I actually still use a quad core G5 with 16GB(!) of RAM, and 2x1TB SSDs for some audio production work in Logic 9.
64-bit started for me back when the G5 came out, and today that G5 screams, easily feeling as responsive as my girlfriend’s M1 MacBook Air most of the time.
It’s almost unbelievable how the G5 performs like it’s got bloody Sonic the Hedgehog trapped in there on a hamster wheel generator. My Intel machines never came close, and a lot of it seemed to have to do with major bloat as the OS moved along. Probably also bloat in Logic. My G5 can handle the hell of a lot more effects and VSTs with about 50% the impact they have on my Intel machines. It’s surreal.
I also find it absolutely pathetic and astounding that up until this year (16 inch MBP excluded) the maximum RAM a MacBook could have was the equivalent of a computer I got in 2005. 15 years later I still couldn’t get even 32GB RAM in a MacBook. And it was soldered so it couldn’t be upgraded. Shameful.
The 8 DIMM slots don’t fit in a laptop anyway ;) Seriously though, the 16GB limit was mostly due to the Intel parts not supporting more LP-DDR.
But yeah these things were beasts. The dual-CPU and then the dual dual-core were seriously impressive. I really wanted one at the time but could not justify it. I finally got one for €100 2 years ago, now it sits next to a G4 Cube. Both are some exceptional pieces of engineering.