It's strange... But on my Pitcairn card 270X 4Gb miner can't use more than 3.5Gb of vmemory... 1 thread 1856 and 2nd 1644 (multihash 464 and 416 or 448+432) = 3500Mb. Increasig any thread without lowering other leads to OpenCL error on creating buffer for 2nd thread...
Add this line to the bat file "setx GPU_FORCE_64BIT_PTR 100". Will be used 4gb. Multihash 464 1 and 2 thread. R9 370 4gb 1150/1500 Samsung 575 h, timings (straps) from 1250.
As I know right variable set is "setx GPU_FORCE_64BIT_PTR 1" not 100. I tried it. Not helps. Miner show that card have 4096Mb memory, but can't use it all...
Give all bat file, please, I'll try. And config.txt
P.S. I forgot to point that it's on heavy algo. On v7 and v8 multihash is up to 832 both threads... Also about 3,5Gb... More gives error...