RAM needs

RAM stands for Random Access Memory.  The RAM in your computer is where everything happens.  Programs reside on disk but, in the computer architecture proposed by John von Neumann and universally used in computers since, programs must be read into memory and can only be executed there.  The data also resides in RAM memory.  There is another type of memory, ROM or Read Only Memory, which is used for invariant programs and starting or default data.

RAM is cheap.

It is important to have enough RAM to do what you need to get done.  We are talking here about things that are loaded into memory, programs like your web browser, your email program, WORD or some such, etc.  The data they need like the current web page, images, the document you are working on, an email message, etc. are also needed in memory.  If you scrimp on RAM and have too many programs in your start-up, you can run out.  In this case the operating system, OS, lets you pretend you have enough RAM by using virtual memory.  This is like the FED letting the government think it has enough money by printing virtual money.  The OS implements virtual memory by writing the excess to a file on your disk drive called the paging file.  RAM works in small multiples of nano-seconds or billionths of a second or 10-9 seconds.  The disk drive on the other hand works in small multiples of milliseconds or thousandths of a second or 10-3 seconds.  Dividing these two gives a speed ratio of one million to one.  In other RAM operates 1,000,000 times faster that a disk.  That’s a real performance cliff you fall off.  Symptoms of a dearth of RAM include the screen not popping from one image to another when you bring something to the foreground.  Instead it slowly paints its way down the screen.  Another symptom is the gray not-responding boxes you get upon system shutdown.  These programs got shuffled off to the disk and didn’t get read back in in time to respond to the shutdown signal from the operating system.

Extreme cases can lead to a condition we call thrashing.  In this instance the actual useful work done for you goes down.  Here’s a scenario.  You click on a WORD document to edit it.  WORD is read into memory, opens the file and asks for the first block of data.  At this point your anti-virus program which is on disk has to be read in to memory to scan the file.  Memory is full.  We have to bump out something.  We bump out WORD, read in the anti-virus, scan the file, and the anti-virus relinquishes control back to the OS which bumps it out onto the disk and reads in WORD again.  This can be painful.

OK.  Enough of this.  How much do you need?  Well that depends on what kind of operating system you use and what you are doing with it.  There’s an old saw about a woman not being able to be too rich or too thin.  Not having enough RAM is disastrous, but after you have enough architecture limits and diminishing returns enter the scene.  Here are some variations.

  • Windows XP 32-bit needs nowadays 1 gigabyte or more.  Light users can get away with 768 megabytes.
  • Any 32-bit version of Windows can utilize only a little over 3 gigabytes because the architecture can’t address more than four gigabytes or 232 and some of the address space is reserved for I/O, input/output devices.  Probably your most cost effective buy for Vista and Windows 7 32-bit systems is two DIMMS/SODIMMS of the proper type and speed of two gigabytes each.
  • Windows 7 64-bit and Vista 64-bit can utilize an entire 4 gigabytes of RAM.  In fact its what I have on my own homebrew computer, and right now I’m using 56%.
  • One would need eight gigabytes if one were a heavy Photoshop user.
  • Most fancy motherboards in the hobbyist realm top out at sixteen gigabytes, so that is a practical limit.

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