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Dwelling into the ASUS Energy Processing Unit

Each AI Gear 3+ setting will result in the FSB (and multiplier) to be changed. Let’s walk through each setting throughly and take a look at what happens.

The first processor we tested with the ASUS EPU is the Intel Core 2 Duo E4500. It is a 2.2GHz part with a 800MHz system bus, and 2MB of L2 cache.

There are five modes to choose from in AI Gear 3+: maximum power saving, medium power saving, high performance mode (normal), turbo and auto.

We first proceed to test the maximum power saving mode.

We note that the FSB is reduced to 180MHz from the default 200MHz. The multiplier goes down from the default 11x to 6x. If one were to just enable C1E/EIST via the BIOS and not use AI Gear 3+, the multiplier will also drop to 6x on idle. A lesser Vcore is used to power the processor at this stage.


However, interestingly, on this mode, the multiplier is locked to 6x irregardless of the processor’s load level. As a result, the CPU only runs at 1080MHz on full load (180 x 6). Although this produces an impressive low power consumption on full processor loading (since processor speed and Vcore remain the same as idle), performance is effectively halved as we would see from the performance table shown later on in this article. 


The next mode is the medium power saving mode. The FSB is increased by 10MHz from the maximum power saving mode’s 180MHz. The multiplier value still remains at 6x on idle, although the Vcore is increased a little.


On load, the multiplier behaves ‘normally’ by kicking up to 11x, which is the processor’s default. On a system without AI Gear 3+ being in control, the multiplier will be 6x and 11x on idle and load respectively. Since the processor is now running at 2090MHz (190 x 11), a slightly higher Vcore is pumped in on load.


Maximum performance mode is reported as ‘Normal’ setting by AI Suite as well. The FSB runs at the processor’s rated speed, and the multiplier behaves the same way as a system with C1E/EIST enabled.


Basically running a system with the high performance mode, is the same as running the system without ASUS AI Suite installed.



Turbo mode exhibits the same behaviour as the maximum performance mode, but the FSB is overclocked to 210MHz. At maximum processor load, the processor runs at 2310MHz (210 x 11). This means the processor is actually running overclocked. I would probably call it a ‘mini-overclock’ mode since it forces a higher than default FSB speed, yet retains C1E/EIST power saving behaviour by kicking down the multiplier to 6x on idle and going back up to 11x on load. In the subsequent tests in the following page, the processors are also similarly overclocked at about 5% without any compromise to stability.


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