Technical Q&A QA1168

How do I determine how much VRAM is available on my video card?

Q: How do I determine how much VRAM is available on my video card?

A: The CGLQueryRendererInfo() and CGLDescribeRenderer() functions allow you to obtain the properties of the renderers on your system, including their VRAM sizes. On OS X 10.7 and later, you can query a renderer with the kCGLRPVideoMemoryMegabytes parameter to get the number of megabytes of video memory available to the renderer.

See CGL Reference Renderer Properties for the complete list of renderer property constants including kCGLRPVideoMemoryMegabytes, kCGLRPTextureMemoryMegabytes, etc.

Listing 1 demonstrates how to determine the VRAM size for your current OpenGL renderer.

Listing 1 Finding the current renderer's VRAM size

- (void)logVideoMemoryCurrentRenderer

    GLint virtualScreen = [[self openGLContext] currentVirtualScreen];

    // Since this may be called from outside the display loop, make sure

    // the context is current so the GL calls all work properly.

    [[self openGLContext] makeCurrentContext];

    // Use the current virtual screen index to interrogate the pixel format

    // for its display mask and renderer id.

    // Note, "pixelFormat" is the NSOpenGLPixelFormat that your OpenGL context

    // is created from, typically created in your OpenGL view's -initWithFrame:

    GLint displayMask;

    GLint rendererID;

    [pixelFormat getValues:&displayMask forAttribute:NSOpenGLPFAScreenMask forVirtualScreen:virtualScreen];

    [pixelFormat getValues:&rendererID  forAttribute:NSOpenGLPFARendererID forVirtualScreen:virtualScreen];

    // Get renderer info for all renderers that match the display mask.

    GLint i, nrend = 0;

    CGLRendererInfoObj rend;

    CGLQueryRendererInfo((GLuint)displayMask, &rend, &nrend);

    GLint videoMemory = 0;

    for (i = 0; i < nrend; i++)

        GLint thisRendererID;

        CGLDescribeRenderer(rend, i, kCGLRPRendererID, &thisRendererID);

        // See if this is the one we want

        if (thisRendererID == rendererID) {

            CGLDescribeRenderer(rend, i, kCGLRPVideoMemoryMegabytes, &videoMemory);

            NSLog(@"%@", [NSString stringWithCString:(const char *)glGetString(GL_RENDERER)

                                            encoding:NSASCIIStringEncoding]);

            NSLog(@"Renderer ID = 0x%x", thisRendererID);

            NSLog(@"Video Memory = %d MB", videoMemory);

    CGLDestroyRendererInfo(rend);

If you are looking for the VRAM sizes of all the renderers on your system, including those that are not attached to monitors (offline renderers), you may specify a -1/0xFFFFFFFF display mask in the CGLQueryRendererInfo() function. See Listing 2 for an example.

Listing 2 Finding all renderers' VRAM sizes

- (void)logVideoMemoryAllRenderers

    // Get renderer info for all renderers that match the display mask.

    GLint i, nrend = 0;

    CGLRendererInfoObj rend;

    // Using a -1/0xFFFFFFFF display mask enables us to find all renderers,

    // including those GPUs that are not attached to monitors, aka. offline renderers.

    const GLint displayMask = 0xFFFFFFFF;

    CGLQueryRendererInfo((GLuint)displayMask, &rend, &nrend);

    for(i = 0; i < nrend; i++)

        GLint thisRendererID;

        GLint videoMemory = 0;

        CGLDescribeRenderer(rend, i, kCGLRPRendererID, &thisRendererID);

        NSLog(@"Renderer ID = 0x%x", thisRendererID);

        CGLDescribeRenderer(rend, i, kCGLRPVideoMemoryMegabytes, &videoMemory);

        NSLog(@"Video Memory = %d MB", videoMemory);

    CGLDestroyRendererInfo(rend);

Document Revision History

Date	Notes
2014-03-11	Updated for OS X 10.9.
2004-10-11	New document that using CGLDescribeRenderer to find the physical size of VRAM on installed hardware.