Why Does More Memory Make My Computer Run Faster?
Why does more memory make my computer run faster? It Doesn’t!
OK – Then why are you always advised to get more memory for your computer?
First – you need to understand what determines the speed of your computer – then you can understand why more memory is needed.
The most important factor in the computer's speed is the system clock speed of CPU – the processor. Basically, the faster the CPU (of the same type), the faster the computer runs. The CPU speed is measured in GigaHertz (GHz) – you’ll see numbers like 2.8GHz, 3.0GHz, etc. (Mobile Processors, such as those used in Intel Centrino laptops, will be in the range of 1.5GHz, 1.7GHz, etc.)
There are different types of processors – including the newer Hyper-Threading and Dual-Core CPUs. Hyper-Treading CPUs act like there are 2 processors in the computer. Dual-Core CPUs actually have 2 CPUs one the one chip. Each of these processors has speed advantages over the traditional CPU running at the same speed
Related to the CPU speed and affecting the computer's speed is the Front Side Bus (FSB) speed. This is how fast the processor talks to other parts of the computer, including the memory. The FSB speed is measured in Megahertz (MHz) – and you’ll see numbers like 533MHz, 800MHz and 1066MHz. Again, faster is better. Memory also comes in different speeds to match the FSB speeds. Using memory slower then the FSB speed slightly reduces the overall speed of the computer. Using memory faster then the FSB speed doesn’t speed up the computer past the rated FSB speed. It is best to match the memory speed to the CPU’s FSB speed.
Another CPU feature that affects the computer speed in CACHE. CACHE is memory on the CPU that stores program instructions in memory on the chip. This CACHE memory is accessed and used much faster then the computer's memory. Since program instructions are often used over and over - the computer runs faster when the instructions are in the CACHE since it doesn't have to retrieve these instruction from memory. Simply, the more CACHE on the CPU, the faster the computer. CACHE is measured in MB - and CPUs usually have 512MB, 1024MB (1GB) or 2048MB (2GB).
The final item in the speed equation is the hard disk. Factors that determine the speed of the hard disk, or the transfer rate, are the rotational speed, the interface type, and the on-board cache.
The faster the hard drive spins – the quicker in can access and transfer the data on the drive. Common rotational speeds are 5400RPM, 7200RPM and 10000RPM. Almost all hard drives in PCs are 7200RPM.
Interface types include SCSI (Small Computer System Interface), IDE (Integrated Drive Electronics) and SATA (Serial Advanced Technology Attachment). SCSI drives are usually found in higher end equipment, like servers. IDE drives – the most common interface – can have data transfer rates up to 100MB/s (MegaBits/Second). The new SATA drives have transfer rates of 150MB/s for SATA and 300MB/s for SATA-2. Here – faster is better. Most manufacturers are switching to SATA drives. If your computer has a SATA-2 interface, using SATA-2 drives is best.
The final hard drive factor is CACHE. CACHE is memory on the hard drive that holds the latest information written to or read from the drive. Memory reading and writing is much faster than hard disk reading and writing. Computers often use the same hard drive data over and over – so if it is available in the hard drive cache, the CPU can get to it much faster. Most hard disks have 8MB cache, with some of the new SATA-2 drive having 16MB cache.
Here is a list of the factors affecting computer speed:
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CPU Speed
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Front Side Bus Speed
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Memory Speed
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Hard Disk Speed
How does this all factor in to the speed of the computer?
Look at the following diagram:
This is a representation of your CPU, Memory and Hard Disk.
All programs, including Windows, Internet Explorer, Office, AOL, Email, games and any other program your run is ‘processed’ in the CPU. The instructions for the program and all the data the programs need are kept in memory. (The hard disk – often referred to as memory is actually storage. The CPU cannot make direct use of what is stored on the hard disk directly – it has to be transferred to memory.)
When you start a new program, the instructions that make the program work are transferred from the hard disk into memory. The CPU then uses the instructions in memory while running the program. All programs also use additional memory while running. For example, when you run Word, the document you are editing is kept in memory. When you finish editing an 'save' the document, it is written to the hard disk.
As was mentioned earlier, reads and writes to the memory are much faster then reads and writes to the hard drive. Lets look at what happens when we edit a Word document:
When you launch Word, there is a delay while the Word program is transferred from the hard disk to memory. (Microsoft keeps you occupied by showing it's "splash screen" as Word loads.) Next you open the document – and it is also transferred from the hard disk to memory. Now you can use the program and edit the document, and for the most part – the hard disk is never used until you save the document. Now, the document that is in memory is written to the hard disk and cleared from memory. When you exit Word, the program is also cleared from memory.
That’s the process – but why does more memory help?
Everything that is running needs to be in memory. This includes Windows, your anti-virus program, Internet Explorer and all those little programs that put the little icons in your system tray. And all of these programs are in memory at the same time.
The amount of actual memory, the RAM, is
finite. As you open more and more programs the amount of free memory
decreases. At some point, the program you open and their data will need
more memory then is free. Windows – being a nice obedient operating system
will still open the program - even though there isn't enough free memory. To do this, it has to free up some memory.
It does this by moving the information that is in part of the memory to a
portion of the hard disk. This portion is called ‘virtual memory’ and is
set aside automatically by Windows on your hard disk.
In the example in the diagram - Quicken is loading, but there isn't enough free memory.
Windows determines that the program idle the longest (in this example) is Excel.
So, Excel, and all it's data is copied to the hard disk in the area set aside
for Virtual Memory. Then Windows frees up the memory Excel was using and Quicken
now has enough space to load.
When you want go back to Excel (which is now in Virtual Memory), Windows will gladly move it back into memory, but it will send another program, the one that has now been idle longest, to the virtual memory. This is called swapping.
If you have very little memory – let’s say 256MB – then you could run out of free memory after 1 or 2 programs are loaded, and there will be lots of disk swapping. Again, the computer has to go through the slow process of swapping and your computer seems to ‘hang up’ while these programs are being swapped. Have you ever had a Word document open at the same time you are browsing the Internet and you have your Quicken open? You go to type in word, and nothing shows up on the screen. Then, all of a sudden everything catches up. This was most likely caused by disk swapping.
If you increase the computer memory to 512MB, 1GB or more, your computer can have many more programs open at the same time without the need to ‘swap’ them to virtual memory. Having more memory greatly reduces the number of disk swaps, eliminating the delays while programs and data are written to the slower hard disk.
So, even though your computer is not ‘running’ faster, it appears to run faster simply because there is much less of the slower disk-swapping. You don’t have to wait for the computer to catch up.