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Aucbvax.5597 fa.unix-wizards utzoo!decvax!ucbvax!unix-wizards Sun Dec 27 08:59:20 1981 Foreign Memory Problems >From CSVAX.pag@Berkeley Sun Dec 27 08:45:04 1981 (This was sent once before, but without success I believe; so here we go again). After lengthy performance analysis of our 11/70 UNIX, we determined that the biggest bottleneck was swapping (avg 5-10 swaps/sec, as much as 25 swaps/sec during heavy use). We had 512KB of core memory, and decided to double it with an additional 512KB. Due to cost considerations we purchased a Plessy PM-SJ11 MOS memory system (which connects to existing DEC MJ11 core memory). So now our response is really great, right? WRONG! There has been a noticeable slowdown in overall response time. In fact, it is even slower in single user mode! (The file system checks take longer). Performance analysis indicates that the only real difference is that swapping has decreased to near nil, other factors (context switches, system calls, buffer hits, char and block i/o, interrupts) remain the same. In fact, the system is equally slow even if the new memory is not being used. So it has been bothering me to come up with an explanation for this strange behavior. Can anyone think of an explanation (hardware, hopefully)? More details of complete memory system: addr. range hardware ----------- -------- 000-128Kb 128KB DEC MJ11B core in one chassis 256-512Kb 256KB Trendata/Standard Memories core (separate chassis) 128-256Kb 128KB DEC MJ11B core in 2nd chassis 512-1024Kb 512KB Plessy PM-SJ11 MOS & terminators

The order of the list is also the cabling order (ie, Trendata memory lies between two DEC boxes, and memory is terminated in Plessy box). Soon we will scope the system for memory cycle time, but haven't done that yet. We are also writing a memory timing test. Any insight into this problem will be greatly appreciated. Thanks, peter gross CSVAX.pag@BERKELEY

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