scrypt is sequential memory-hard algorithm and is dependent (mostly) on memory access speed. Since memory requirements are enormous (16MB per single scrypt operation by default) and since access pattern is random, CPU caches would not help a lot. It does help much more with bcrypt though where the state is just 4KB and can fit in L1 cache completely. scrypt is unimplementable on GPUs for other reasons, mostly that there is just not enough memory - assuming you can utilize ~2GB of videoram, that would feed 128 workitems or 2 wavefronts which is quite inadequate to keep even one of the CUs properly utilized and definitely not enough to hide any memory latency.
Wouldn't the same exact restrictions on GPU applies to KC then? In fact it would pretty much apply to all large parallel architectures.
You would likely benefit a _lot_ more if you can run several independent SHA256 operations on those X ALU units in parallel manner.
Just what do you think bitcoin mining is?
You clearly do not understand how computer architecture or dependency resolution works. Waiting on the results of a previous instruction? Just start work on a non-dependent instruction.
The current bitcoin mining hardware is restricted by the number of ALUs. True there might be a point where you need to increase the registers, decoders, scheduling to feed all those ALUs, but that's not until you increase the ALU resources drastically from where they are now.
Bitcoin mining is an
embarassingly parallel problem. There is basically NO work to be done to enable more parallelism besides throwing more ALUs at the problem.