Also wondering on what mobo setup is gettin people 8-12 6600 XTs on one system.
I have a biostar BT250 btc pro board for 12 GPUs and I can only get four 6600 XTs to work. When I add a 5th they all turn to “Navi 23”. I’ve been doing countless reflashes, bios swaps, and swapping out risers and cables, everything I can think of and has been suggested for five days now.
I can load up the rest of the rig with GTX cards and it all works fine but one more 6600 XT turns all the 6600s into “Navi 23” and don’t work properly.
Hello, I post this here if it can help people.
6 GPU rx 6600 xt rig, this OC is ideal because the cards are very stable.
Core clock : 965
Memory clock : 1140
Fan : 40% or 50% as you want
Dude you can reduce the watts of your cards further. just look up for the values. remove the DPM state you use and input core voltage memory voltage and memory controller voltages.
keep your core clock and memory clock settings as they work nice for you.
why dont you put core Voltage VDD 636 and see what happens ?
Thank you @rhulov !
Now I got 52W to 55W with the same settings and the VDD at 636.
Hi darumix, can you please make a print screen? 
To show us the result :).
Ben.
if you like you can test even lower like 630 but if it dies , than you need to revert it back to 636. its a matter of testing and checking the results if it dies or makes rejected shares.
I tried this configuration but after 2 hours, the rig crash and reboot.
Yet I obtained 33 MHz for 50 W !
Too bad 
After a few hours of mining with these new OC settings, my GPU 5 crashed and displayed the error message “GPU driver error, no time” so I set all my gpu with the VDD to 630 except GPU 5 and since all works well. My 6-card rig has been very stable for 24 hours with these OCs. If you know how to fix the problem I had with GPU 5 that would be great. Thank you.
If it dies you cant lower it more than this. But you can put 636 or 640 as voltage.
When I put 640, or 636 or 630 VDD on my GPU 5 it crash.
go 1135 on memory and see what that gives you.
try 700 for vdd, lower by 5 every few hours until crashes, then go back up.
Powercolor RX 6600 XT 8 GB Red Devil | 0.6-210@210918 | TeamRedMiner v0.8.5
Running for 12hrs+ with no rejected shares.
Very power efficient config if your card is stable at these settings.
(thanks to rkulov for the VDD 636 setting suggestion)
Lower the Memory clock in increments if it hangs.
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Thank you for sharing. I just changed the VDD to 640, on my 2 rigs (19 X Rx6600 XT sapphire). And I consume 104 less (without loss of performance), (vdd at 600 previously).
these cards can be further tweaked if you know the correct values to set the memory voltage and memory controller voltage.
I imagine. But I don’t know how to do it. The base, maximum, etc. 
probably you did, but lets give it a try…did you enabled csm support in your bios ? helped me on my asus b250 mining expert
my 2 x red devil’s are maxed out on 32 mh/s on Team red miner, tried a lot of different settings, sometimes they jump to 33mh
Hi There,
have a new Sapphire 6600XT that causes havoc on HiveOS 0.6-210@210920. Running a H110 Pro BTC+ ASRock mobo, driver version 20.40 (5.11.0701).
The mobo recognizes the card fine, but upon hiveos boot I get the following error:
amdgpu failed to init sos firmware
Then it all turns to crap. Tried riser swaps, slot swap, putting the card in a full pcie slot. Nothing helps. Below is a screenshot of error.
Tried reverting all the way back to 0.6-207 and no difference in result.
Nice, thx - works on 2 of my 3 cards. 3rd drops zu 28 mh and i think it would go lower if i let 