Nonvolatile memory, such as resistive RAM (ReRAM), is compatible with standard CMOS logic processes, allowing a sizable main memory system to be integrated into a CPU's die. ReRAM bitcells are fabricated within crosspoint subarrays that leave the bulk of transistors underneath the subarrays vacant. This permits placing the memory system over the CPU, improving area, parallelism, and power. Our work quantifies the impact of integrating ReRAM into a CPU's die. When integrating ReRAM over CPU logic, the best area efficiency occurs when 48% of the die is covered with ReRAM. The CPU's area increases by 18.8%, but we can recoup 35.5% of the die area by utilizing the free transistors underneath the crosspoint subarrays. When integrating ReRAM over CPU cache, up to 85.3% of the cache can be covered with ReRAM. Our work also shows that on-die ReRAM can support very high bandwidth through massively parallel memory access. At 28 nm, 4–16k independent ReRAM banks could be integrated onto the CPU die, providing 512–1024–GB/s peak bandwidth. At more advanced technology nodes, 5–10 TB/s may be possible.

中文翻译：

---

分析基于 ReRAM 的主存储器与 CPU 芯片的单片集成

非易失性存储器，例如电阻式 RAM (ReRAM)，与标准 CMOS 逻辑工艺兼容，允许将相当大的主存储器系统集成到 CPU 的芯片中。ReRAM 位单元是在交叉点子阵列内制造的，这使得子阵列下方的大量晶体管空置。这允许将存储器系统置于 CPU 之上，从而提高面积、并行度和功耗。我们的工作量化了将 ReRAM 集成到 CPU 芯片中的影响。在 CPU 逻辑上集成 ReRAM 时，当 48% 的裸片被 ReRAM 覆盖时，面积效率最佳。CPU 的面积增加了 18.8%，但我们可以通过利用交叉点子阵列下方的空闲晶体管来收回 35.5% 的芯片面积。在 CPU 缓存上集成 ReRAM 时，ReRAM 可以覆盖高达 85.3% 的缓存。我们的工作还表明，片上 ReRAM 可以通过大规模并行内存访问来支持非常高的带宽。在 28 nm 处，4-16k 独立 ReRAM 组可以集成到 CPU 芯片上，提供 512-1024-GB/s 的峰值带宽。在更先进的技术节点上，5-10 TB/s 可能是可能的。