Computational RAM

Computational RAM or C-RAM is random-access memory with processing elements integrated on the same chip. This enables C-RAM to be used as a SIMD computer. It also can be used to more efficiently use memory bandwidth within a memory chip. Computational RAM or C-RAM is random-access memory with processing elements integrated on the same chip. This enables C-RAM to be used as a SIMD computer. It also can be used to more efficiently use memory bandwidth within a memory chip. The most influential implementations of computational RAM came from The Berkeley IRAM Project. Vector IRAM (V-IRAM) combines DRAM with a vector processor integrated on the same chip. Reconfigurable Architecture DRAM (RADram) is DRAM with reconfigurable computing FPGA logic elements integrated on the same chip.SimpleScalar simulations show that RADram (in a system with a conventional processor) can give orders of magnitude better performance on some problems than traditional DRAM (in a system with the same processor). Some embarrassingly parallel computational problems are already limited by the von Neumann bottleneck between the CPU and the DRAM.Some researchers expect that, for the same total cost, a machine built from computational RAM will run orders of magnitude faster than a traditional general-purpose computer on these kinds of problems. As of 2011, the 'DRAM process' (few layers; optimized for high capacitance) and the 'CPU process' (optimized for high frequency; typically twice as many BEOL layers as DRAM; since each additional layer reduces yield and increases manufacturing cost, such chips are relatively expensive per square millimeter compared to DRAM) is distinct enough that there are three approaches to computational RAM: Some CPUs designed to be built on a DRAM process technology (rather than a 'CPU' or 'logic' process technology specifically optimized for CPUs) includeThe Berkeley IRAM Project, TOMI Technologyand the AT&T DSP1. Because a memory bus to off-chip memory has many times the capacitance of an on-chip memory bus, a system with separate DRAM and CPU chips can have several times the energy consumption of an IRAM system with the same computer performance. Because computational DRAM is expected to run hotter than traditional DRAM,and increased chip temperatures result in faster charge leakage from the DRAM storage cells,computational DRAM is expected to require more frequent DRAM refresh. A processor-in-/near-memory (PINM) refers to a computer processor (CPU) tightly coupled to memory, generally on the same silicon chip.