Ricerc@Sapienza

In this paper, an emulation environment for approximate memory architectures is presented. In the context of error tolerant applications, in which energy is saved at the expense of the occurrence of errors in data processing, approximate memories play a relevant part. Approximate memories are memories where read/write errors are allowed with controlled probability. In general these errors are the result of circuital or architectural techniques (i.e. voltage scaling, refresh rate reduction) introduced to save energy.

In this work we present AppropinQuo, a flexible and configurable emulator for embedded platforms with approximate memory. The emulator includes models of the effects of approximate memory circuits and architectures, that depend on the internal structure and organization of the cells. The ability to emulate a complete platform, including CPU, peripherals and hardware-software interactions, is particularly important since it allows to execute the application as on the real board, reproducing the effects of errors on output.

This paper describes the analysis, in terms of tolerance to errors on data, of a H.264 software video encoder; proposes a strategy to select data structures for approximate memory allocation and reports the impact on output video quality. Applications that tolerate errors on their data structures are known as ETA (Error Tolerant Applications) and have an important part in pushing interest on approximate computing research.

In this work we present an emulation framework for hardware platforms provided with approximate memory units, called AppropinQuo. The specific characteristic of AppropinQuo is to reveal the effects, on the hardware platform and on software, of errors introduced by approximate memory circuits and architectures. The emulator allows to execute software code without any modification with respect to the target physical board, since it includes the CPU, the memory hierarchy and the peripherals, capturing as well software-hardware interactions and faults due to approximate memory units.