Diakgcn should be using the modified PreVal4 which includes T1.
diff --git a/device-gpu.c b/device-gpu.c
index e39bff4..f7cbcc2 100644
--- a/device-gpu.c
+++ b/device-gpu.c
@@ -769,7 +769,7 @@ static cl_int queue_diakgcn_kernel(_clState *clState, dev_blk_ctx *blk)
nonces[i] = blk->nonce + i;
CL_SET_VARG(vwidth, nonces);
- CL_SET_BLKARG(PreVal4);
+ CL_SET_BLKARG(PreVal4_2);
CL_SET_BLKARG(cty_h);
CL_SET_BLKARG(cty_d);
CL_SET_BLKARG(PreVal0);