It is my understanding that it sits in between a GPU and a CPU in terms of "ideal work". Like a GPU it favours SIMD work, but it is better at dealing with branc

It is my understanding that it sits in between a GPU and a CPU in terms of "ideal work". Like a GPU it favours SIMD work, but it is better at dealing with branches and a lot of random memory accesses[1] (it still favours linear work of course). It also uses a more familiar architecture, leading Intel to claim it is easier to master than GPU-programing, but I personally disagree as x64 is already much more complex than GPUs. In terms of FLOPS the FX-9590 is still significantly slower. I don't know the exact numbers, but it will be hundreds of MegaFlops, whereas the Phi runs at ~1 TFlop. In part because the cores are basically low-end (in-order) atoms with modules bolted on for HPC (avx-512 instructions, instructions for exponentiation for example). Data transfer to the card is a lot slower than reading from ram, correct, but on the other hand once it is on the card it is a lot faster (wiki says the fastest Phi has 350 Gb/s, Corsair claims a maximum of 70 Gb/s for DDR4)[2]. So generally, as long as you have a decent ratio of work/memory access and your work is parallel you could use a Phi to speed things a long. You would want to use one in the same situations as were you'd want to use a GPU, and the Phi would be preferable if your computations and memory access patterns are nor perfectly homogeneous (e.g. branching which can't be rewritten), as this kills performance on GPUs. [1] I'm pretty sure Intel claimed this, and it makes sense when you think about it, but I can't seem to find a source: Could someone confirm this? [2] Do note that it 350Gb/s shared between the cores, not 350 Gb/s each.