A recent tear-down by iFixit however proves that the tablets do use a MT8135V SoC, although the memory interface is limited to a single channel 32-bit configuration compared to the dual channel configuration originally announced for the MT8135. As will be explained below, the use of the relatively expensive (because of a relatively large die area) and not very power-efficient MT8135 featuring Cortex-A15 cores and high-performance PowerVR GPU, a SoC originally announced for high-end tablets, in low budget devices like the new Kindle models does not make economical sense at all, especially from MediaTek' s standpoint, while MediaTek's existing MT8127 would have provided clear advantages for cost and power efficiency while still meeting performance goals.
Amazon targeting different segment of the market
The new tablet models are relatively small. The 6" Kindle Fire HD 6 is one of the few tablets of that size, while smartphones of a similar size (sometimes dubbed "phablets") are becoming more popular. Both tablet models do not have cellular connectivity and require a WiFi connection to connect to the internet. The tablets have a very robust design, being considerably thicker than most tablets. There are also versions with a software and accessory package specifically targeted at children.
Amazon uses a customized version of Android KitKat, without access to Google's Play Store and other Google applications, instead focusing on its own Amazon AppStore, with a somewhat different target demographic than higher-priced tablets.
MT8315 Amazon design win reported as early as August 2013, but use of MT8127 would be more economical
Already in August 2013, reports surfaced that Amazon would be using MediaTek's MT8135 in tablets to start shipping in 2014. Amazon has confirmed that a quad-core 1.5GHz MediaTek processor used in the new models. Current specifications mention to processor cores running up to 1.5 GHz and two cores up to 1.2 GHz. The MT8135 was announced more than a year ago as a relatively high-end chip and was originally expected to be commercially available much earlier. It was MediaTek's first chip using ARM's big.LITTLE architecture, using two Cortex-A15 cores clocked up to 1.7GHz and two Cortex-A7 cores.
The MT8127, announced this spring, is based on a proven and efficient quad-core Cortex-A7 CPU configuration and adds a relatively fast GPU (although limited to OpenGL ES 2.0 API support) and is listed with a maximum clock speed of 1.5GHz.
Power efficiency of big.LITTLE MT8135 likely to be problematic
ARM Cortex-A15 cores are notorious for high power consumption, and few Cortex-A15-based SoC designs have been commercially successful for mobile applications (especially smartphones), with problematic heat production and power drain often being reported. Cortex-A15 cores also take up considerably more die area than efficient cores like Cortex-A7 or Cortex-A53, resulting in larger, more costly chips.
Although power consumption and battery life of the Kindle tablets has not yet been tested, battery life specifications by Amazon are the same as for Kindle Fire HD models from previous years. Since the MT8135V is actually used in the new models, maintaining battery life is likely to be a challenge, while if Amazon had actually chosen the MT8127, the devices would most likely have provided much longer battery life.
The case against the use of the MT8135
Even though it has been established that the new Kindle tablets do use a version of the MT8135, several drawback are apparent. Although only two Cortex-A15 cores are used in the MT8135 instead of the four present in most existing big.LITTLE designs, a small form factor tablet would most likely not allow a large battery (the Kindle Fire HD 6 in fact has only a 3400 mAh battery, limited by the form factor) and power consumption could be problematic.
The relatively high performance PowerVR Series 6 GPU in the MT8135 should also contribute to high power consumption, for example when playing games, as well as being seemingly overpowered for the relatively low screen resolution since it is heavily oriented towards the use of dual-channel memory interface and a high display resolution.
On the positive side, MediaTek has experience balancing power consumption with its CorePilot technology (for example in octa-core CPUs), although this has not yet been proven for big.LITTLE CPU designs. MediaTek also originally announced its HMP (heterogeneous multi-processing) capability in conjunction with the MT8135, with all four cores being able to run concurrently.
In addition to the relatively large die area of the CPU and GPU (resulting in a relatively large, expensive chip), as well as increased manufacturing cost due handle potentially high heat production, a hypothetical design using the MT8135 would likely be using a relatively expensive dual-channel memory interface (matching the choice of CPU and GPU), further increasing cost at several levels. However, as it turns out the new Kindle tablets limit the memory interface to 32 bits in conjunction with the MT8135V SoC used.
Consistent with the cost characteristics of the chip platform, the MT8135 was originally announced as being targeted at the mid-to-high tier of the tablet OEM market. Clearly, this does not match the $99 price of the Kindle Fire HD 6, making the actual use of the MT8135 somewhat silly.
MediaTek already transitioning away from big.LITTLE
MediaTek has also announced a big.LITTLE smartphone platform, the MT6595 using four Cortex-A17 and four Cortex-A7 cores. However, although providing performance competitive with or surpassing current high-end platforms like Snapdragon 801, the MT6595 platform does not appear to have been widely adopted, which makes sense considering the relatively high power consumption of associated with the Cortex-A17 CPU cores and higher cost of the SoC, which make it stand out compared to other MediaTek SoCs, which tend to be low cost and power efficient.
