On Tuesday, November 12, 2002, at 12:30 PM, Eugene Lee wrote: > On Tue, Nov 12, 2002 at 11:10:53AM -0600, Jeremy Derr wrote: > : > : All Unixes have Virtual Memory (although, not the same kind of VM > : that's in OS 9). The VM in OS X serves to provide the Protected > Memory > : that makes OS X more stable than OS 9. OS X, like all Unix OS's, does > : not function without this (or at least, does not function well). > > Actually, VM does not provide any sort of protected memory. Protected > memory is often implemented directly by the OS (and with some help of > the local CPU). Virtual Memory is just a form a secondary storage for > pieces of primary memory to get stored to.
let me rephrase my statement, then. in most UNIX OS's, protected memory does not function without some sort of VM. in UNIX, it's actually called 'swap', and while providing what looks like VM on the surface, is almost entirely different. It's mechanism is just like VM, but it serves a completely different purpose -- in OS 9 and Windows, VM works to make your computer behave as if it has more memory than it really does.... that is, 512MB RAM + 513MB VM = 513MB available memory. In a UNIX, you usually have exactly as much Swap as Physical. It doesn't function to expand the amount of available memory to the system, it functions to keep an accurate map of what apps are using what sectors of memory, swap inactive RAM to disk so that active apps can use that sector, and a few other minor things. It's the 'mapping' function of swap space that allows UNIX's to have Protected Memory. -- G-Books is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Check our web site for refurbished PowerBooks | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> G-Books list info: <http://lowendmac.com/lists/g-books.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:G-Books@;mail.maclaunch.com> To unsubscribe, email: <mailto:G-Books-off@;mail.maclaunch.com> For digest mode, email: <mailto:G-Books-digest@;mail.maclaunch.com> Subscription questions: <mailto:listmom@;lemlists.com> Archive: <http://www.mail-archive.com/g-books%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
