Memory FAQ for Gaming, Professional Design Software, Operating System

My computer uses PC2700 (DDR333). Can I use PC3200 (DDR400)?

DDR memory was designed to be backward compatible so generally speaking, you can safely add faster memory to your computer. For example, you can install a PC3200 DDR module in a computer that calls for PC2700 DDR. However, keep in mind that faster memory will not necessarily make your system faster. You can't speed up your computer by adding faster memory if other components in your computer (your processor or other memory modules) operate at a slower speed.

Do I have to buy the same size upgrade as the memory module currently installed in my computer or can I mix different sizes?

In newer systems using SDRAM or DDR SDRAM memory, you can use modules of different densities with no problem. For example, if your computer came with a 128MB memory module, you can add a 256MB module for a total of 384MB of RAM. However, if you have a "dual-channel" system and want to take advantage of that technology, you will need to ensure that the modules in each memory slot are the same density.

How can I "max out" the memory on my computer?

Once you have found your computer in the Crucial Memory Advisor™ tool, locate the maximum memory capacity and number of memory slots for your particular computer. Generally speaking, you can determine the largest memory module each slot can take by dividing the maximum capacity by the total number of slots. For example, if your computer has a maximum memory capacity of 2048MB (i.e. 2GB), and has two slots, the largest module you can install in each slot is a 1GB memory module.

However, there are exceptions to this general rule. For example, there are situations where a computer with 4 memory slots and a 2GB maximum memory capacity will accept two 1GB modules. There are also times when a system would only accept a 512MB module at launch, but down the road would take a 1GB module with a BIOS upgrade. This is why it is so important to use the Crucial Memory Advisor™ tool which can alert you to these exceptions.

To completely "max out" the memory on your computer, you may need to actually remove memory modules currently installed and replace them with larger-capacity modules. Using the example above, if your computer has one 512MB module already installed, with one memory slot open, you would need to remove the 512MB and install two 1GB modules to truly "max out" your computer.

The System Scanner results showed my computer's front side bus speed is 200MHz but it's supposed to be 800MHz. What's wrong?

Many newer computers use double data rate or "quad-pumped" front side busses. While the actual front side bus frequency is 200MHz, the enhanced capability of your computer's front side bus allows it to perform like a 400MHz or 800MHz front side bus.

How much memory do you need?

When it comes to adding system memory, the general rule of thumb is the more, the better.

On average, doubling the amount of memory in your system will give you ample "space" to work and make an obvious difference in overall speed, especially with today's memory-hungry applications, such as office programs and graphics-intensive games. You'll be able to run more programs at once, and your system will be less likely to lock up or behave strangely. You'll also find it easier and faster than ever to edit graphics and sound. The bottom line is that adding memory makes your computer more efficient and allows you to do more things at once.

Any time you add RAM, consider this money-saving tip-if the memory upgrade will fill all the slots in your system, get as much memory (megabytes) as you can. This will save you money if you ever want to upgrade down the road. That's because once you fill a system's slots, you have to remove some of the existing memory to make room for new, higher-capacity modules.

How much total memory do you need?

You know that more memory is better, but what's the absolute minimum amount of memory you need? In general, most current operating systems run best with at least 128MB of RAM, and preferably 256MB or more to take advantage of the features the OS has to offer. That's just for the operating system. Then, you need to add more memory for each additional program you plan to run at a given time. To calculate the number, look at the software you're running, and then add the amount of memory required for each application you'll likely run at one time to the amount you need for your operating system. If you're not sure how much memory your software requires, the following charts can help.

What Memory timings, CAS Latency etc?

A. If you look in your BIOS of your PC you will find a range of settings that you can adjust in relation to your memory. These can have a huge effect on not only system stability but also on overall performance. I have read many reviews that don’t take memory timings into account when benchmarking a system. You can make a very quick system very slow if these settings are set up incorrectly. Alternately you can make your system perform a lot better if you learn to tweak these settings. The most common are CAS Latency, RAS to CAS Delay and RAS Precharge. Remember if you set these to aggressively you can make your system unstable.

CAS (Column Address Strobe) Latency - The time from the application of the memory module's CAS address to the appearance of data from the RAM Chips on the module. CAS 2 is therefore faster than CAS 2.5 as it only takes 2 clock cycles in lieu of 2.5.
Active to Read or Write Delay - - The number of clocks between the activation of a particular row address inside the SDRAM's on the module and the issuance of a read or write command to that row.
RAS Precharge - The minimum number of clocks between the completion of one memory access and the beginning of the next. [Bookmark]ECC or (Error Checking and Correction)

What is the difference between ECC and non-ECC (non-parity) memory?

A. If you are unsure of which type you have, just count the number of small black chips on one of your existing memory modules. If the number of chips divides by three evenly, then you need ECC. If the number of chips is does NOT divide evenly by three, you have non-ECC or non-parity memory.
If you plan to use your system as a server or a similar mission critical type machine, you may want to take advantage of ECC. If you plan to use your system for regular home, office, or gaming applications, you are better off with non-ECC. Current technology DRAM is very stable and memory errors are rare, so unless you have a need for ECC, you are better served with un-buffered DDR SDRAM.

What is meant by Registered memory?

A. "Registered" is a means of "Buffering" the memory in SDRAM. This means that the clock signal is boosted across the entire array of memory chips so that the computer sees a clean sharp clock signal instead of a weakening clock signal as it progresses along the length of the memory path. Registered memory must be supported by the system board and cannot be mixed with "Un-buffered" modules. You must have only registered memory to use registered memory. This is a further means of eliminating the possibility of errors when reading the data in memory and is used when the data returned from memory is extremely critical, such as in scientific or financial calculations where the integrity of the data is CRITICAL. It also allows a module to be built using more chips, allowing for larger capacity modules to be made.

What types of DDR memory are available?

A. There are currently three types of DDR memory available.
1. PC1600 DDR provides a 1.6GB/second throughput of data.
2. PC2100 DDR, provides a 2.1GB/second throughput of data.
3. PC2700 DDR, provides a 2.7GB/second throughput of data
4 PC3200 DDR , provides a 3.2GB/second throughput of data

How Much Memory Is Enough?

A. People will tell you that you can never have enough memory, but that's not necessarily always true. Some operating systems have issues with large amounts of RAM and your applications may not ever use it if you have excessive amounts. Most motherboards have limits on the amount of memory that your system can have or that the board can handle. If you're building a new PC, be sure to check this out with the manufacturer before purchasing a motherboard.

What is Virtual Memory ?

A. Virtual memory is simply your hard drive trying to act like a RAM chip. Your operating system creates a temporary storage area on your Hard drive and uses it to store some of the information it is using at a given point in time. Since the hard drive is so much slower than real memory, programs stutter and sometimes crash when the hard drive has to do a job it was never designed for. If you have enough physical memory your virtual memory is rarely needed. There are only two solutions to this problem: close some programs until virtual memory is no longer needed, or add more physical memory. With current memory prices are so low and affordable it, the latter solution is always preferable.