On Thursday, Aug 28, 2003, at 14:30 America/Chicago, Unsupported OS X wrote:
The good news is I can tell you Ryan plans on including Firewire booting and CD booting in the next upgrade of XPostFacto! It should come out soon after Panther OSX 10.3 arrives or maybe even sooner! I think Panther arrives in Sept sometime ?
I'm not sure I understand the CD part, I boot from CD already, and even an external Apple ROM SCSI CD player will boot. Perhaps you mean "any brand 'non-Apple' CD player" boot? As for Firewire booting, I'm not certain I see how Ryan could enable this with xPostFacto. My understanding is that the PRAM and NVRAM are very limited in size, and adding support for Firewire booting via PCI Firewire card seems like it would require way too much memory to be stored in these tiny bits of memory. Since the firmware ROM in unsupported Macs aren't flashable, where would the support be added, to a HD? I can't see how that would work, but let's hope you're correct. That would be fantastic. Thanks! Kris
The CD part is the ability to boot from special utility CDs, like the ones that are sometimes included in disk utilities and the like. (I.e. boot from CDs that are not Mac OS X Install CDs).
On the firewire booting, you're quite right that there isn't enough space in NVRAM to write a driver for the PCI cards. So what I'm doing is a bit of a trick, similar in principle to the trick that allows you to boot from an unmodified Install CD. Basically, I copy the kernel and kernel extensions from the Firewire drive to a drive that is actually bootable. Then, I set up the NVRAM settings so that the earliest part of the boot process loads the kernel and kernel extensions from the bootable driver (I call it the "helper", but I'm looking for a better word). However, the root-device is set to be the firewire drive. So, once the kernel and kernel extensions are loaded, the system actually boots from the Firewire drive. And it can read the Firewire drive at that point, because the kernel extensions are loaded that know how to do that. (The other tricky part is keeping the kernel and kernel extensions synchronized between the Firewire drive and the "helper" drive).
The other way it could have worked (and this would have been more elegant, but also more difficult to write), would have been to write a driver for the Firewire PCI cards and incorporate it into BootX. Then, Open Firmware could load BootX from a "helper" drive, and BootX could read the kernel and kernel extensions from the Firewire drive directly. In principle, this would be possible to do, but it would be complicated to figure out how to make it work.
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