Scrypt-Jane can be a lot of 'fun'.
I have 8 identical MSI R9-270's between 3 systems (4,2,2) and each system requires quite different miner values to run stable and maximize hash without HW error....no easy copy paste, each require testing. I still haven't got the 3rd system with just 2 cards running stable....keeps rebooting every 10min-1hour. Seems there must be more interaction with the rest of the computer hardware than with Scrypt.
System1(4x R9-270) Avg78khash/s - I12 TC 16384 g1 w256 mem1200 engine1100 (last N was I16 TC11263 1250 1125 190khash/s)
System2(Main Desktop - 2x R9-270) Avg75khash/s - I12 TC17408 g1 w256 mem1100 engine 1100 (last N was I17 TC11263 1200 1125 185khash/s)
If I use System1 settings on System2 -> HW errors and eventual SICK gpus. if I uses System2 settings on System1 instant system crash/freeze. System3 runs fine using System1 or System2 for a bit then just suddenly reboots not freeze so still tweaking. Weird. No issues with crash/freeze/reboots until this last N change.
I also have 1 system of 4x 7950. that one I just changed I16 ->I12 and its happy...but only making 78khash/s so not as efficient as the R9-270. they were making ~250khash previous N. Maybe needs adjusting of TC to get more hash?
this nfactor was the first I had to change settings at. my new bat for 3x Gigabyte windforce 270x and 1x xfx dual dissipation 270 is now: --scrypt --Nfmin 4 --Nfmax 30 --StartT 1389028879 --queue 0 --scan-time 2 --expiry 4 --no-submit-stale -w 256 --gpu-memclock 1500,1500,1500,1400 --gpu-engine 1100,1100,1100,1100 -g 1 -I 16,16,16,16 --thread-concurrency 21568,21568,21568,21568 --temp-cutoff 90 --auto-gpu
this time around I had to change gpu engines down 15mhz but only on the 3x gigabyte 270x's. Im not sure if that did it, but I also changed my TC on the 3x 270x from 16000 to 21568. ended up being able to leave my -I the same and has been very stable. ( the xfx card is not NEARLY as stable as the gigabyte. im using one in my gaming pc atm also and mine on the side w/it till I get Linux, but it crashdumps and has driver has stopped responding errors all the time! the gigabyte 270x and my GeForce 480 gtx NEVER have had an issue. Ever. Running 4 clients of MMOs and music, + more abuse. Hell I could PLAY Aion on -i12-14 ,no lag, and still get half hash power! cant even load client now with xfx 270 while mining) hash rates are for the moment at around 92,92,92,91. I could get them higher but whats 20 kh total if your pc crashes every couple hours. more tweaking to do I suppose