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Produkte » µnOS » Dokumente » Bootloader
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1. Basic Idea
The fundamental idea of the miray bootloader is to keep the inflexible and cramping part of the
boot-engine as small as possible.
So this part, called bootloader (in contast to the sysloader),
is separated from the rest to achieve the highest possible flexibility for the whole boot-engine.
2. Independence
The bootloader is the only part that must be on the machine when booting
µnOS.
The bootloader knows where to load the sysloader from.
After the sysloader is loaded and initialized, it does the rest of the system-initialization,
loads the system (there its name comes from) and brings it up.
3. Implementation
The bootloader corresponds to the bootsector of PC compatible computer systems.
On a computer system with a standardized bootsector, the miray bootloader would
be the executable part of the bootsector.
The miray bootloader is independent of a standardized bootsector format!
The only thing that's neccessary is that the bootloader is located or loaded to a predefined
memory address at startup.
This can be RAM, Flash-Memory or ROM or any other technology
that's based on random access.
On the PC platform, it's the RAM solution, as the bootsector is loaded automatically to
a specific memory address on these systems.
4. Requirements
And as our current bootloader for PCs needs only 222 bytes of memory (on disk as well as in RAM), there is plenty of space left, so that it can support
FAT formatted disks without overwriting the FAT info in the bootsector.
The 222 bytes of bootloader code (tiniest configuration) could also be burned into ROM
and then it wouldn't even be neccessary for the system to have a drive of any kind.
5. Versatility
Once the miray bootloader is activated, it can boot the system from
- floppy,
- harddisk (SCSI/IDE),
- CD-ROM,
- network (ethernet),
- serial port (RS-232),
- parallel port
or from any other data port in the system.
6. Scalability
The miray bootloader is designed to fit smallest embedded systems.
But on the other hand, there is no limit of scalability,
as the bootloader initializes the sysloader, a normal executable file,
so that complex, interactive boot sequences for huge systems also can be realized easily and
comfortably.
The miray bootloader allows to boot µnOS on systems which have a minimum of hardware
equipment and without preinstalled software.
This is the basis for running µnOS on the tiniest embedded systems.
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Bootloader appearance