It's easy to get good speeds with one card. The more cards you add, the more strange things happens. My GTX 1660 TI rigs have uptime of several weeks.. Early test of MorePowerTool did not help either.
Right? Especially for my XFX 570 Rigs. Half of them are Micron and the other half is Hynix.
One default setting is 1100/2000 where the other is 1180/1950. Exact same card just different memory.
As far as overclocking goes I have it set to:
-acm -wdog 1 -tt 70 -hstats 2 -powlim -5 -cvddc 900 -cclock 1100 -mvddc 900 -mclock 2010 -fanmin 25 -fanmax 90
and average 29MH/s each except for one which only gives me 26MH/s. It bugs the hell out of me!
If I change anything even a little everything goes crazy. I start getting incorrect shares, hardware errors, crashes and best case scenario it significant (at least 10%) drop in hash rate.
Example: If I set the mclock to 2000 (instead of 2010) I lose average 27.5MH/s across the board. Even the one that gives me 26MH/s when it's set to 2010. Doesn't make any sense.
I even try -mclock 2010,2010,2010,2010,2000,2010,2010,2010 (changing only the 5th card) and nothing happens. Like I said, it bugs the hell out of me.
My XFX 5700 rig of just 3 identical cards (so far) has a card that will not ever go beyond 1800Mhz. It just can't. The others will go up to 1820 but crash after a couple of hours (day max) 1810 is fairly stable but as soon as I move that card to even 1805 it'll start hashing 0MH/s within an hour. I'm always trying to optimize it though. But I've reflashed the bios, played around with drivers, used MorePowerTool, etc. It seems like there are a lot of people on here that have their own little "sweet spot" for the relatively same equipment and what works for one person doesn't always work for everyone else.