>In fact, I've been waiting for a chance to ask whether Apple's BootROM is
>ROM at all!  A design which copies NVRAM into RAM, boots an operating
>system, erases the RAM copy of NVRAM, and then potentially rewrites the
>NVRAM seems like insanity to me, but apparently there are many PC BIOSes
>that work the same way.  (I thought they were designed to have a
>non-flashable area of ROM, so that you couldn't shoot yourself in the foot.)
>
>-- Derek

The BootROM is not ROM. You can shoot yourself in the foot (been there,
done that, sent the machine to Apple..).

As far as I know the operating system can not write normally
on the bios area, there *is* some kind of protection against that
once the system has booted, infact to upgrade the bios you have
to reboot with the programmer button pressed. Problem is that this
protection doesn't take place when booting the system, who has tried
playing with load-base and load-size knows it.

The NVRAM is copied to RAM for performance reasons, and then is
freed to save RAM. Having a minimal failsafe firmware flasher
placed in real rom (Like and AlphaPC does, in example) is an idea
that Apple did not have, or if they did at least they didn't disclose
any information on how to use it.

I mean that I can't believe that Apple writes the firmware on the
flash/nvram/whatever before soldering it on the motherboard, and when
my poor G4 did come back "repaired" they neither had changed the MB
nor had replaced any chip... in some way they just reflashed the bios.

Regards,

Andrea

-- 
Andrea Cocito
Director of the Biocomputing Research Unit
Department of Experimental Oncology
Europen Institute of Oncology
Via Ripamonti 435, Milano - Italy
Tel. +39-02-57489857
Fax. +39-02-57489851