Adding RAM to Your Computer: How Much Can You Add?

Next to upgrading the processor or CPU, adding RAM or memory has the largest effect in speeding up a computer. Adding RAM to a computer gives the operating system more room to hold volatile memory resulting in fewer reads from the hard drive and a place to hold information a program may need now and in the near future.

Before heading out to your local store or surfing to an online computer hardware dealer, you need to understand the three limitations to adding more memory to your computer. These three limitations dictate the total amount of memory your computer can handle. Each limitation can be classified as a physical, component, or operating system restriction.

Adding memory to a computer is a matter of buying the correct type of RAM for your computer and physically installing it onto the mainboard (or motherboard) of your computer. The mainboard is a complicated circuit board to which everything in the computer connects. Hard drives, DVD burners, the CPU, video cards, and RAM all connect to the mainboard. RAM is simply inserted into the memory slots located on the mainboard. However, as with all electrical appliances, sticking your hands into a computer can be dangerous even if the computer’s power plug is disconnected. Your computer’s power supply includes powerful capacitors that hold a charge even when the computer is unplugged. Coupled with the ability to damage internal components from static electricity, it is better to leave the addition of computer memory to a qualified technician.

Regardless of the theoretical memory limitations set forth by an operating system or component, some mainboards simply do not have enough slots available for additional RAM. Each mainboard has anywhere from one to eight (sometimes more) but typically four memory slots where memory can be inserted. Without at least one free slot, there is no place to add RAM. In this case, there are two possibilities. First, the existing RAM can be completely replaced with new, larger memory modules (sometimes called “sticks” of RAM). Larger means that the individual memory modules have larger capacities (two gigabytes versus one gigabyte) not that they are physically larger. Second, the mainboard can be replaced with one that has more memory slots. This solution is far more complicated and requires an analysis of what technologies your computer has and what mainboard is compatible with these technologies. Unless you have money to burn and expert knowledge of swapping out a mainboard, the first solution is far more desirable.

As discussed above, some mainboards have only a few memory slots making it necessary to discard the memory currently in a machine for new, larger memory modules. However, sometimes the mainboard itself is the limiting factor in adding RAM to a computer. Some mainboards are only capable of addressing (recognizing) a certain memory ceiling making it redundant to add more memory above this ceiling. Just because a mainboard has open memory slots does not guarantee that it will be able to recognize and use all memory inserted into the slots. The best way to learn how much memory the mainboard is capable of addressing is to consult the mainboard’s manual or visit the manufacturer’s website for this information. If you insert memory in mainboard and it is not showing up in the operating system, it may be a limitation of the mainboard.

Most home computer users are unaware of that operating systems come in various “flavors” which dictates the maximum amount of memory that can be recognized. Microsoft Windows 95, 98, ME, 2000, and XP are/were 32-bit operating systems meaning that they could address a maximum of 4 gigabytes of memory at one time. This number is calculated as 2 to the 32nd power or 4,294,967,296 bytes of total memory. 32-bit operating can address memory up to this maximum giving 32-bit operating systems a 4-gigabyte memory limitation. Any memory above this limit is unaddressed (ignored). After the release of Windows XP, a 64-bit version of the operating system was released removing this limitation. In addition, Windows Vista and Windows 7 come in both 32-bit and 64-bit versions allowing purchasers to decide which operating is better for them. Using the same logic above, 64-bit operating systems have a theoretical limit of about 18,446,744,073,709,551,616 bytes (2 raised to the 64th power) or 16 exabytes of memory. However, due to other hardware and practical limitations it is unlikely that 64-bit operating could ever address this amount of memory given contemporary hardware design.

Since the majority of people use 32-bit operating systems, it is worth discussing the 4-gigabyte memory limitation in detail. It turns out that computers running 32-bit operating systems and with 4-gigabytes of memory installed are not able to address the entire amount of RAM. This is because the 32-bit memory limitation includes a limitation on all cached memory in the system including video card memory, memory cached by the CPU, and various other types of memory in a computer. These computers typically can address only about 2.5 to 3.2 gigabytes of RAM leaving the remaining RAM unused.

There are several significant limitations to adding memory to a computer. It is not simply a matter of having free memory slots; in fact, even with no memory slots free it is possible to simply remove the current memory and add new memory to increase the amount of RAM in a computer. Often, computer manufacturers will put in low memory modules (usually 1 gigabyte) into each memory slot because they are cheaper. Memory modules containing 2 gigabytes are more expensive but do allow you to add more total memory. In addition, paying attention to the operating system may tell you whether adding RAM will be useful. Increasing the memory of a 32-bit computer from 3 gigabytes to 4 gigabytes will most likely be a waste of money since the operating system will not be able to address but about 2.5 to 3.2 gigabytes of the memory.