| What does it do?
RAM provides the Mac’s processor with short-term storage with high access speeds. The Mac’s processor can’t directly access information on hard disks, CDs, and so on, so data are fetched from these into RAM, where the processor can edit words, pictures, play music, and so on. The data that you’ve altered can then be saved out to disk when you want. How does it work?
Your computer’s RAM is controlled by the processor itself, and is tightly coupled to it, through the fastest cache memory. The core of the Mac OS is loaded into RAM during startup, and additional modules (such as QuickTime components) are loaded when needed. RAM contains both program code (the instructions to the processor as to what to do), and data (the letters, pixels and other raw materials on which software operates). Your Mac keeps a careful map of where each is in memory, and each program is allocated an area of memory reserved for its own use. That allocated memory is freed up again when you quit the application. What can go wrong with it?
Provided you have the right type of memory modules for your computer, it’s generally very reliable as long-lasting as the processor itself. Sometimes the modules aren’t properly seated in their connectors when installed, which can produce intermittent problems. Specifying the right type of memory is complex, and is a task best carried out by a dealer, so all you should provide is the Mac model details. Apple System Profiler, TechTool Pro and other utilities can check out your RAM. How can I upgrade it?
There are two shortcuts to save having to buy more real memory: turning on virtual memory allows your Mac to pretend that it has more memory, by using hard disk space as a supplement. Connectix offers RAM Doubler, which works similarly, for many older versions of the Mac OS. Otherwise, you’ll need to increase the amount of memory actually installed, by having more modules plugged into their special slots on the motherboard. Further info
Most good books about computers explain RAM, and some detail the differences between RAM modules. Web sites include the home of the Guide to RAM Upgrades (GURU) at www.newerram.com; and Apple’s memory guide, in Acrobat (PDF) format, at asu.info.apple.com/swupdates.nsf/artnum/n10084 | |
