Raspberry Pi 1 and 2 compared
A NEON SIMD Extension
The single-instruction multiple data [5] (SIMD) instruction set extension means that the logic in the chip uses one command to processes several pieces of data simultaneously (see the "Extended Instruction Set" box). This technology is especially important for use with multimedia applications responsible for such things as MP3 file decoding, facial recognition in photographs, and greater playback rates for high-definition videos.
The ARM11 of the RPi1 series already had a SIMD extension, but the new Neon instruction set offers significantly more possibilities. The ARM11 operates with 32-bit registers, allowing the simultaneous addition of four 8-bit values.
Neon also introduces 64- and 128-bit registers, paving the way for the addition of up to 16 8-bit values in one computing step. On top of this, the computing unit was given a series of new instructions. Neon handles SIMD instructions with this series depending on application and code quality between 1.5 and 12 times faster than the ARM11 on the RPi1s.
The RPi2B requires an average 3.5 to 4 watts of power. The RPi1B+ was satisfied with 3W. The BCM2835 is still fabricated with 65nm technology, whereas the BCM2836 is manufactured with 28-nm technology. The availability of more transistors allows four modern Cortex-A7 cores instead of only one ARM11 core to be placed on the same area.
Comparing Generations
Comparing the computing power of two processors is not easy, because you must consider the intended purpose, the performance capability of factors such as RAM and cache, and the processor-specific optimizations of the software. The Dhrystone million instructions per second (DMIPS) values determined via the Dhrystone test provide a good approximation [6] when comparing the power of different architectures.
Instead of the 875DMIPS found in the RPi1, the RPi2B has a 6,840DMIPS rating, which indicates a sevenfold increase in computing performance. In practice, the amount of increased performance depends on whether the software allows for parallel processing on the four cores. In many situations, in fact, the performance increase is observed to be even greater, such as when supplementary and faster working RAM accesses the SD card – a slow process – fewer times.
Table 1 provides an overview of the results achieved by the Raspberry Pi compared with results from other currently available single-board computers (SBCs) and a series of computers ranging from those available in earlier days to those found in today's market. The data for devices containing an ARM core are taken from ARM. As a rule, the performance data claimed is usually higher than that observed during actual use. The data of the x86 systems come from real-life measurements, mostly from Sandra Dhrystone [7].
Table 1
Comparisons of Computing Performance
Compared with |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Platform | RAM | Chip | Technology | Architecture | DMIPS/MHz | Cores | MHz | DMIPS | RPi1 | RPi2 |
Raspberry Pi |
||||||||||
Raspberry Pi 1 |
512MB |
Broadcom BCM2835 |
65nm |
ARM1176JZF |
1.25 |
1 |
700 |
875 |
100% |
13% |
Raspberry Pi 2 |
1GB LPDDR2 |
Broadcom BCM2836 |
28nm |
Cortex-A7 |
1.90 |
4 |
900 |
6,840 |
782% |
100% |
Banana Pi |
||||||||||
Banana Pi |
1GB |
Allwinner A20 |
40nm |
Cortex-A7 |
1.90 |
2 |
1,000 |
3,800 |
434% |
56% |
Banana Pi M2 |
1GB |
Allwinner A31S |
40nm |
Cortex-A7 |
1.90 |
4 |
1,000 |
7,600 |
869% |
111% |
Other SBCs |
||||||||||
Beaglebone Black |
512MB |
TI Sitara AM3358/9 |
45nm |
Cortex-A8 |
2.00 |
1 |
1,000 |
2,000 |
229% |
29% |
Hummingboard i2 |
1GB |
Freescale i.MX6 DualLite |
40nm |
Cortex-A9 |
2.50 |
2 |
1,000 |
5,000 |
571% |
73% |
Cubox-i4Pro |
2GB |
Freescale i.MX6 Quad |
40nm |
Cortex-A9 |
2.50 |
4 |
1,000 |
10,000 |
1,143% |
146% |
Odroid C1 |
1GB DDR3 |
Amlogic S805 |
28nm |
Cortex-A5 |
1.57 |
4 |
1,500 |
9,420 |
1,077% |
138% |
Smartphones |
||||||||||
Galaxy S3 Mini (GT-I8190) |
1GB |
ST-Ericsson NovaThor U8500 |
45nm |
Cortex-A9 |
2.50 |
2 |
1,000 |
5,000 |
571% |
73% |
iPhone 5 |
1GB |
Apple A6 |
32nm high-K metal gate |
ARMv7s Swift [Apple] |
3.50 |
2 |
1,300 |
9,100 |
1,040% |
133% |
Game Consoles |
||||||||||
PlayStation 2 |
36MB |
EmotionEngine |
250nm |
RISC, based on MIPS R5900 |
20.34 |
1 |
295 |
6,000 |
686% |
88% |
Apple Computers |
||||||||||
Apple ][e |
64KB |
MOS Technology 6502 |
8,000nm |
MOS Technology |
0.43 |
1 |
1 |
0.43 |
0.05% |
0.01% |
Apple Macintosh 128K |
128KB |
Motorola 68000 |
3,500nm |
CISC |
0.23 |
1 |
6 |
1.4 |
0.16% |
0.02% |
iMac G3 |
32MB |
PowerPC 750 G3 |
260nm |
PowerPC G3 |
2.25 |
1 |
233 |
525 |
60% |
8% |
Intel and AMD PCs |
||||||||||
No Name PC 1 |
64MB |
Pentium II, 300MHz |
350nm |
x86 Intel |
0.91 |
1 |
300 |
273.6 |
31% |
4% |
No Name PC 2 |
384MB |
AMD Duron, 800MHz |
180nm |
AMD Spitfire |
2.81 |
1 |
800 |
2,250 |
257% |
33% |
Dell Inspiron 7520 |
8GB |
Intel Core i7-3632QM |
22nm |
Intel Core i7 |
14.19 |
4 |
2,200 |
99,750 |
11,400% |
1,458% |
Hetzner EQ4 server |
32GB |
Intel Core i7-3770 |
22nm |
Intel Core i7 |
14.19 |
4 |
3,400 |
106,530 |
12,175% |
1,557% |
Upton compares the subjectively observed performance of a RPi2B with that of an AMD Duron CPU running at 800MHz. Equipped with a slim system, a desktop built with this chip would still work quite nicely. Compared with the RPi1 that has something like a Pentium II 300MHz level of performance, this represents significant progress.
The Raspberry Pi Foundation has always mentioned the so-called factor 6, which refers to the speed increase over the old version of the Rasp Pi. This sixfold increase results from the average of several measurements in different areas. For instance SysBench, a multithreaded CPU benchmark, shows that the RPi2B is six times faster. However, the PC may exceed or fall below this rate depending on the application.
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