The layman’s guide to computer memory.

Posted: February 13, 2012 by ryanlecocq in Off-topic, Technology

RAM, Solid State, Flash.  You most likely use devices with these words on them every day.  An understanding of the design and operation of the device isn’t required to use it, but a lot of things will click into place if you have one.  I truly believe that understanding anything from automechanics to computers is a series of big puzzle pieces that fall into place and make sense of a bunch of facts you already knew.  When you understand exactly what a vehicle transmission does, all of the parts on it have obvious purposes.  Computers are no different and once you understand the basic purpose and function of the components, other things will become clear.

The first invention that paved the way for all of these technologies is the memory wafer.  The idea is to make a material that contains different molecules that will react differently (and predictably) when an electric current is put through them.  The basic technologies birthed from this concept (RAM, LCD screens) do not hold the pattern when the current in removed.  So just as your LCD tv doesn’t hold the last picture displayed when you turn it off, computer RAM dumps the data it’s holding on shutdown and starts fresh every boot.  Creating a material like this that was stable and not volatile, took 20 years of further research.

Flash and Solid State are truly a leap of chemistry and metallurgy.  The above technologies are just volatile substances that can be made to act predictably with a series of exact currents.  Creating a material in which the charges would naturally oppose each other in the exact pattern desired is a modern marvel that will definitely be one of the keys to a Star Trek future.  It doesn’t require a constant charge to hold it’s memory, it just stays exactly how it’s arranged.  While a Hard Disc Drive has to spin and charge each sector one at a time, the SSD just needs to be zapped from one end like an LCD screen or RAM.  As a result it’s silent and suffers no mechanical wear.

You may have gathered from all that the extreme complexity of the manufacturing process.  This actually explains both the failure rate and the different speeds of these technologies.  For example on RAM, if you’ve ever tested a bad stick you know that one bad sector means the whole thing is trash.  So every single tiny sector has to take charge exactly as expected or the whole thing is useless.  Beyond this we get into tolerances.  The reason one RAM stick is rated at 1333MHz and another at 1866MHz is not because they were necessarily manufactured to be different.  Somehow one just came off the assembly line more perfect than the other and as a result it can perform it’s function at a higher rate of current without error.

This can apply to RAM and even Flash drives, but SSDs are a different story.  A Solid State Drive is such a high-end device that each one has to be perfect or it gets thrown out.  It can’t operate in a wide variety of settings and is generally designed to be as close to the maximum speed of it’s interface as possible (SATA2/3 etc).  While some SSDs are faster than others, it usually has to do with the controller chip associated with it, not the manufacture quality.

That’s just the basics, but hopefully a few things will make sense to you now that were Greek before (unless you’re Greek in which case things that were American before).

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