Raspberry Pi 1 and 2 compared

Other Models

On the basis of strong demand for the RPi2B, all of the BCM2836 SoCs available to the Foundation are used for the current model. The Compute Module 2, which needs a carrier board to convert its I/O to "normal" plugs, will probably be available at the end of this year at the earliest.

A trimmed down Model A version of the RPi2 with at least 512MB of working memory cannot currently be produced for the envisioned sales price of $25. Less RAM would reduce the price; however, Upton considers 512MB mandatory for a four-core system.

The Raspberry Pi Display [15] for the display serial interface (DSI) should be available for purchase this year. Currently, it is still undergoing tests for its electromagnetic compatibility.

Conclusions

The RPi2B is well suited as a versatile desktop system for less demanding users who want to accomplish some text processing alongside surfing the Internet and viewing online streams on YouTube. It is a quiet, compact, economical, and energy-saving computer that outstrips classic, low-end desktop systems.

Performance on the desktop represents a quantum leap over the performance of the first generation. Still, there is room for improvement in some areas. The Foundation recently invested quite a bit in web browser performance. As a result, the work implementing the Wayland protocol came to a standstill. It is not yet clear whether the performance for Wayland will get help in the future. However, the Foundation clearly is working on hardware-accelerated graphics performance.

So, what is in the works for the future? The revolution started with the RPi2B could tackle the market for mobile devices and other areas of application. Many potential uses would open up and resonate with the community with the appearance of an open hardware platform with increased performance, an integrated display, and a battery.

The possibilities for the BCM2836 have in any event come to the end of the road. At the least, a third generation Rasp Pi ought to be equipped with Gigabit Ethernet and a number of USB ports directly on the SoC. All of the bottlenecks would then have been resolved if there were also an upgrade of the working memory to 2 or 4GB.

The Pi's ARMv7 architecture

ARMv7 processors are understandably compatible with the instruction set of the ARMv6 predecessor, making it possible to continue using software like Raspbian that was developed for the first generation Raspberry Pis on the RPi2B. The OS kernel and some routines adapted in assembly language that developers wrote specifically for the RPi1 do not carry over to the RPi2B.

However, the software will need to be compiled specifically for the ARMv7 to realize the full potential of the new processor. The Raspberry Pi Foundation is currently working on plans that describe the best way to do this. It may suffice merely to offer some of the libraries for Raspbian compiled independently for both ARM architectures (ARMv6 and ARMv7).

The Cortex-A7 theoretically can support up to 1TB of working memory, thanks to its 40-bit memory mapping unit (MMU). However, the actual architecture of the BCM2836 with its 1GB of RAM reaches its maximum because 2 bits of the 32-bit storage address are used for cache.

A maximum of 1GB can be addressed with 30 bits. A hypothetical Model 2 B+ based on the same BCM2836 SoC would not permit further memory upgrades. The memory bus now runs with 450MHz in contrast to the RPi1, which has a standard speed of 400MHz for its memory bus.

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