>> The most modern (i.e. newest) card so far reported to work
>> with MorphOS in PCIe-based PowerMac G5 is the Radeon HD5450
>> from 2010, which also works in 3D with the latest TinyGL beta.

> I have the Apple X1900 card. I thought it and the PC X1950 were
> the best it would do.

As ernsteiswuerfel wrote, this depends on the meaning of 'best'. You wrote "most modern", which I thought to refer more to feature set (newer standards etc.) than to speed.

> I do have a PC HD5450 new in the box though.
> Are you sure this works in the G5 PCI-E?

You may try. Some cards work and some don't, and nobody seems to know why.

> Isnt this HD5450 lower end card?

Yes, it's a low-end card from a more modern (4 generations) series of cards than Radeon X1000 series.