CODEWITHSUNDEEP
performanceassemblyx86hardware
phausy
phausy

Reputation: 25

how proprietary programs distributed as binaries do exploit the specificities of hardware they run on?

I always wondered how, when you buy a video game designed for x86 architecture (for exemple), this video game behaves often better with better CPU/GPU...

As far as I understand, there is no compilation during the installation process, so the instructions in the binary should be exactly the same whatever the hardware is. Therefore even if a CPU/GPU can handle a larger set of specialized instructions, these could not be in the program, because it would make the program incompatible with other hardware.

Am I wrong on this reasoning ?

How proprietary programs distributed as binaries do exploit the specificities of hardware they run on ?

Upvotes: 0

Views: 86

Answers (2)

Ross Ridge
Ross Ridge

Reputation: 39621

GPUs actually have widely incompatible instruction sets that no game actually ships with precompiled shaders (programs that run on the GPU). Not only do AMD's, Nvidia's and Intel's GPUs have different instruction sets, they completely redesign them for every new generation of chips. Instead games ship with partially compiled bytecode shaders, or in some cases plain source code, that are compiled at runtime by the video driver into whatever instruction set the GPU actually uses.

Upvotes: 1

zx485
zx485

Reputation: 29042

They detect the hardware capabilities at runtime(running at the target PC). The CPU features are usually detected with the CPUID-instruction at machine code level (see a raw overview here). This instruction is generally accessed via built-in compiler-intrinsics, e.g. __builtin_cpu_supports("sse3") for GCC (see Intrinsics for CPUID like informations as an example).

The GPU's capabiliites are also detected at runtime, often with the appropriate DirectX/OpenGL-APIs offered by the driver. For example, DirectX can fill a Caps Structure (Microsoft.DirectX.Direct3D) with some relevant information. Another possibility may be the usage of a database containing the capabilities of each graphics card (see DirectX capabilities on different graphics cards).

Therefore even if a CPU/GPU can handle a larger set of specialized instructions, these could not be in the program, because it would make the program incompatible with other hardware.

That's not the case. Newer instructions not supported by older hardware can surely be encoded in the executable. This will do no harm and will not crash the program as long as they won't be executed(run). Hence the CPU-Feature detection at runtime - the program will choose based on these features which code can be executed safely. Those other instructions will simply be treated like any other non-executable data - like pictures or text.

How proprietary programs distributed as binaries do exploit the specificities of hardware they run on ?

They do this by encoding the same functionality several times, each version optimized for a specific set of features/capabilities. Then, at runtime, the fastest possible version is chosen for execution and the others are ignored.

Upvotes: 3

Related Questions