AMD 6600 XT just came up right now so most probably Phoenix miner which has an history full of issues for the Big Navi 6000 series it appears to have the same problem.I have been suffering big time with Rx 6800 XT until the latest release 5.7b which I have a record it running for 75 hours without problems so far.I am pretty sure based on this that in future versions the 6600 XT will be fully supported without problems in Phoenix miner.
https://i.ibb.co/KWV1cjr/Phoneix-miner-75-hour.pngThanks to your advice (on an earlier post/page) of using a higher -eres number (-eres 8 is what I use), my rig has been able to run 70 hours non-stop without a crash. This is on 5.7b and the August AMD driver.
There is 1 problematic card which starts to drop shares on the 60th hour or so (Gigabyte) so I typically will need to do a reboot after 2 days, which is better than before where everything crashes in a day and a half, sometimes in less than a day.
On this rig there are 7 GPU's (all RX 6800). I am now considering adding more as RX 6800s are cheaper in my city than 3070's, have a lower temp + lower power consumption (thanks to MorePowerTool), and boosts to 70 Mhs from 62-64 MHs every now and then. The only drawback really is stability since max performance and efficiency for the 6000-series can only be had in Windows atm.