Antonio Luca Alfeo

Maurizio Palmieri

ARM CORTEX

1. Snapdragon 810 (big.LITTLE)

2. Mediatek MT6752

3. Nvidia Tegra K1

4. HiSilicon Hi3798M V100

5. Mediatek MT8173 (big.LITTLE)

INTEL

1. Clover trail+

2. Bay trail

3. Moorefield

4. Cherry trail

High reliability (less than 10 fault per year).

Long time battery life (at least 1 day).

High computing performance (more than 2 GB Ram, 4

IPC,1.7Ghz ).

The Z35XX (Moorefield) family of Intel SoC offers fast and

smart performance and long battery life for Android

devices.

It is LTE optimized: supports Intel's XMM 7260 LTE silicon

which is CAT 6 capable.

Moorefield is based on the Silvermont CPU:

1. 64-bit microprocessor.

2. Out-of-order execution.

3. Back-end decodes and issues 2 instructions per cycle.

4. Dispatches 5 operations per cycle.

5. Consuming under 1W/core.

2 predictors:

1. BTB that provides low latency predictions over

instruction fetching.

2. Decode predictor controls the speculative

instructions issuing into the back-end and can

override earlier predictions.

A quad-core system with frequency from 1.8 up to 2.3

GHz(thanks to Intel SpeedStep technology)

24KB D-cache(6 ways) and 32KB I-cache(8 ways) for L1 caches.

2*1MB L2 cache(16 way) each shared by a couple of cores.

Up to 4GB of Main memory(2*LLDDR3) with a max bandwidth

of 12,8 Gbps.

A 533 MHz PowerVR G6430 GPU

The L2 is non-inclusive and non-exclusive relative to the

L1D and is a writeback design with full ECC protection

and pseudo-LRU replacement.

System agent allows reordering of memory requests

optimize for performance and quality of service.

Silvermont integrates Intel’s Core IDI, a lightweight point to

point interface.

This interface has independent read and write channels, and

it features high bandwidth and support for out-of-order

transactions.

In Silvermont, the IDI and CPU frequencies are largely

decoupled - enabling good bandwidth out of the cores even

at low frequency levels.

50% higher IPC for Silvermont

versus the previous generation.

Out-of-order scheduling provides 30% and perhaps 5-

10% for better branch

prediction.

The 22nm process technology

reduces Vmin by 100mV, and

increases clock frequencies by

20-30%.

Online intensive gaming (MMORPG for 4 hours)

Complex GPU processing (at least 60 fps)

High quality streaming video and audio (more than FHD

video)

High resolution screen

Tagliare l’immagine

Both chips are made on a 20nm process, big.LITTLEcortex A57 + A53, clocked at 2.5 GHz+.

Both have their LPDDR 4 memory clock speed at 1.6GHz, with peak memory bandwidth reaching up to 25.6GB/s.

Optimization procedure are different.

GPU: Tegra X1's GPU 256 unit at clock speed reaches a whirring 1GHz, while the Adreno 430 288 GPU cores purrs at 600MHz.

More (from 1 to 4, not

symmetric neither the

same) core clusters

switchable by

cpufreq driver to

balance

power/performances

ratio.

Very scalable

solution, 40

microsecond switch,

possible all cpu on.

Cache coherency tecnique:

1. Software: flush and invalidate.

2. Hardware: more efficient and simply done by AMBA 4 ACE

bus interface through L1 shared cache and L2 different (for

purpose) but visible cache.

A snoop filter reduce the snooping traffic. When replacement

of one of the entries is required, the snoop filter selects for

replacement the entry representing the cache line or lines

owned by the fewest nodes. This can be improved by further

locality based algorithm.

3.5x the performance of Cortex-A15 processor.

Frequencies of 2.5 GHz in a 16nm FF+ process and

scalable to higher frequencies.

75% reduction in energy consumption on heavy tasks.

Combining with a Cortex-A53 CPU in big.LITTLE

configurations, saves an additional 40-60% energy.

Smooth performances on multiple light app (e.g.

checking social network, email, news reader…)

Low cost (<250 €)

Notable design

Raw computational power leads to thermal issue. When

not needed must be avoided. If not the measures taken

to react to this issue could be heavy (e.g. thermal

throttling):

Mobile markets are growing and changing year after year,

low-cost is becoming the most important target"

INTEL FAMILY

INTEL ATOM Z3580 [~55$ ]

Asus Zenfone 2 = 350 $

Nokia N1 (tablet) = 250 $

Dell Venue 8 7000 (tablet) = 400 $

BIG.LITTLE FAMILY

SNAPDRAGON 810 [~65$ ]

LG Flex 2 = 700 $

HTC One M9 = 650 $

SAMSUNG EXYNOS 7420 [~30$]

Samsung Galaxy s6 = 750 $

A53 (derived A7) FAMILY

SNAPDRAGON 410 [~30$ ]

Samsung Galaxy A5 = 300 $

HTC desire 620 = 250 $

MEDIATEK MT6735 [~40$ ]

Sony Xperia E4g = 130 $

Lenovo A5000 = 150 $

Some low-cost SoC promise the same (or better

performance) at lower costs: e.g. snapdragon 410 cost

25% more than Mtk comparteur providing 30% less

computational power.

We have seen that different market targets lead to

different meaning of word ENOUGH: enough battery life,

enough performance, enough graphic quality.

To achieve these goals trade-off and different strategies

must be taken into account. Some are better.

http://www.anandtech.com/show/6936/intels-silvermont-architecture-revealed-getting-serious-about-mobile/5

http://www.pcper.com/reviews/Mobile/Dell-Venue-8-7000-Review-Intel-and-Android-Perfected/Battery-Life

http://www.realworldtech.com/silvermont/

http://download.intel.com/newsroom/kits/atom/comms/pdfs/Intel_Atom_Z35XX_FactSheet.pdf

http://www.arm.com/files/pdf/CacheCoherencyWhitepaper_6June2011.pdf

http://www.embedded.com/electronics-news/4419448/Benchmarking-ARM-s-big-little-architecture

http://mobiletoday.it/3227/android/arm-cortex-a72-e-gpu-mali-t-880-tecnologia-per-il-2016.html