Is the iPhone Simulator actually as "slow" as device itself

Question

I wanted to know whether the iPhone Simulator in XCode "really" emulates the device hardware. So when deploying to iPhone 4s Simulator, will my app actually be "as slow as on a real iPhone 4S device" and when using an iPhone 6 Simulator, will it be as fast as on a real device?

Answer 1

The simulator does a really lousy job of indicating app performance. In fact it doesn't try.

For most things the simulator is much, much faster than an iOS device. It runs your code on an x86 processor, which is much faster than the ARM and has many times more memory. (It also actually links again OXS frameworks, not iOS frameworks. There is glue code in the simulator that makes it work with iOS code, but it's not perfect.)

However, some things, like Core Image filters and OpenGL graphics, are actually slower on the simulator than on a real iOS device.

The bottom line is that you can't really tell ANYTHING about your app's performance from the simulator, and shouldn't try. You can do basic development on the sim, but when it comes time to test performance, use real devices, and make sure to test on the oldest/slowest device your app supports (usually an iPhone 4s or iPad 2).

You also can't test memory usage on the simulator. A program that will run out of memory and crash on an iOS device may run just fine on the simulator.

Answer 2

The Simulator is a useful tool, and it should not be the only way you test an app. Because the Simulator is an app running on a Mac, it has access to the computer’s resources, including the CPU, memory, and network connection. All of these resources are likely to be faster than those found on a mobile device. As a result, the simulator is not an accurate test of an app’s performance, memory usage, and networking speed.

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