In fact, MediaTek has already announced the MT6795, to be available this year not long after the MT6595, which does away with big.LITTLE and instead uses an efficient octa-core ARM Cortex-A53 configuration, with the other specifications being similar to the MT6595. This provides strong evidence that MediaTek is no longer focusing on big.LITTLE designs, including the MT8135, supporting the case that if MediaTek would make the decision, the new Amazon tablets in fact would not use the MT8135, but instead the newer, much more efficient MT8127.
Good game performance would have been achieved with MT8127 as well
Amazon has demonstrated relatively good performance of the new tablet models, for example when playing games, compared to competitive devices such as certain models from Samsung's Galaxy Tab 4 series. This is not unexpected, since the PowerVR Series 6 GPU in the MT8135 clearly provides high performance.
However, the Mali-450 GPU inside the MT8127 is actually a relatively recent GPU that is significantly faster than the Mali-400 commonly used in entry-level devices, and combined with the modest 1280x800 display resolution of the new Kindle tablets would have given respectable 3D game performance, not far from the performance of the actual MT8135V-equipped models. Although Mali-450 does not support the OpenGL ES 3.x API, OpenGL ES 2.0 continues to dominate, for which Mali-450 provides an efficient implementation (in terms of performance/Watt and performance/dollar).
The MT8127 is clearly a much more cost-effective (and more more power-efficient) chip. The MT8127 is likely to be dramatically more cost-effective than the MT8135, with much lower chip cost, much better battery life, and significantly lower manufacturing cost of the PCB and other manufacturing aspects, altogether a much better fit given the price segment of the new tablets.
Although the single-thread CPU performance of the quad-core Cortex-A7-based MT8127 is significantly lower than the Cortex-A15-based MT8135, this is not a critical issue in practice, and Android can already take significant advantage of multi-threading with a quad-core processor, mitigating the impact of single-thread performance bottlenecks.
Large-scale production of MT8135 does not make financial sense, unlike MT8127
Given the high manufacturing cost of the MT8135 (especially when compared to much more cost-effective tablet chips from MediaTek like the MT8127), it unlikely that MediaTek is making much of a profit on the chip even when selling millions of chips to Amazon.
In fact, because MediaTek is likely to be facing a critical shortage of wafer capacity at its foundry TSMC (being squeezed between juggernauts Apple and Qualcomm buying up capacity), the production of the MT8135, with its low profit margin, has probably cannibalized MediaTek profits as well as revenues, because, for example, for each MT8135 sold MediaTek would have been able to sell two or more much more cost-efficient and higher margin chips such as the MT8127 or MT6582.
Indeed, for this reason, the use of the MT8127 in inside the new Kindle tablets would have been much more logical. A prior commitment with Amazon for producing and shipping the MT8135, as reported previously in 2013, probably left MediaTek with no other options.
Few signs of financial gain from Amazon design win
As described in an earlier post, MediaTek's sequential revenue growth in Q3 is unlikely to be much greater than 10%, already low considering the normally expected seasonal increase expected in Q3. This provides additional evidence that MediaTek is severely affected by wafer shortages at TSMC, as well as the late introduction of smartphones SoCs with integrated 4G LTE baseband, and general price pressure on its chips. Despite probably shipping millions of MT8135V chips to Amazon, this probably has had the effect of limiting shipment of other, higher-margin MediaTek chips to other customers, because of an inability to fulfill demand. Indeed, tablets using more cost-effective MT8127 have been very slow to appear on the market, suggesting that MediaTek has been prioritizing tablet processor production of the MT8135V for Amazon because of capacity constraints. So while MediaTek has gained prestige from this design win, the financial gain is likely to be limited or even negative.
Strong prospects for new products, clouded by capacity concerns
Although the performance of MediaTek's upcoming Cortex-A53-based smartphone SoCs is likely to very competitive and they have been reported to to have gained widespread adoption in China for new designs, while also contributing to MediaTek's increasing competitiveness in high-performance segments, recent reports suggest competition for wafer capacity at TSMC will continue to be intense, bringing into question MediaTek's ability to translate any product strength (ranging from new and existing smartphone platforms to tablet chips like the MT8127) into actual sales and profit growth in the near term. If MediaTek continues to be obligated to produce the MT8135V in high volume for Amazon, that will most likely continue to negatively affect MediaTek's sales and profits.
Sources: CNET (Kindle Fire HD 6 and 7 announcement), DigiTimes (2013 MediaTek Amazon Kindle article), MediaTek (MT8127 announcement press release), iFixit tear-down article
Updated October 24, 2014 (Update to reflect the fact that the tablets actually do use the MT8135V SoC).
Updated November 2, 2014.