CompuServe Messages

Ron, Disk caches don't run programs from within the cache…but rather they simply buffer the most recently read/written sectors from the disk in RAM. Thus, depending on the size of the cache…to load a program you end up with 2 copies in RAM, the running program, and the cache'ed program read from disk. Cache programs show their greatest useability during things like text editing, database operations or any other operation that is constantly reading and/or writting data. As an example, suppose a text editor reads in 100 sectors (and thus those 100 sectors are also in the cache…presuming it's large enough). You edit the file, but only change data in one small area. On writing the file out, the cache only writes out that one small area…possibly only 1 sector. Thus avoiding writting out the 99 unchanged sectors and thus speeding up things greatly. Now if you suddenly decide to re-edit that file, it's already in the cache…thus takes essentially 0 time to read in. The same idea applies to database access and so forth. CPU caches operate the same way…except with program instructions and data thus speed up execution. But neither of them gives you 1x size of the program only in RAM, they end up with the loaded program, plus some amount in the cache thus you end up with somewhere between 100% and 200% of the program in some form of RAM. Don