So, I bring news. It turns out the "silent upgrade" minis (PowerMac10,2 clocked stock @1.33GHz and @1.5GHz) and the original release minis (PowerMac10,1 clocked stock @1.25GHz and @1.42GHz)
have non-trivial NewWorld ROM differences. For instance, the silent upgrade ones are solder-ready for the legendary 7448 processors (requiring just a small NVRAM-based patch, as with all 7448 upgrades for both Mac OS 9 and X), while the original release ones require custom ROM/Firmware/BootROM/NewWorld ROM patching first (VERY recently accomplished by dosdude1
here. And don't forget the NVRAM patch, too).
It does make me wonder if OS9 Firewire bootability could also be affected by this, as well as bootability from certain internal drives. I was certainly affected by the latter on my 1.5GHz mini as I had commented about at length in the past, and I also was not able to boot off FW like others were. (Have yet to test FW on an original release mini, though.)
So, yeah, by the way, put 7448s on your minis and clock them to at least 2.0GHz. And run OS 9, of course. Seek out CPU reballing/replacement services! Lots of them in the US, some of them in Europe, and hopefully some of them elsewhere in the world. My MDDs, PowerBooks and Mac minis eagerly await 7448 (and 7457) prowess.
Bless your OS 9 with a 7448 today! And have some love for 7457 and its L3 cache, too, especially on an MDD.