Abstract. This paper discusses the hardware foundations of the cryptosystem employed by the Xbox TM video game console from Microsoft. A secret boot block overlay is buried within a system ASIC. This secret boot block decrypts and verifies portions of an external FLASH-type ROM. The presence of the secret boot block is camouflaged by a decoy boot block in the external ROM. The code contained within the secret boot block is transferred to the CPU in the clear over a set of high-speed busses where it can be extracted using simple custom hardware. The paper concludes with recommendations for improving the Xbox security system. One lesson of this study is that the use of a high-performance bus alone is not a sufficient security measure, given the advent of inexpensive rapid prototyping services and affordable high-performance FPGAs.
PowerPC 620 microprocessor: A high performance superscalar RISC processor. COMPCON 95, 1995.
While there has been an abundance of recent papers on hardware and software approaches to improving the performance of memory accesses, few papers have addressed the problem from the program's point of view. There is a general notion that certain programs have larger working sets than others. However, there is no quantitative method for evaluating and comparing the memory requirements of programs. This paper introduces the bandwidth spectrum for characterizing the memory requirements of a program's instruction and data stream. The bandwidth spectrum measures the average bandwidth requirement of a program as a function of available local memory. These measurements are performed under the most Idealized conditions of perfect knowledge and perfect memory management. As such, they represent the lower bounds on the memory requirements of programs. We present the bandwidth spectrums for a set of 22 benchmarks and show how they can be used in the comparison of memory requirements and I/O requirement. The bandwidth spectrums also offer a convenient method to weigh the trade-off amongst instruction issue rate, local memory capacity and bandwidth into local memory.Using the bandwidth spectrum, we show that at issue rates of four or less, bandwidth usually scales linearly with the issue rate. At higher issue rates, bandwidth can often scale superlinearly with respect to issue rate. Finally, we also investigate the effects of varying the input sets on the bandwidth spectrums.
While there has been an abundance of recent papers on hardware and software approaches to improving the performance of memory accesses, few papers have addressed the problem from the program's point of view. There is a general notion that certain programs have larger working sets than others. However, there is no quantitative method for evaluating and comparing the memory requirements of programs. This paper introduces the bandwidth spectrum for characterizing the memory requirements of a program's instruction and data stream. The bandwidth spectrum measures the average bandwidth requirement of a program as a function of available local memory. These measurements are performed under the most Idealized conditions of perfect knowledge and perfect memory management. As such, they represent the lower bounds on the memory requirements of programs. We present the bandwidth spectrums for a set of 22 benchmarks and show how they can be used in the comparison of memory requirements and I/O requirement. The bandwidth spectrums also offer a convenient method to weigh the trade-off amongst instruction issue rate, local memory capacity and bandwidth into local memory.Using the bandwidth spectrum, we show that at issue rates of four or less, bandwidth usually scales linearly with the issue rate. At higher issue rates, bandwidth can often scale superlinearly with respect to issue rate. Finally, we also investigate the effects of varying the input sets on the bandwidth spectrums.
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