Ok, got some interesting news here:
Got the following config here:
• ASUS Maximus Extreme VIII Motherboard
• Sapphire RX480 Nitro 8GB in PCIe Slot#1
• Sapphire RX460 Nitro 4GB in AKiTiO Node Thunderbolt3 encloser connected to Gigabyte Alpine Ridge TB3 card in PCIe slot#3
• SIERRA 10.12.5 beta 1 (rev. 16F43c)
• CLOVER latest Rev. 4047
• CSM disabled in BIOS
• set PEG as primary GFX (thats the RX480 in PCIe slot#1)
• patched only AMD9500Controller.kext to recognize Device-ID 0x67DF1002
• NOT patched AMDRadeonX4100.kext with Device-ID 0x67DF1002
• patched some of the AMD-related kext with the following entry: IOPCITunnelCompatible = true
• NOT patched AMDRadeonX4100 to get 36 CUs for the RX460
booted the system via CLOVER right into desktop. Now take a look at System Information entries for both cards:
RX480 first:
as you can see: NO Metal support. Now lets see the RX460:
Yes, it is true: this card HAS Metal support !
Ok, so now see the entries for both cards from IORegExplorer - again RX480 (in slot#1) first:
NO accelleration for this card, cause we don't have any AMDRadeonX4100 entries. Let's go for the RX460 (via TB3 NODE):
Again: full support as you can see, we HAVE entries for AMDRadeonX4100.
And: i could run any benchmarktool like HEAVEN or LuxMark with full speed on all 4 connected monitors !
But there is one thing to mention: if i patch AMDRadeonX4100.kext to recognize 0x67DF1002 (RX480 device id),
i got stuck on boot just before comming to the desktop with same effect, as running one of the RX cards w/o any helper card.
Sorry guys... but i will try hard to found out, what causes the problem.
And evan that there are no AMDRadeonX4100 entries for the RX480 card, i still believe it runs as if there where, because that kext is fully loaded and activated for the RX460 <--- but i wouldn't bet my hands for it.
PS: forget to mention that i get BERBICE for the RX480, but AMDRadeonFramebuffer for the RX460 - but this is ok, cause both cards use different Connector patches - which could be made possible by CLOVERs "Arbitrary"-function, which i will try later this weekend.
PPS: full 8-channel HDMI audio output support on the RX480 (cause of correct patched DSDT and CSM disabled in BIOS):