Making Commodity PCs Fit for Signal Processing

Commodity PCs are on the verge of being capable of performing a variety of signal processing tasks that previously required special purpose hardware. Advances in the speed and width of their processors and internal buses allow these machines to manipulate data at rates that would allow their users to interact with a diverse range of sampled media, such as the raw RF spectrum and ultrasound. However, today's PCs lack an I/O system capable of delivering the appropriate bandwidth to these signal processing applications. These applications demand high continuous throughput I/O that smooths the inter-sample jitter introduced by interrupts, I/O bus latency, scheduling latency, etc. This paper presents a system that provides this functionality. Our system is composed of two tightly integrated parts: a PCI device that provides high raw I/O bus throughput and operating system enhancements to manage the device and provide low overhead transfers across the boundary between kernel and user space. The performance is excellent, providing up to 512 Mbits/sec of continuous throughput for an application. A description of both parts of the system is given, along with performance measurements,and a brief description of an application.