Finally seem to have got my rig stable after adding a 4th XFX 6600 (which bizzarely caused GPU1 to crash the rig every 24 hours for 10 days) 
I might wait for a few more days uptime then go back to the Asus 6600XTs and see if I can get a better hashrate/wattage out of them.
Hi @Batfink, thank you for your reply! I reset to your default values and try it for GPU6 w/o the SoC Freq.+VDD. Will report later… 
Thanks a lot!
Has anyone had random offline times here? No miner faults just a time period in where you 6600 rig just goes down? Trying to collect some data if you did.
which miner? use TRM and all will be fine or at least it will show the problem card.
My latest setup. Works 2-3 days without issues and reboots only because I still have to use WiFi (waiting for parts).
Anyone here doing dual mining on these cards? I haven’t had the balls yet to mess with my settings to get TON dialed in. Think the wattage would go up a lot.
Wow! I’m not alone. That’s good and bad news LOL. I was blaming the Wi-Fi but now we have LAN cable up and running so it’s not related.
So far: I did wipe out all the overclock and removed the flight sheet and re-do it again. I removed AutoFan and turned off Watchdog - the same issues randomly go “frozen”. Put them back since it’s not resolving my prob.
If you just plug in the screen it shows nothing. Just the last part where it got stuck. When you push the power button it does nothing (when it should shutdown). The only solution is to “hard-reboot” every day.
Need some help here! The worst part is it keeps draining electricity for nothing when it’s “frozen” and I’m not sure what to do next. It has two 850w EVGA PSU and chip to sync them but I don’t think this is the issue. IDK where to get any clues/logs of something to find out what’s the issue.
Hello I have a MSI Mech 6600 with Micron memory that is very frustrating to deal with. I’ve thrown all oc settings that I’ve seen in this post and nothing has worked Always get the GPU detected DEAD notification. Anyone have any tips or oc settings they can recommend?
I got one Card that will not run more than 6h under 700 VDD/Core Voltage.
With 700 VDD i made it to 3 days before errors occoure…
With micron memory? I’ll try it out soon as I’m home. 
Mine is hynix 
I messed them up - sorry
Darn
Well cant find more accurate OC for PowerColor 6600 rig now dualmining at decents speeds … still quite a little hot … will need extra airflow xD …
GPU 3 Still got serious TEMP issues must open it up to see …
I have the same expansion card, working very well but it seems the mainboard (Asrock h510 Pro BTC+) has sort of limitation at 12 GPUs, can’t even boot system with 12 connected (5 in the pci-e mainboard slots + 7 risers). Working very well with 11 GPUs, how many GPUs did you manage to use in a single system?
@Dojo76, Super stable (14 days uptime) at 13x GPUs (mix of 6600 and 6600XT) on a MSI B450-A Pro, problems with random 2-day crashes with 14x GPUs. I do have a ‘4x + 4x’ bifurcation card to replace the 6-port card in the 16x PCIe slot which might/should fix it but don’t have time to play with it at the moment. Its not always the same GPU that crashes which makes it very annoying to troubleshoot. Thankfully auto-reboot works 90% of the time so not too much downtime. Really need to resolve it soon 
What I would say from my experience so far using a 6-port PCIe Splitter/Packet Switch (AsMedia ASM1187e) in a 16x PCIe slot is all the GPU crashes are coming from GPUs connected to that card. I have increased voltages, etc but still the odd random crash for no perceivable reason. It could just be a slightly sensitive card, silicon lottery, blah, blah. Anyway, think I will swap it out for the bifurcation card with 2x 4-port PCIe Splitters/Packet Switches and see if it is stable. Not saying they are bad, just saying it seems difficult to get all six GPUs happy. It might just be my setup. No issues with the 4-port cards so far although the GPUs may need a bit more juice if they start crashing when connected to a splitter.
Update: Changed PCIe slot config from “Auto” to “Gen2”. Auto was working ok, the splitters seemed to auto-negotiate with the PCIe bus ok until the 14th GPU was added and then the random crashes after 24 hours started. Lets see if Gen2 helps…
