[U-Boot-Users] My first embedded project

Wolfgang Denk wd at denx.de
Sat Feb 12 21:15:31 CET 2005

Dear Grant,

in message <528646bc050212001475fc6c92 at mail.gmail.com> you wrote:
> Wolfgang, regardless of the fact that the FAQ says that u-boot must
> run out of FLASH, in this scenario it will be running out of SDRAM. 

This is not quite correct. The FAQ says that it  *is*  possible,  but
you'd  better  understand  what  you  are doing. There are situations
(like flash- and ROM-less systems) where this is perfectly legal - or
even the only way to run any software at all. For example, consider a
PCI card  where  U-Boot  gets  loaded  into  pre-initialized  RAM  by
software running on the host computer.

The FAQ entry is intended to stop people with standard systems (i. e.
such booting from on-board flash) to use such an approach thinking it
would save them time or effort.

> Now, from what I know, I cannot see this being a problem because with
> the VIIPro+SystemACE there is no SDRAM initialization that the
> bootloader is responsible for.  Plus there is absolutely no FLASH
> device available anyway.  Do you see this as a problem?  If so, what
> are the likely issues that Roger may see?

I don't see any inherent problems.

> Note; BRAM may be expensive so it is desirable to keep it as small as
> possible; especially considering that the SystemACE loads the VIIPro
> via JTAG.  Big Image=Slow Boot.  I would make the first stage loader
> as dumb as possible.

Especially in such a situation it might make sense  to  include  zlib
functionality into the first stage loader - a compressed U-Boot image
will load faster (assuming your processor is fast enough).

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
In C we had to code our own bugs, in C++ we can inherit them.

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