Admittedly I don't know the algorithms well enough to name a specific handicap. But perhaps there's a specific instruction or two that's really only used by cryptocurrency mining; a bit rotate or such?
What little I've skimmed about GPU mining is that it relies heavily on generating cryptographic hashes of a data set purposefully sized to blow out on-die storage while being modest enough to fit in on-board memory. The overall scheme is apparently designed to exceed what an FPGA or ASIC can keep on-die, while not being scalable to large amounts of parallel compute resources not tied to a common memory and its bandwidth, to help limit what a large cluster might do.
Ethereum seems to use a hash in the family of SHA3, which has a lot of iterative XORs and integer math applied repeatedly to a region of data.
Individual instructions may not really stand out, other than the workload not using FP or any graphics functionality--although simple checks on those items could be readily gamed or have false positives on non-mining workloads or portions of them.
The context of the workflow, which I think is a lot of iterative integer and logic math pulling in streams of memory and iteratively overwriting sections of storage might stand out. It might take something like static analysis of the program or identification of specific programs, the latter check being trivial to defeat and the former probably unlikely to withstand the monetary motivation to defeat it unless the whole GPU and software system were locked down.
I am not sure if there aren't some functions (noise functions?) with iterative math that might yield false positives as well.
The GPU front ends would presently not have much visibility to monitor the behavior of the wavefronts being launched, so their ability to throttle wavefront launches based on the presence of mining-type wavefronts would be low. Their general programmability and microcode store might let them host some more advanced heuristics, if access to such data became available.
The CUs would have more dynamic information, perhaps a flood of XOR operations and shifts in the instruction stream and a distinctive pattern of memory accesses. Perhaps instruction issue could throttle if a count of the various operations or events was accumulated over a time window, but that might be a level of context and tracking the streamlined hardware does not maintain.
Perhaps a more sure way to encourage a mining SKU would be to purposefully double down, and implement something akin to the SHA extensions in x86 for the GPU, and have that subject to SKU-specific throttling like DP. If used in a security context, cryptographic functions often purposefully stall to keep execution times flat and avoid side-channel leaks--which a mining SKU could dispense with.
Getting the level of specificity to the workload given its propensity to not use standards, or to change what it uses if the overall situation is "unfair" (why cryptocurrencies spawned from Bitcoin after ASICs took over, tweaked currencies having low cost to launch) makes implementing higher-level primitives in hardware such as this an uncertain affair.
That's a really good point. I didn't realize NV cards were that close on this generation.
Though the irony is that NVIDIA is probably better suited to handling this anyhow; besides a much larger volume to start with, they have a lot more experience enforcing market segmentation. Which I suppose puts AMD in a no-win scenario...
It seems to me that an issue AMD is facing is that GPU mining specifically targets a rather specific and yet non-differentiating element of GPU architecture that doesn't provide much of a knob or lever that makes it compelling in the other markets that more reliably set GPU prices or create long-term buy-in (professional applications, virtualization, games, machine learning, HPC, rich media, driver support, APIs, blue-sky research, devrel etc.).
Having higher than average local bandwidth and generic operation bandwidth in the design space of a consumer GPU is something that is overly fungible, and emphasizing that in excess of its general utilization of those other elements that make up the general utility/value-add is actually reminiscent of GCN.
I don't have much faith in mining yielding dividends for AMD. Block chains and distributed ledgers used by cryptocurrencies are finding use or will soon for monetary or business transactions, but I don't know enough about the space to know what GPUs offer if the mining component is dispensed with.