Re: [ECOS] Redboot (i386pc with IDE Flash)

[Nick Garnett <nickg at ecoscentric dot com>]

David Brennan <eCos@brennanhome.com> writes:

> Nick,
> Can you easily summarize why redboot does not work with GRUB? This is
> a feature that I am going to be looking for in the near future. Is it
> just something that no one has tackled? Or is it impossible for some
> reason? I am working on a VME based PC and have several available
> target machines, but only one floppy. So I want to be able to boot off
> of CF and still load/debug using Ethernet. If this is possible but
> just needs work, can you give me some pointers as to what needs to be
> done?
> 

RAM applications load at the 1MB boundary, so RedBoot needs to live in
the bottom 640k. However, GRUB also uses the bottom 640k, so we would
need to load a GRUB RedBoot above the 1MB boundary. This means that we
would then have to shuffle RAM applications up, probably to 2MB. This
causes an incompatibility, and also means that when not using a GRUB
RedBoot, we waste a megabyte of memory.

We also end up with the silly situation of using a bootloader to load
a bootloader to load the application. It was thought much better to go
straight to the application from GRUB. RedBoot on the PC has much less
functionality than elsewhere since there is no flash. All it can
provide is loading an application from the network, and GDB
support. GRUB can load from the network, and by building the stubs
into the application we get GDB support. So RedBoot is largely
redundant, and no effort has been put into making it work.


-- 
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com/     The eCos and RedBoot experts


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