> the only relevant photo I could find on the net is this one

The archived FastMac website has more photos.

> claiming to be indeed a FastMac

I just found you reported on your "FastMac 1.6Ghz G4 7451" already two years ago :-)

> If the above are true then this is a 7455 @ 1.53Ghz (?), hence there is a
> chance that MorphOS could be reporting both cpu and clock wrong, wtf?

According to the DIP switch table on page 4 of the installation guide, the 7455 on the card can be clocked up to 1.50 GHz on 100 MHz bus machines and up to 1.53 GHz on 133 MHz bus machines, so 1.50 GHz should be maximum on your Sawtooth. Either way, both "7451" and "1.6 GHz" seem (slightly) wrong.

> this must be a cpu with a massive L3 cache

Both 7451 and 7455 can support up to 2 MiB L3 cache, and according to the above-linked website, the 7455 on the card is fully equipped.