rgc@wam.umd.edu (Ross Garrett Cutler) (06/15/91)
Hello, I'm finally ready to buy some RAM, but I've heard that parity RAM on the NeXT induces an extra wait state. Does anyone know *how* much this will slow down my NeXT (compared to non-parity RAM). (I'm looking for a numerical answer, not "a lot" or "not much"). Maybe someone who has parity RAM could run a simple bench mark, then turn off the parity, and run it again. Thanks very much! Ross. -- Please email -- I'll summarize. Ross Cutler University of Maryland, College Park Internet: rgc@wam.umd.edu
John_Graves@next.com (John Graves) (06/20/91)
For NeXTcubes and NeXTstations, enabling parity memory will add one clock cycle to the access time to each 32 bit word for both reads and writes initiated by either the processor or the DMA. For NeXTstation Color, enabling parity memory will add one clock cycle to the access time to each 32 bit word for reads initiated by the processor. Parity memory does not effect the performance of processor writes or DMA operations. Parity applies only to DRAM (main memory), not to VRAM (video memory). Parity does not effect anything which fits in the processor's cache (like small benchmarks). Parity can only be used if all banks of DRAM contain parity SIMMs and parity is enabled in the bootROM (v63 or later). What does this jargon mean? You'll feel some performance degradation when using parity memory on NeXTcubes and monochrome NeXTstations, with a less noticeable effect on NeXTstation Color machines. - John Graves NeXT Computer, Inc. Hardware Engineer 900 Chesapeake Drive John_Graves@next.com Redwood City, CA 94063