not sure where this should go, so figured id plonk it here, but thanks to
@r6mile I recently got my hands on an ATI Radeon 2600 XT from a MacPro3,1 I have wondered for a long time if they would work in Tiger/if I could make it work, and the answer is yes I can

(I had been curious on this front since the iMac7,1 shipped with tiger and used ATI Graphics cards of the same generation, and the ATI Radeon 2600 XT's device ID was in those tiger drivers, so was quite curious to see what it would do!)
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started with a 10.4.10 iMac7,1 install DVD, installed that to an SSD via a VM, slotted it into my MP1,1 and it booted right up!, then installed the 10.4.11 (non Combo) update and it kept working
I will test in the coming days if it will work without the 10.4.10 iMac7,1 install DVD (but it is downloadable on the internet, its where I got my images from!)
with this working you could on say a MacPro3,1 or Xserve2,1 multiboot every intel version of OS X with graphics support on one mac! (although im not sure what the status on big sur is... , but you could do 10.4.11-10.15.6 for sure)
(sadly I dont have a MP3,1/XS2,1 so someone else can do that, can also be done a MBP4,1 or iMac7,1/8,1)