These are two settings I use for the R9 290 and working at n-factor of 11:
1st Computer with R9 290
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setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
yacminer -o x.x.x.x:20112 -u lumberinvestments -p qdwq2133s --scrypt --nfmin 4 --nfmax 30 --starttime 1387769316 --lookup-gap 2 --thread-concurrency 28600 -w 128 -R 6528 -g 1 --expiry 10 --gpu-engine 1070 --gpu-memclock 1500 --gpu-powertune 20,20 --auto-fan --scan-time 1
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Second computer with R9 290 GPU 0 and R9 270x with 4 gigs of memory as GPU 1
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setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
yacminer -o x.x.x.x:20112 -u lumberinvestments -p lsdq22oos --scrypt --nfmin 4 --nfmax 30 --starttime 1387769316 --lookup-gap 3,2 --thread-concurrency 42000,28600 -w 128 -R 9728,10240 -g 1 --auto-fan --scan-time 1 --expiry 10 --gpu-engine 1070 --gpu-powertune 20
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In this second computer I get almost 130 kh/sec with no HW for the R9 290 and almost 90 kh/sec for the 4 Gb R9 270x
You can see that the hashing speed differences between the cards start to get lower as the n-factor goes up.
In no way in windows you will be able to access all 4 Gb of the card, just download HWinfo and use it, look at the dedicated and dynamic memory of the videocard.
The higher the lookup-gap the higher thread concurrency you can go. Beware that there is a point when you increase the raw intensity and your hashrate will drop dramatically. That is the sweet spot. First you set up lookup-gap and thread concurrency until you can't go up anymore with thread concurrency. Have a low raw intensity. Then you increase it slowly and you will see your hashrate increasing, but stop when you will see the HW or sudden drop in hashrate.
Everything depends on your other configuration, like system RAM. If you have too little, you will not be able to go so high TC. I use 4 GB of system Ram and I assume I might be able to get higher if I put 8 GB total.
If this has been proven useful then you can donate to me some QQC and I will donate further share to Thirtybird
Here is my QQC address: QhACLXR1SbQu354aVJWf5EYYS8dPfFgVKN
We need to raise QQC to the sky by increasing the hashrate !
Have a nice day !