Daniël's PowerPC BGA chip swaps

[Coloruser]

I wonder if that might play a role in the CPU card compatibility?

Yes it does. Some cards only work within the „simpler“ Tanzania L2 Slot as they can boot directly from there because of the differences in slot design you have outlined above. For Gazelle and Alchemy, a card needs to have a CPLD to do some bus magic to take over the CPU bus after initialization by a Mac OS init. Earlier cards could only do either or. Later ones were combined design. The company I worked for only commercialized the Tanzania one - first of all because we also sold Tanzania clones and that market was bigger than Alchemy/Gazelle thanks to all the Moto clones. And honestly, we never were able to get the Alchemy version to a point, where is was stable enough in all boards (Power Computing, Umax/Supermac, Apple Alchemy/Gazelle). We had no complete schematics those days and had to probe pins and do trial and error. It was too time consuming and higher priority developments needed work, too.

 

[Daniël]

Did you get this board from last year working well? Those chips have a later date code than the ones I've tried. How high do they clock?

I haven't installed the QFP cache chips yet, it's on the eternal backburner at the moment.

Yes it does. Some cards only work within the „simpler“ Tanzania L2 Slot as they can boot directly from there because of the differences in slot design you have outlined above. For Gazelle and Alchemy, a card needs to have a CPLD to do some bus magic to take over the CPU bus after initialization by a Mac OS init. Earlier cards could only do either or. Later ones were combined design. The company I worked for only commercialized the Tanzania one - first of all because we also sold Tanzania clones and that market was bigger than Alchemy/Gazelle thanks to all the Moto clones. And honestly, we never were able to get the Alchemy version to a point, where is was stable enough in all boards (Power Computing, Umax/Supermac, Apple Alchemy/Gazelle). We had no complete schematics those days and had to probe pins and do trial and error. It was too time consuming and higher priority developments needed work, too.

This does tempt me to try and rewire an Alchemy or Gazelle board to have the missing/different signals patched back in, just to see what happens.
It's a bit above my paygrade, trying to figure out if it's just the way things are wired up that makes it work, or if firmware specific tweaks are also present in Tanzania, vs. Alchemy/Gazelle.