Seagate Cheetah Family of Disk Drives

Seagate Technology, the world’s leading provider of data storage products for Internet, business and consumer applications, has leveraged the ARM® processor architecture, tools and software to introduce new products into the Cheetah family of enterprise-class disk drives. Announced in May 2002, Seagate’s Cheetah products lower the total cost of ownership (TCO) for IT managers through high reliability and increased capacity and performance. The data storage and access metrics for these devices are impressive:

• Capacity of 18 to 146 gigabytes
• Spindle speeds of 10,000 and 15,000 RPM
• I/O at 2 gigabytes/second
• Seek time of 3.9 milliseconds

The ARM architecture is well regarded among embedded processor designers for its high-performance, low-power consumption characteristics. These attributes have been critical to the success of the ARM architecture in the wireless handset and PDA markets. Beyond these portable, batterypowered applications, however, ARM is achieving traction in important, fast-growing markets such as automotive control systems, home networking and storage devices. While the advantages of low power coupled with high performance are an important element of any IC design, ARM has increased the value of its processor architecture by offering a suite of RealView™ development tools and apabilities that streamline the product development cycle and provide Partners with a complete and reliable embedded processor solution.

Inside the Controller
At the heart of every Hard Disk Drive (HDD) is a controller device, which is responsible for managing all aspects of drive operation. These next-generation disk drives from Seagate use a ARM966E-S™ core-based hard disk drive (HDD) controller from ARM semiconductor Partner, LSI Logic Corporation. The tasks performed by the HDD  controller are complex and varied, and require advanced processing capabilities, making the ARM architecture an ideal fit for high-performance HDD controller designs.

The ARM Advantage: Partnership
But implementation of the ARM966E-S cores by LSI Logic is only one element of ARM’s overall contribution to HDD control solutions. Seagate’s development and introduction of the Cheetah product line highlights the advantages of ARM Partnership through every phase of the design process. ARM’s investment with multiple Partners worldwide allows disk drive OEMs like Seagate to benefit from the industry’s premier highperformance, DSP-enhanced, debug-friendly real-time control solution. The result for OEMs is a less expensive development cycle that delivers competitive products to market faster. These are the same challenges facing all product designers, but are especially important to those in markets with shrinking ASPs, as is the case with storage devices. Once the ARM architecture has been selected for implementation, OEMs can tap into an extensive network of ARM Partners to supply ARM core-based and ARM corecompliant HDD controllers.

Development Support
Superior performance is crucial in any data storage application, but so is the ability to debug the processor, ensuring the embedded system – and, subsequently, the whole evice – operates as intended. ARM offers a suite of RealView development software and powerful, real-time debug tools that can be used to expedite disk drive design and verification by allowing OEMs to debug their silicon, exercising program control and observing ample data to track elusive bugs, even at high clock rates. Design problems within a disk drive must be identified in as “real-world” a scenario as possible, preventing costly delays that may occur later in the development cycle, or even once units are deployed in the field. For ARM Partners, real-time debug makes use of on-chip In-Circuit Emulator (ICE) logic called EmbeddedICE-RT™ (‘RT’ for real time), which is already an integral part of the ARM core. The Multi-ICE® interface unit provides debugging of multiple embedded processors through a JTAG port, whilst still allowing critical events, such as interrupts, to proceed as normal. The RealMonitor™ debugging software, is a real-time extension to the ARM Developer Suite™.

RealMonitor provides excellent debug visibility into the embedded systems, but like any ICE-based debug method, it only gives the designer system information at a single point in time. ARM has taken debug solutions one step further and introduced real-time trace debugging – the objective being to view the exact flow of events that occurred in the CPU core, in real time. Here, an Embedded Trace Macrocell (ETM) is placed on chip. The ETM performs two key tasks: it provides triggerfiltering functions (similar to those found in a logic analyzer) and compresses information, intelligently selecting the minimum details needed – usually branch and conditional outcomes – to reconstruct the program flow off chip. The signals carrying this information run through a short ribbon cable to a trace point analyzer (TPA), such as the ARM MultiTrace™ unit. The TPA, in turn, connects to a host PC through a high-speed Ethernet connection.

Running on a PC is a suite of Trace Debug Tools (TDT) that, like the ARM RealMonitor software, are an extension of the ARM Developer Suite software. This ARM technology enables HDD controller software to be exercised and observed with critical routines running at full speed. The ability to fully reconstruct program flow and relate that back to the original source code means the designer can locate hard-to-find bugs when every part of the disk drive system is operating and interacting in a way that no simulation could ever recreate.

Summary
Seagate has incorporated all elements of ARM design methodology to deliver the Cheetah family of products. ARM, for its part, is able to provide the industry’s leading suite of embedded processor technologies through collaboration with the ARM Partnership. As high-performance data storage products like Cheetah disk drives from Seagate become more prevalent, the ARM architecture and development systems will play an increasingly valuable role in providing a start-to-finish embedded processor solution.

Evolution of the ARM Solution 
ARM’s industry leading Real-Time Control and Debug solutions are themselves examples of the power of partnership. Many companies have contributed to the systems described here, each an expert in their fields. Cirrus Logic and Agere (Lucent) were instrumental in helping to define the “E” extensions to the ARM instruction set that added valuable DSP capabilities to a number of ARM cores and optimized the ARM966E-S core for embedded hard real-time applications like HDD control and, more specifically, the processing of servo algorithms. The enhanced DSP capability of the ARM966E-S core is one example of ARM’s work with Partner companies to develop a complete embedded processor solution that meets the cost and performance requirements of OEMs like Seagate. 

These debug tools were developed by ARM in conjunction with Agilent, Tektronics and Noral, combining the expertise of multiple companies to deliver a robust development and debug solution to OEMs. Furthermore, ARM worked with Palmchip to create the ARM Embedded Trace Macrocell (ETM), which allows trace of an HDD controller during real-time operation. The Partnership surrounding ARM’s design solutions continues to grow, adding broad industry support and giving the user a wider choice of tools solutions to build their ARM Powered® devices.

ARM, ARM Powered, AMBA and MultiICE are registered trademarksof ARM Limited. ARM966E-S, EmbeddedICE-RT, RealMonitor, RealView, ARM Developer Suite and MultiTrace are trademarks of ARM Limited. All other brands or product names are the property of their respective holders. “ARM” is used to represent ARM Holdings plc (LSE: ARM and Nasdaq: ARMHY); its operating company ARM Limited; and the regional subsidiaries ARM INC.; ARM KK; ARM Korea Ltd.; ARM Taiwan; an ARM France SAS; and ARM China.

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