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Tahiti 7970 and GCN, functionality of global data share (GDS) and timers

Question asked by drallan on Feb 22, 2012
Latest reply on Feb 22, 2012 by drallan

After testing and porting a few kernels, GCN certainly lives up to expectations. Good work AMD.


However, there are two things I can't get to work. I'm using opencl but have an intermediate step that

can insert IL functionality, which in general works fine on the 7970.


However, on the 7970, the gds seems to function, i.e., all CUs can see what is written by other CUs,

*but* any data beyond offset 8 in the gds space comes back as zero. Below address 8 the data is

good. A VLIW card running the same code works properly. Is gds supported? does it use the same IL code

as before? How is gds declared in the header of the program, VLIW code uses (eg) dcl_gds_id(0) 4096.



The Tahiti compiler accepts the instruction  "mov r1.x Tmr.x" from the IL code but the code does nothing.

Again, is the timer functional on the 7970?


Any help is greatly appreciated.


Many thanks.