To the gamer, the main difference between Vulkan and OpenGL is that Vulkan should use fewer CPU resources to render the same workload. Also, Vulkan should be able to display more objects using the same hardware. Typically, games were limited by OpenGL (and DirectX up to 11) by the “number of draw calls” they could emit. Each draw call is a unique combination of geometry, shaders, and GPU state.
DirectX 12 is equivalent in performance and functionality to Vulkan and was launched before it. Vulkan is multi-platform, while DirectX 12 only runs on Windows.
That’s because older graphics APIs were originally built for old hardware (the 80s or 90s) and had been patched over time to accommodate programmable GPUs. Legacy OpenGL compatibility also meant that it was very hard to get off the old paradigm. Vulkan has been designed from the ground up for modern GPUs and multi-core CPUs.
Bethesda says that both AMD drivers and NVIDIA drivers will be supported. Regarding hardware, here are the official recommendations: “Vulkan is not currently supported on NVIDIA GPUs with 2 GB of RAM on Windows 7 or on the GTX 690. Users with these GPUs need to run DOOM on the OpenGL graphics API.”
Other than that, the minimum Doom PC specs remain exactly the same: Windows 7/8.1/10 (64-bit versions only), Intel Core i5-2400 or better / AMD FX-8320 or better, 8 GB RAM, NVIDIA GeForce GTX 670 (2GB) / AMD Radeon HD 7870 (2GB) or better, 55GB free HDD space, Steam account, Broadband internet connection. Check the Doom FAQ for more details.