Researchers showed that performing computation directly on storage devices improves system performance in terms of energy consumption and processing time. For example, Riedel et al. [2] proposed an active disk which performs computation using the processor in a hard disk drive (HDD). Their experimental results showed that the active disk-based system had a factor of 2x performance improvement [2]. However, because the performance gap between the HDDs and CPUs becomes larger and larger, the active disk-based improvement is quite limited. As the role of flash memory increases in storage architectures, solid-state drives (SSDs) have gradually displaced the HDDs with higher access performance and lower power consumption. Researchers also proposed an active flash, which performs computation using a controller in the SSD [1]. However, the SSD controller needs to implement a flash translation layer to make the SSD as an emulated HDD for most operating systems. It also needs to communicate with a host interface to transfer required data. The additional computation power can be utilized is quite limited. To maximize the computation power on the SSD, we propose a processor design called storage processing unit (SPU).