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Fumio ARAKAWA Tomoichi HAYASHI Masakazu NISHIBORI
Parallel execution of the carry propagate adder (CPA) and leading non-zero (LNZ) detector that processes the CPA result is a common way to reduce the latencies of floating-point instructions. However, the conventional methods usually cause one-bit errors. We developed an exact LNZ detection circuit operating in parallel with the CPA. The circuit is implemented in the floating-point unit of our newly developed embedded processor core. Circuit simulation results show that the LNZ circuit has a similar speed to the CPA, and it contributes to make a small low-power FPU for an embedded processor core.
Fumio ARAKAWA Motokazu OZAWA Osamu NISHII Toshihiro HATTORI Takeshi YOSHINAGA Tomoichi HAYASHI Yoshikazu KIYOSHIGE Takashi OKADA Masakazu NISHIBORI Tomoyuki KODAMA Tatsuya KAMEI Makoto ISHIKAWA
A SuperHTM embedded processor core implemented in a 130-nm CMOS process running at 400 MHz achieved 720 MIPS and 2.8 GFLOPS at a power of 250 mW in worst-case conditions. It has a dual-issue seven-stage pipeline architecture but maintains the 1.8 MIPS/MHz of the previous five-stage processor. The processor meets the requirements of a wide range of applications, and is suitable for digital appliances aimed at the consumer market, such as cellular phones, digital still/video cameras, and car navigation systems.