Re: multiboot2: variable data size

[Hollis Blanchard]

On Sat, 2006-11-25 at 04:46 +0100, Yoshinori K. Okuji wrote:
> On Saturday 25 November 2006 04:33, Hollis Blanchard wrote:
> > That's exactly the point: there will be no difference. Both
> > architectures will use 64-bit types.
> 
> No. Both should use 32-bit, because GRUB transfers control in 32-bit mode. 
> Passing 64-bit addresses would be useless in this case. Note that the memory 
> map information is 64-bit even in the previous version of Multiboot Spec.

OK, I don't have a problem with this. We should clarify the spec. 
It will limit e.g. module sizes and addresses to less than 4GB, but
practically speaking I don't think that is too big a deal.

However, there are 32-bit architectures that support 36-bit addressing
(PowerPC is one of them). In some cases, physical IO is above 4GB, so
some other data structure would be required to identify those devices.
So we must remember that multiboot will not be adequate to describe an
entire system like the Open Firmware device tree does.

Do we really need x86_64-pc's "bit 17", which specifies that 64-bit
addresses are required?

-Hollis