SA-1110/Applications Processor Migration

A.2.1 Software Compatibility

Because the PXA250 applications processor uses Intel® XScale™ microarchitecture, the PXA250 applications processor has a different pipeline length relative to the SA-1110. This effects code performance when migrating between the two devices varies because of the number of clock cycles needed for execution. Any application that relies on specific cycle counts, or has specific timing components, will show a difference in performance.

The PXA250 applications processor features: larger caches, Branch target buffering, and faster multiplication, and so many applications run faster than the SA-1110 when running at the same clock frequency.

A.2.2 Address space

The physical address mapping of gross memory regions is not compatible between the PXA250 applications processor and SA-1110. For example, on the PXA250 applications processor, Static chip selects 4 and 5 are lower in memory than PCMCIA, on the SA-1110 they are higher in the memory space.

Changes of this kind could be managed by the Operating System remapping virtual memory pages to new physical addresses. This assumes that the Operating System has basic support for virtual memory, but not if this could be managed by initialization code modifications effecting the same change.

More significantly, memory-mapped registers may have different names, new addresses and different functionality. This impacts all device drivers and register-level firmware, that at a minimum, requires re-mapping register address and changing the default configuration.

A.2.3 Page Table Changes

There are differences in the virtual memory Page Table Descriptors between the SA-1110 and the PXA250 applications processors that impact software execution speed. A new bit has been added to differentiate ARM* compliant operation modes from some features Intel includes such as access to the Mini-Data-Cache.

If any software attempts to explicitly control page table modifications, normally the domain of the Operating System, then that software may need annotation to allow for the extra opportunities the PXA250 applications processor offers.

Any SA-1110 code that explicitly uses the Mini-Data-Cache is executed correctly, but it's ability to utilize a different cache is lost without a page table bit being changed. The impact here is performance not functionality.

A.2.4 Configuration registers

There are numerous device configuration changes in the PXA250 applications processor. You must now select the configuration options for clock speeds such as Turbo Mode. This requirement is not found on the SA-1110.

A-6

PXA250 and PXA210 Applications Processors Design Guide

Page 99 Page 101
Page 100
Image 100
Intel PXA250 and PXA210 manual Software Compatibility, Address space, Table Changes, Configuration registers
Page 99 Page 101

PXA250 and PXA210 specifications

The Intel PXA250 and PXA210 processors, part of the Intel XScale architecture, were introduced in the early 2000s, targeting mobile and embedded applications. They are known for their low power consumption, high performance, and advanced multimedia capabilities, making them suitable for a wide range of devices, including PDAs, smartphones, and other portable computing devices.

The PXA250, which operates at clock speeds ranging from 400 MHz to 624 MHz, features a superscalar architecture that allows it to issue multiple instructions per clock cycle. This enhances the overall performance for demanding applications while maintaining low power usage. It supports a variety of peripheral interfaces, including USB, Ethernet, and various memory types, which contributes to its versatility in different product designs.

One of the key technologies in the PXA250 is the integrated Intel Smart Repeat Technology, which optimizes data processing, thereby reducing the amount of power consumed during operation. This feature is particularly important for battery-powered devices, as it extends the overall battery life, allowing for longer usage times in mobile environments. Additionally, the PXA250 includes a dedicated graphics acceleration unit, which enables enhanced graphics and multimedia performance suited to modern applications at the time.

In contrast, the PXA210 is a more entry-level processor, aimed at cost-sensitive applications. Operating at lower clock speeds, typically around 200 MHz to 400 MHz, it forgoes some of the advanced performance features of the PXA250 while still offering a good balance of performance and power efficiency. The PXA210 is less complex, making it suitable for simpler devices that do not require the extensive capabilities of the PXA250.

Both processors utilize the Intel XScale architecture, which is based on the ARM instruction set. They are built on a 0.13-micron process technology, enabling higher density and lower power consumption compared to their predecessors. With integrated memory controllers and bus interfaces, they facilitate efficient data handling and connectivity options.

In summary, both the Intel PXA250 and PXA210 processors played a crucial role in the evolution of mobile computing by providing powerful processing capabilities with energy efficiency. Their features and technologies enabled device manufacturers to create innovative products that catered to the growing demand for portable devices during that era.
Top Page Image Contents