Power Draw: Efficiency
Next, we’ll use the A10-7700K and -7850K's unlocked multiplier to approximate the performance level or power draw of the A10-7800, one at a time.
Overclocking AMD's A10-7700K To Approximate An A10-7800's Speed
We put the lower-end APU into overdrive by overclocking its host and graphics processing blocks, simultaneously increasing the TDP ceiling to achieve similar performance in our three benchmarked games. But while we can get power consumption to rise, the -7700K just can't match the -7800's frame rates. One explanation is that we had to boost the x86 cores to 4.2 GHz to compensate for the pruned GPU, but we couldn't overclock the graphics engine enough to make up for the missing shaders.
|Minimum||Maximum||Average A10-7700K Overclock||Average A10-7800|
|CPU +12 V||16.8 W||64.8 W||39.6 W||32.0 W|
|Motherboard +12V||0.0 W||19.2 W||8.2 W||7.1 W|
|Motherboard +3.3 V||0.3 W||0.4 W||0.4 W||0.1 W|
|Motherboard +5 V||0.5 W||2.3 W||1.4 W||1.1 W|
|System Total||23.1 W||76.3 W||49.6 W||40.3 W|
Apart from the fact that we couldn’t match the A10-7800’s performance level, power draw increased by a whopping 9 W (or 24%).
Underclocking The A10-7850K To Approximate The A10-7800
Now we're reducing the A10-7850K's clock rate to match the -7800, and in a second test adjusting the TDP target to match the -7800’s power consumption.
It turns out that the A10-7850K is 2-5% faster during gaming. Similarly, its CPU performance is up to 5% higher. However, power draw is up to 29% higher! This is proof that the A10-7850K was tuned more for performance than efficiency. AMD wanted to put its best foot forward in the benchmarks, and as as a result the -7850K operates beyond Kaveri's sweet spot at the expense of efficiency.
|Minimum||Maximum||Average A10-7850K||Average A10-7800|
|CPU +12 V||7.2 W||69.6 W||41.3 W||32.0 W|
|Motherboard +12 V||0.0 W||19.2 W||8.1 W||7.1 W|
|Motherboard +3.3 V||0.3 W||0.5 W||0.4 W||0.1 W|
|Motherboard +5 V||0.5 W||2.3 W||1.5 W||1.1 W|
|System Total||18.1 W||81.3 W||51.3 W||40.3 W|
Comparison After Underclocking
When we underclock the A10-7850K to the -7800’s power level, we experience 1.5%-lower gaming performance. This is a small difference though, which could be the result of any number of variables.
What we really show is that the A10-7800 is basically a factory-underclocked A10-7850K and not a brand new APU. Besides lower stock clock rates, it lacks the -7850K’s unlocked multiplier.
|Minimum||Maximum||Average A10-7850K @ A10-7800||Average A10 7800|
|CPU 12V.||12.6 W||58.0 W||32.2 W||32.0 W|
|Motherboard +12 V||0.0 W||21.6 W||7.4 W||7.1 W|
|Motherboard +3.3 V||0.0 W||0.2 W||0.1 W||0.1 W|
|Motherboard +5 V||0.1 W||1.9 W||1.1 W||1.1 W|
|System Total||13.0 W||76.1 W||40.7 W||40.3 W|
AMD positions its A10-7800 perfectly, hitting the right balance between power and performance for Kaveri. The chip's default frequencies constitute the best compromise between performance and power consumption. The -7850K's disadvantage against the -7800 comes from the x86 cores, which are more efficient at the -7800's lower clock rate, while not limiting the APU's graphics component.