There are such things as cheap , ninety day , or generic RAM, which is actually sold, and doesn't meet the minimum standards of the JEDEC
(Joint Electron Device Engineering Council), for use in computers. But it is still sold, and un-informed people, still buy it.
RAM can generally be divided into a few classes:
(Excepting Performance or Overclockers RAM, which is made to the highest tolerances)Premium or Lifetime Warranty
: This RAM is made from Identical chips, all tested and meeting the assemblers standards, all from the same chip manufacturer and lot.
The capacitors and resistors are of the highest standard, and exceed the JEDEC standard, and all are installed on a circuit board which is thicker than required .
The final product is tested to confirm that it is stable at the rated speed.One Year Warranty
: Very close, but may include memory chips from different batches, although still the same manufacturer.
The circuit board tends to be at least one ply thinner, and the resistors and capacitors may have more variance.
These still meet the JEDEC standards, and are tested to make sure they are stable at the specified speed.OEM
: These are intended for sale to a manufacturer, not for resale, although they are often sold retail.
Often if you buy two sticks, you will find that they have memory chips from different manufacturers.
They still meet standards (the chips are certified to meet the manufacturers specifications), but are often yet another ply thinner, and once again, may have more variance in the tolerance of resistors and capacitors, and may use fewer, than on higher quality RAM.Generic or 90 Day RAM
: This is the lowest quality you will generally encounter.
Often these are made of leftover chips; ones salvaged from returned and failed RAM,
RAM designed to run at a higher speed which failed and became unstable.
They're put on really thin boards, which do not meet the JEDEC standard.
They rarely have even the minimum number, and quality of resistors and capacitors, recomended by the JEDEC .
Also, if you touch the RAM anywhere except the edges, you should know that the oils and salts in your skin are corrosive, and will eventually damage the ram.
And if you touch it without observing anti-static precautions, you can cause damage, which may show up immediately, or somewhere down the line.
This is why I always recommend that you spend the extra money to buy Quality Name Brand RAM
with a lifetime warranty.
I also prefer to buy all RAM at one time when possible, and at a minimum, make sure it has identical specifications (easiest method, make sure it is same manufacturer and model).
These companys manufacture quality RAM:CrucialKingstonCorsair
Also, check out the information on their sites.
There's a lot of good information about RAM, definitely worth the read.
Here's an article you might want to check out:Understanding, Identifying and Upgrading the RAM in your PC
Whatever you do, don't buy "cheap" RAM.
This is one area where it's definitely, "You get, what you pay for".