It isn't surprising you get a boot loop when using two different shikigva boot-args since that is not how it works. The value of shikigva is a sum and the result by adding parameters which each have a different value.
To clarify: Originally, @h9826790 had found 96 (32+64) to be a good choice for the cMP. With WEG 1.3.5, I tried 112 (16+32+64) and 240 (16+32+64+128), both causing a boot loop. It turns out that the presence of 32 with 16 causes the issue.
Another thing to test. Does adding -wegtree boot-arg trigger proper device renaming for your Mac Pros? GPU should be called GFX0 in IOReg if it does.
Indeed, it does:
Code:
...
+-o IOU0@3 <class IOPCIDevice, id 0x1000001cb, registered, matched, active, busy 0 (960 ms), retain 12>
| | | +-o IOPP <class IOPCI2PCIBridge, id 0x100000219, registered, matched, active, busy 0 (959 ms), retain 10>
| | | +-o GFX0@0 <class IOPCIDevice, id 0x1000001cc, registered, matched, active, busy 0 (956 ms), retain 32>
| | | | +-o AMDSupport <class AMDSupport, id 0x100000412, registered, matched, active, busy 0 (0 ms), retain 5>
...