AnandTech iPhone 4s Tests – What do they mean?

AnandTech ( is truly a professional blog with some of the best technical analysis you will find. They have just published a set of tests results on the iPhone 4s, titled:

iPhone 4S Preliminary Benchmarks: ~800MHz A5, Slightly Slower GPU than iPad 2, Still Very Fast 

I thought I would explain some of this to those with less technical backgrounds.

First, a few points:

  1. Apparently, these tests were not made by Anand Tech themselves, but gathered from other bloggers who seemed to have had early access to 4s units. Hence the “Preliminary” in the title. AnandTech will be running their own tests as soon as they get their own units.

Some Tech Basics

  1. CPU = Central Processing Unit: This is the “Brains” of a computer that reads instructions from programs, and makes everything happen in the computer. (Smartphones are miniature computers with phones incorporated.)
  2. GPU = Graphics Processing Unit: This is a special kind of processor, similar to a CPU, but designed to process image data. They are designed to perform certain mathematical operations repeatedly on millions of graphical data points. (They can also be used to process certain types of mathematical problems and are seeing new uses in this area.)

Click here for more Computer Basics Terms

One thing that is important to note is that the overall performance (speed) of a system is dependent on many things, and not simply the speed of the processor and/or the number of cores, nor on any other single factor. Additionally, the overall design of the system and subsystems may enhance certain aspects of performance will neglect other aspects. So one system may load and render multiple web pages very quickly, but be slower at certain types of graphics operations.

Finally – System performance is dependent on software as well as hardware. This applies both to the Operating System (OS) and to the particular application being run.

There are basically two types of tests. (Well I am sure you can come up with other classifications, but for our purpose this will do.) These are “real-life” tests which use real software programs, and benchmark tests which are programs designed specifically to test system performance. While the latter are more likely to test compare real limitations of a system (or some part thereof), they sometimes are not indicative of real user experience of said system. A mix of both types of tests is important to get a useful view of a system. I think one could say that benchmark tests test the hardware to the limits, while software tests give better overall system analysis. The problem with software tests is that you cannot test every aspect of even one piece of software, let alone of all software in its class.

Test Results:

Browser Tests

There were two browser benchmark tests with slightly different results. In both cases, the 4s handily beat all Android phones, pretty much tying the Galaxy Tab, which, of course, is a tablet not a phone. It should be noted here that the iPhone 4 (no ‘S’) was roughly comparable with the best Android phones when upgraded to iOS 5. So people who keep these phones should see a very significant browser improvement when they upgrade.

Graphics Tests

In the graphics tests listed, again, the 4s handily beat all Android phones, and  the Galaxy Tab as well.

A5 Clock Speed

It appears that the A5 chip in the iPhone 4s is clocked at 800MHz instead of 1GHz (1000MHz) as in the iPad. Now why would Apple want to “cripple” its CPU? Simple. Two reasons.

  1. In the fabrication of Integrated Circuit chips, each chip is tested after production. A percentage pass and a percentage fail. But some of the failures can still be used at reduced speed. Thus, lower speed means you get higher production from the fabs.
  2. More importantly, I am sure, is the reduction in electrical current consumption. As the report state:
    • Dropping a CPU’s core voltage, yields a greater-than-linear decrease in power consumption, making the marginal loss in clock speed a good choice.
What are the implications of this? Again as AT continues:
    • Apple does have to exploit its strengths in software to avoid any tangible performance penalties. Apple has traditionally done this very well in the past…

I would like to add, that this is not only software, but the A5 also has superiority over the competing Tegra 2 chip frequently used in Android phones, particularly in the GPU. Without getting too technical here, both system are based on the same design by the ARM group. The specifications for the dual-core ARM Cortex-A9  architecture allows for different GPUs, and Apple elected to implement a much faster GPU than is found in the Tegra 2. The results of tests bear this out.

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