Research and Critically Review three General-Purpose Embedded Processors - Essay Example

Running head: RESEARCH AND CRITICALLY REVIEW THREE GENERAL-PURPOSE EMBEDDED PROCESSORS Research and Critically Review three General-Purpose EmbeddedProcessors ------------------------------------- Abstract Wireless technology advancement had been initiated with the improvement in the microprocessor designs to accommodate a host of features and applications, like, web browsing, 3-D gaming, camera, video etc. The basic architectural designs that have been improvised are RISC and CISC processors. The technological development has seen wide usage and application of fixed length instructions of a RISC processor, being fast and simple, in conjunction with DSP based microcontrollers and media accelerators to fulfill the demands of today’s mobile customers. The leading companies like, Intel, Motorola and Texas Instruments etc, have contributed significantly towards the growth of mobile processors. The paper compares and critically examines three different products (embedded microprocessors) on the basis of five comparison criteria; power consumption, code density, peripheral integration and chipsets, multimedia accelerators and performance. Research and Critically Review three General-Purpose Embedded Processors Introduction Microprocessors came into existence with the advent of computer technology. Since then, there has been a steep increase in the technological advancement with each new technology replacing the old counterpart in a matter of a year or two. Power consumption and dissipation, among these processors, was not a cause of concern as the issue could be easily addressed by use of fans with processors to keep them cool apart from providing an air conditioned environment. This arrangement sounds good for desktop applications only, while mobile applications warrants good performance in open environment with stored power sources (batteries) and no cooling mechanism (Schlett, Manfred., 1998). With the wireless technology boom and rising demands of services on mobile platforms like, PDAs, cellular and smartphones, the embedded processors faced a number of challenges, of which power management (for longer battery life), processing speed (for better access to services) and memory management became far to important (Conte, Thomas M., 1997). In the subsequent paragraphs, the paper would discuss the basic criteria for judging the overall performance of mobile embedded processors. Further, the paper would critically examine three brands of embedded processors from different companies and compare them. Criteria for Comparing Microprocessors Embedded microprocessors have a number of associated properties and features of which the following five offer best criteria for differentiating and estimating the performance:- Power consumption of an embedded processor, used for mobile applications, is generally done with an established benchmark for comparison – MIPS/watt (Schlett, Manfred., 1998). The power consumption is noted for three different modes of operation; active (when the clock signal traverses to every part of the processor), Standby (when only a few instructions are processed , memory refreshing is affected and goes to active mode on receiving an external interrupt) and power off (the clock is switched off). Code density refers to the complexity and density owing to code length (Schlett, Manfred., 1998). CISC processors exhibit better code density than RISC processors due to complex instruction set in CISC, while RISC utilizes a fixed length instruction code. However the RISC architecture offers simple and fast instruction decoding. It is not always advisable to integrate a large number of peripherals and chipsets with the processor. This would increase complexity and may not lead to desired results. It may further, create power consumption problems. A possible way out could be a separate chipset for applications. Multimedia accelerators refer to the application software that are an important need of the day with demands of mobile net access, video, camera, gaming and other applications (Schlett, Manfred., 1998). These can be implemented by use of a separate microcontroller and enhanced instruction set functionality. Price performance ratio, measured as MIPS/unit currency is the last criteria on which the processors can be compared. SH Processors SH is an application processor for mobile communication developed by Renesas Technology Corp. based on RISC processor. It can support large range of multimedia functions like camera, video, music, Java gaming, etc. The processor achieves very low power consumption, owing to arrest of leakage current, in both active and standby modes. The basic processor architecture includes a dual processor (SHx) core and IPs for processing multimedia functions. The processor core consists of following subparts (Kamae, S., Irita, T., Tsukimori, A., Tamaki, S., Hattori, T. and Yoshioka S., 2005):- A central processor unit along with a DSP microcontroller. A data cache (32 KB, 4-way set associative instructions ). TLB (4 entry instruction and 64 entry unified). XYRAM and URAM (16 KB and 256 KB respectively). IPs like MPEG-4 accelerator, video processing, LCD control, camera interface, and 3-D graphics accelerator. The processor utilizes techniques like hierarchical clock trees and pointer based pipelines to achieve power saving and enhancing battery life in active mode and standby mode respectively. The processor also features two modes of standby – ‘ultra’ and ‘resume’. The performance further enhanced by the dual nature of the processor where the processor load is shared. The performance power efficiency achieved by above feature is about 4500 MIPS per watt (Kamae, S., Irita, T., Tsukimori, A., Tamaki, S., Hattori, T. and Yoshioka S., 2005). The low power consumption is achieved by bringing the leakage currents down to as low as 86 microamperes and 12 microamperes in ‘resume’ and ‘ultra’ standby mode respectively (Kamae, S., Irita, T., Tsukimori, A., Tamaki, S., Hattori, T. and Yoshioka S., 2005). The various media accelerators used enhance performance in processing. StrongARM and XScale These processors are products of Intel, one of the leaders in processor technology. StrongARM and XScale are based on ARMvx instruction set with XScale being the new version of the company. XScale exhibits better signal processing performance and supports almost all multimedia applications, like, camera, 3-D graphics, video, 3-D Java gaming. It also houses a microcontroller (DSP) for running the application and thus is faster than StrongARM. In addition a wireless router has also been incorporated in the design. The processor is being used in high end PDAs and cellular phones (Clarke, D., 2002). Salient characteristics of ARMv6 are given as under:- It is a 32-bit RISC processor, 64 data buses between processor unit, instruction and data caches. It supports media processing with power controller leading to very low power consumption. Power consumption levels are about 0.5 Watt for 200 MHz processing speed. The technology is capable of achieving a performance of 750 MIPS for a power consumption of 40 to 450 mW (Clarke, D., 2002). It consists of an 8-stage scalar pipeline, issuing one instruction at a time. The parallel pipeline concept is utilized and ALU, multiply-accumulate and load-store instructions are executed simultaneously. Out of order execution of instructions is also implemented unless; the execution does not depend on prior execution of certain instruction (Georgescu, Mihai D., 2003). 64 entry, 4-state branch target access cache enables it to save five clock cycles per correct prediction that is done based on past outcomes (Georgescu, Mihai D., 2003). It follows a non-blocking memory operation (Georgescu, Mihai D., 2003). DragonBall MX DragonBall MX is a processor designed by Motorola. The processor is based on ARM9 microprocessor and operates at speeds upto 200 MHz. The various constituent modules and peripherals of the processor are LCD controller, static RAM, USB support, A/D converter, MP3 and MPEG-4 controller and Bluetooth technology enabled application processor (Georgescu, Mihai D., 2003). The processor has applications in PDAs, cellular mobiles and smartphones. The architecture of ARM9 is similar to the ARMv6, with absence of a number of facilities, being an older instruction set of ARM series. Critical Analysis Having seen the three embedded processors, the question arises as to which one is best suited for mobile application. Here, as is evident, from the features, XScale takes a lead over others in the amount of peripheral integration. DragonBall MX uses an inferior technology as compared to XScale, which is based on the ne4w ARM series instruction set and is far faster in processing of signal as well as application. However SH has a unique advantage of power saving and dual processing. All the processors utilize RISC architecture as a base and hence, the code densities in all the cases are more or less similar. XScale’s high speed processing along with high performance to power ratio makes it the clear leader. Conclusion Embedded microprocessor technology has been evolving since early 1980s with the development of wireless technologies. The ever increasing demand of facilities has challenged the bandwidth and power constraints of mobile communication platforms. Research in the field of processors have yielded techniques like dual processing, parallel processing, hierarchical clock tree, etc to considerably bring down the power consumption and enhanced processing speed of embedded processors. XScale based of ARMv6 is one of the leading processor developed by Intel in the embedded processor field. References Kamae, S., Irita, T., Tsukimori, A., Tamaki, S., Hattori, T. and Yoshioka S. (2005). SH-Mobile - Low Power Application Processor for Cellular. IEEE Journal. 5349-5352. Schlett, Manfred. (1998). Trends in Embedded Microprocessor Design. Computer (IEEE). 44-49. Georgescu, Mihai D. (2003). Evolution of Mobile Processors. IEEE Journal. 638-641. Clarke, D. (2002). Mobile Processors Begin to Grow up. Computer (IEEE). 22-25. Conte, Thomas M. (1997). Challenges to Combining General Purpose and Multimedia Processors. Computer (IEEE). 33-37. Read More