I am using the simulator and it is showing 80% CPU usage, with just one image being displayed on the screen.
Here is the code:
SPRenderTexture *renderTexture = [[SPRenderTexture alloc] initWithWidth:width height:height];
// load an arbitrary image
SPImage *image = [SPImage imageWithContentsOfFile:@"ent-bg.jpg"];// row 1
[renderTexture draw:image];image.x += image.width;
[renderTexture draw:image];// row 2
image.y = image.height;
[renderTexture draw:image];image.x = 0;
[renderTexture draw:image];// row 3
image.y = 2 * image.height;
[renderTexture draw:image];image.x += image.width;
[renderTexture draw:image];// display the rendered texture in an image
SPImage *renderImage = [SPImage imageWithTexture:renderTexture];
[self addChild:renderImage];[renderTexture release];