A bstract-In this paper, potential performance improvements of the memory hierarchy of RISC-systems for implementations employing 3-D-technology are investigated. Relating to RISC-systems, 3-D ICs will offer the opportunity for integrating much more memory on-chip (i. e. on one IC or 3-D IC with the processor). As a result, the second-level cache may be moved on-chip. The available on-chip cache may alternatively be organized in three levels. Investigations were also performed for the case of the main memory being integrated on-chip. Current restrictions of conventional RISC-system implementations, such as limited available transistor count for on-chip caching, confined data bus width between processor-chip and the off-chip second-level cache, long access times of the second-level cache, strongly limit the achievable performance of the memory hierarchy and may be either removed or at least substantially reduced by the use of 3-D ICs. To evaluate the performance improvements of implementations employing 3-D ICs, a model based on measured miss rates and on an analytical access time model is used. The average time per instruction is employed as the performance measure. Results of extensive case studies indicate, that substantial performance improvements depending on implementation, cache sizes, cache organization, and miss rates are achievable using 3-D ICs. A comparison of four optimized implementations all with a total cache size of approximately 1 MB yielded performance improvements in the range of 23 YO to 31 % for the implementations employing 3-D-technology over the conventionally implemented system. It is concluded, that 3-D-technology will be very attractive for future high performance RISC-systems, since the system performance depends vitally on the performance of the memory hierarchy.