// 3. Reserve GPU memory ranges (but no allocation yet) Mem_ReserveGPUBuffer(256 * 1024 * 1024);

Example from decompiled BO2 strings:

void PreGfx_Init()

// Shut down pre-GFX sound stubs Snd_ShutdownPreGfx(); // Create renderer device R_Init(g_hWnd, g_videoMemoryMB, g_backbufferWidth, g_backbufferHeight);