The double chime is totaly normal.  It has something to do with resetting
the nvram, at least that is what the linuxppc developers say.

Aaron Jackson

>> Does that two-stage boot process you described explain why I got two boot
>> chimes from my machine before I got a command line prompt?  Or was that
>> some kind of failure followed by a retry which worked?  (PowerMac 8500,
>> boot floppy image from the last month or two.)
>>
>
>In response to this one, I have had the same trouble with my PowerMac 8600/300.
>I believe that it boils down to a tired power supply. My machine takes forever t
>o get from the black screen (and chimes) to get to any kind of operating system.
> Running LinuxPPC, my machine rechimes (is that a word?) 3 times before it start
>s to boot. If I'm wrong on this please correct me. I'd really like to take care
>of this problem on my box as well.