On Aug 6, 2008, at 2:46 PM, Wolfgang Denk wrote:
In message 20080806193205.GA3975@ld0162-tx32.am.freescale.net you wrote:
It's hit me before when I foolishly try to load something at address zero -- why do we put u-boot at the end of RAM, and put up with the relocation weirdness, if not to allow loading things at zero?
We want to free as much memory as possible. But low RAM cannot be made available on all systems.
Well, one reason might be to have identical code for all PPC systems ?
It's already 85xx-specific code.
Good point. Why don't we factor this out and make it common code for all PPC?
Because the relocation is specific to the various interrupt types. Book-E will need different code for handing IVPR/IVORs than classic.
Not only 6xx. Actually all PPC.
No, not all PPC. Book-E exceptions are different.
Maybe. But then, these can use exception vectors at low mem, too, right?
They can, but it has to be setup.
For me the chance to have common code (and identical behaviour) for all PowerPC processors is much more important that being able to use 16 kB additional memory on one specific family of processors.
- k