The global_work_offset value you pass to clEnqueueNDRangeKernel is used as the starting value for get_global_id(0). If global_work_offset would be 10 and we had 5 work-items, the nonces generated would be 20, 21, 22, 23, 24, 25, 26, 27, 28 and 29 so we loose nonces from 10 to 19 and use ones, that should not be base ... would that create duplicate work? You pass -D GOFFSET to the kernel, right?
That would prove true for a base of (2147483647 - global worksize) because doubled it's over 2^32. How big are the nonce bases and what would be the global worksize for -I == 14 (as this is the maximum)?
Dia
global worksize = 2^(15 + intensity) so it's 29 max and it's double that for 2 vectors and so on...
cgminer always tries to test the entire range of nonces up to 2^32 so it will *always* get to a value above 2^31 where it will wrap with a doubling of the global id regardless of what intensity it's at.