I seem to remember either Ralph or Gerald saying that SmartFirmware used "conservative settings" (possibly on Ann.lu). Andreas has already made that point here well too: stability is preferable to speed.

Made perfect sense back then. Less annoyed users, fewer boards being RMA'd because of RAM incompatibilities, and it was not like a G3/G4 was going to be running high end RAM-intensive stuff even in early 00s, not that the Marvell bridge chips could handle it very well in any case.

Unfortunately the inability to play around with timings and looser tolerance on voltages than present day means you're probably going to have to try a lot of DIMMs blind. That sucks, but then the hardware is two decades old. Imagine trying to find working cards and RAM for a 286 PC around the year the Peg-2 came out.