[U-Boot-Users] My first embedded project

[Grant Likely]

On Sat, 12 Feb 2005 21:15:31 +0100, Wolfgang Denk <wd at denx.de> wrote:
> 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.

Right; understood.

> > 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).

Good idea.  Fortunatly once the first stage is loaded the processor is
started and JTAG is no longer used.  Loading the second stage should
be quite quick.

Cheers,
g.