows how to handle the various file systems and mounts. It should make a 
suitable example. I use the shell and a shell init script to mount the various 


This example does expect a $(EXEEXT) makefile change for RTEMS that is 
currently not applied.


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