Authors: Timothée Pineau and Pieter-Jan Plaisier

50% extra performance. Just on air cooling – no LN2 required. Yes, ambient cooling is all it takes to significantly increase the performance of AMD’s new APU codenamed Kaveri. To make things short, what makes the Kaveri so interesting is the HSA technology. HSA allows both CPU and GPU to read from the same memory registry, without having to reserve it for one specific purpose. In previous APU generations we already noticed how important system memory overclocking is for the 3D performance of the APU. Although AMD did not really highlight overclocking as one of the major selling points of the Kaveri APU, we are convinced the performance increase gained through overclocking is very significant.

It brings us back to the early days of overclocking, where a fiddling in the BIOS resulted in great and free performance.

50% Increase, Hooray!

Without too much hassle, we achieved a performance increase of 50% when testing the AMD Kaveri in our Taipei labs. Using 3DMark Fire Strike to measure the performance, only a few BIOS adjustments are necessary to achieve this. Oh, right! The most important thing: you just need a simple air cooler!



Before and after overclocking

Test system: AMD Kaveri A10-7850K, Gigabyte A88XN-WiFi, Vengeance 2666C10 Samsung

System Memory – The Key to Success

Memory frequency and therefore memory overclocking is the key to success when trying to extract more performance from the Kaveri APU. As Corsair illustrates on their blog, historically speaking the APU has always been limited by the system memory bandwidth. Although this is also noticeable when using the CPU cores, this becomes painfully clear when using the internal graphics processor. It’s simple: every single MHz counts for 3D performance.

The Kaveri APU uses a Hawai GPU architecture in their Radeon R7 grade integrated graphics processor. On normal discrete graphics cards this architecture makes use of the bandwidth provided by the GDDR5 memory. But on an APU system, the GPU only has the DDR3 system memory available. And that’s where the bottleneck lies. For example by upgrading from DDR3-1600 to DDR3-2400 memory (the highest available memory ratio for Kaveri) you can easily achieve a 20% performance increase. And not only in synthetic tests such as 3DMark, but also in real games like BioShock Infinite or Grid2. It is interesting that the performance gain is actually more noticeable in game benchmarks than in the synthetic ones. Anyway, all this performance gain is without even starting to overclock. With a bit of overclocking know-how and the right memory kit you can easily get that same 20% performance boost. And, hey, isn’t that how we all got started in the first place?!

Just before we published this article, we saw that Corsair published another Kaveri scaling article. Although their conclusion is that DDR3-2133 is the sweet spot for Kaveri, we would argue that going up even higher than DDR3-2400 still results in higher performance gains. For example, going from DDR3-2400 to DDR3-2640 resulted in an average FPS increase of roughly 5%! Keep ‘clocking up is our advice!

AMD on Kaveri Overclocking

In January we attended a technical press meeting with AMD in Taipei. In the presentation slides, AMD already highlighted the overclocking capabilities of the new APU. Enthusiasts like you, me, and everyone else here at HWBOT, are often cautious when confronted with this type of marketing information. But this time around, there was no reason to be suspicious. In fact, it seems that AMD might have been underselling the overclocking aspect of Kaveri. The 50% performance statement would have been a great selling point and as our tests show, isn’t an unreasonable claim. Perhaps the reason of the less attention for overclocking is due to the underwhelming capabilities under extreme overclocking – something AMD has been talking about in the past recent years.

So what’s going on? Well, simply put “they ain’t ‘clocking so well”. According to internal testing, the new Steamroller architecture can reach not more than 7GHz under extreme cooling. To compare, with the previous generation APU – Richland – 8.5 GHz was reached. Why the overclocking results are so poor is a good question. After asking around, it seems like the finger is pointed mostly in the direction of the new 28nm production process. In case you don’t know, the production process of the 28nm Steamroller CPU core and the 28nm Hawai GPU core are vastly different. Combining two different 28nm silicon on one die is not a simple task. Rumors go a new and improved process might increase the overclocking capabilities of the Kaveri APU. Today, the CPU-Z frequency record on Kaveri is of 5812 MHz. This is still quite far from the 7 GHz claimed and even further from the frequency world record of 8709 MHz (with FX-8150).

Conclusion: practical overclocking is back!

Sometimes we forget that most of the overclockers don’t hunt for records, but are simply looking for something extra for their daily driver. Overclocking is not just about the records. In the beginning, overclocking was just about getting a free performance boost. In that respect, Kaveri is an interesting new hardware item. Considering factors like performance gain, the ease at which it can be done and the simple cooling requirements, the Kaveri is actually a great APU for overclocking. It gives us what we want, free performance, and it reminds us of the good old days. Kaveri, hooray!