RAM : Computer Hardware Buyers’ Glossary

Most memory sold now-a-days does not have even error detection logic, much less error correction ( ECC (Error Correcting Code)). When you get an error, the program continues, but with wrong information. This may not be all that important if you are just playing a game, but it could be crucial if you are doing an income tax return. Parity memory is a very simple form of error detection without correction. Because of alpha particle emissions, memory can be expected to make errors every so often, even when it is functioning perfectly.

To upgrade RAM, you must check the motherboard manual too see what kinds and combinations of memory it can take. If you have no manual, try the website of the motherboard or computer manufacturer. You could even ask the vendor who sold you the computer, but that information is usually not trustworthy. You can also try the Kingston memory configurator. The catch is it only list RAM for which Kingston makes a replacement part. Before you shop you need to know if the memory is:

• 72-pin SIMM (Single Inline Memory Module), or 144-pin SODIMM or 168/pin or 184-pin, 224-pin DIMM (Dual In-line Memory Module). The more pins the more the chip can address and the more data it can transfer at once.
• Capacity per module: 64 MB, 128 MB, 256 MB, 512 MB, 1024 MB/1 gig, 4 gig, 8 gig.
• speed: PC-66, PC-100, PC-133, PC-800, PC-1600/DDR200, PC-2100/DDR266, PC-2700/DDR333, PC-3200/DDR400, DDR2-667 MHz, DDR3 1333 MHz, DDR3 1600 Mhz, DDR3 1866 MHz, DDR3 2000 MHz, DDR3 2133 MHz, DDR3 2400 MHz
• type: fast page mode, EDO (Extended Data Out), SDRAM (Synchronous Dynamic RAM), ESDRAM (Extended Synchronous Dynamic Random Access Memory), SLDRAM (Synchronous Link Dynamic RAM), DDR (Double Data Rate), RAMBUS/RDRAM, DDR2, hypertransport, DDR3.
• voltage: 5 volts, 3 volts, 1.5-1.7 volts.
• buffered or unbuffered.
• plain or ECC (error correcting).
• Single or dual ported/channel
• Memory timing e.g. 9-9-9-24. The smaller the numbers the better.
• Other modifiers such as Cl2, Cl3 and registered.

The easiest way to handle this is to buy the RAM and motherboard from the same source and leave it up to them to ensure they match, or look in the motherboard specs for the list of vendors of compatible vendors and models of RAM and CPU (Central Processing Unit) combinations.

Most new machines use DDR RAM, value machines SDRAM and premium machines RDRAM (Rambus Dynamic Random Access Memory).

New machines tend to come configured with too little RAM for that class of machine in order to shave the advertised price. Nearly always you should buy the offered RAM upgrade to double the available RAM. You should be thinking of 4-16 Gig to start. The other advantage of buying up front in the RAM type may not always be easily available.