CompuServe Messages

Not true. There is nothing that is inherently incompatible between virtual memory and multimedia. A full-blown VM system should let you specify what pages are not eligible for swapping. This can be used to keep realtime performance realtime. When you anayze realtime programs, most of the code (and, usually, most of the data) does not need to be realtime. There are usually only a few parts that absolutely need to be kept in memory at all times. The other parts can be brought in as needed. I write realtime software for VAXen running VMS (an extremely virtual memory oriented OS). Doing an analysis on a VAX 11/750 (a machine that is slower than a 68020), we found that a page fault from disk took 50-70 milliseconds. This is fast enough for most human oriented interaction. Things that needed faster response time are locked into memory. BTW – As far as multitasking is concerned, this system was also running things like networking software, FORTRAN compiles, editing files, etc., while running the realtime code. Chris