Before I knew about cryptocoins, I ran a lot of GPU's for BOINC distrubuted computing projects. There are/were(?) heaps of CPU based Prime number finding projects but none of them ever used GPU, so I am agreeing that branching is not suitable for the hardware and that is why no one ever bothered to make a program to mine on them. For this reason I suspect we might never see a GPU or ASIC prime number miner.
So you doubt that mtrlt can do the trick? ->
https://bitcointalk.org/index.php?topic=258540.0And another step into the direction GPU miner was taken here:
https://bitcointalk.org/index.php?topic=258982.0There might be no GPU miners atm, but I doubt it will take long. Primecoin is suprisingly attractive. Even a pool is available although it had to be built almost from the scratch due to the completely new Proof-of-Work approach.
I suggest we'll have a GPU miner that outperfporms the current CPU miners for Primecoin (and that is more energy efficient) before we have FPGAs for Litecoin (that are more energy efficient than GPU miners)
