Demon's Souls - Required PC Specs?

[ScottyDoesKnow]

I booted up Demon's Souls and I'm only getting about 15 FPS once the game starts.

Windows 10 Pro
i5-2500k, quad core at 3.6GHz
16GB RAM
AMD R9 390

In Core Settings I have PPU set to Interpreter (fast), SPU set to Recompiler (ASMJIT) and Library Loading Mode set to liblv2 only

In Graphics Settings I have OpenGL, 16x9, 1280x720, Frame Limit off, D3D adapter set to the R9 390 and Write Color Buffers turned on (for the black screen issue, though the FPS is 15 with or without this).

Do I not have a good enough PC to run this or is it something else?