COVID-19: We have spent the last several days and weeks learning about the coronavirus (COVID-19) and how it is impacting all of us. As of right now DMS (Data Memory Systems) is still open and shipping packages but there will be delays. Inventory changes daily and it can be hard to get new stock with certain businesses being forced to close due to the pandemic. As things change we will update the site. Please be safe and smart.

• WHAT IS RAM MEMORY?
• WHY DOES MY PC NOT RECOGNIZE THE ENTIRE 4GB OF MEMORY I INSTALLED?
• HOW CAN I DETERMINE WHETHER I AM RUNNING A 32-BIT OR A 64-BIT VERSION OF THE WINDOWS OPERATING SYSTEM?
• WHY DO I NEED MORE MEMORY?
• HOW MUCH MEMORY DO I NEED?
• WILL MORE MEMORY SPEED UP MY INTERNET BROWSER?
• HOW DO I KNOW ITS TIME FOR MORE MEMORY?
• WHAT IS SDRAM? (OBSOLETE - SEE DDR INFO)
• WHAT DOES PC66, PC100 AND PC133 SDRAM MEAN? (OBSOLETE - SEE DDR INFO)
• CAN I USE PC133 OR PC100 SDRAM IN MY 66MHz PC? (OBSOLETE - SEE DDR INFO)
• SHOULD I BUY PC100 OR PC133? (OBSOLETE - SEE DDR INFO)
• WHY WON'T MY MOTHERBOARD ACCEPT A PC133 AT 133MHz BUS SPEED? (OBSOLETE - SEE DDR INFO)
• WHAT IS DDR? (UPDATED FOR DDR3, DDR4, DDR5)
• WHAT TYPES OF DDR ARE AVAILABLE? (UPDATED FOR DDR3, DDR4, DDR5)
• WILL MY MACHINE RUN FASTER WITH HIGHER SPEED DDR? (UPDATED FOR DDR3, DDR4, DDR5)
• WHAT IS DIRECT RAMBUS? (OBSOLETE - SEE DDR INFO)
• HOW DO I KNOW IF I NEED PARITY, NON-PARITY, OR ECC, NON-ECC MEMORY?
• HOW TO TELL ECC, PARITY MEMORY FROM NON-ECC, NON- PARITY MEMORY?
• WHAT IS THE PERFORMANCE DIFFERENCE BETWEEN ECC, PARITY AND NON-ECC, NON-PARITY?
• CAN I MIX AND MATCH ECC, PARITY AND NON-ECC, NON-PARITY?
• WHAT DOES REGISTERED SDRAM MEAN? (UPDATED FOR DDR)
• CAN I MIX REGISTERED AND UNREGISTERED MEMORY?
• WHAT DOES BUFFERED MEMORY MEAN?
• CAN I MIX BUFFERED AND UNBUFFERED MEMORY?
• WHAT ARE BUFFERED EDO AND FPM DIMMS? (OBSOLETE - SEE DDR INFO)
• WHAT IS CAS LATENCY?
• PERFORMANCE DIFFERENCES BETWEEN DIFFERENT CAS LATENCIES
• CAN DIFFERENT LATENCY PARTS BE MIXED?
• HOW DIFFICULT IS IT TO INSTALL ADDITIONAL MEMORY?
• THE DIMM SLOT RETAINING CLIPS WILL NOT LOCK
• CAN YOU MIX AND MATCH MODULES OF DIFFERENT SIZES?
• DOES IT MATTER WHICH SLOTS THE MEMORY IS INSTALLED IN?
• IF YOU GET AN ERROR MESSAGE "INVALID SYSTEM DISK"
• YOU HAVE 512MB INSTALLED AND WINDOWS SAYS OUT OF MEMORY (UPDATED FOR MODERN SYSTEMS)

WHAT IS RAM MEMORY?

If you haven't worked with computer hardware before, it can be easy to confuse your hard drive with RAM memory. However, your hard drive is not the same thing as RAM memory (Random Access Memory). You can think of your hard drive as being like a file cabinet. It's a good place to store a lot of information for a long time. Your RAM memory is like the top of your desk. This is where your system stores the information you're currently working on. RAM is about 100 times faster than your hard drive (depending on the type). However, your hard drive can store information after the power is turned off, while RAM cannot. Your system needs both memory and a hard drive (or SSD) to operate properly.

WHY DOES MY PC NOT RECOGNIZE THE ENTIRE 4GB OF MEMORY I INSTALLED?

The maximum amount of memory can be limited not only by the motherboard but also the operating system.
A 32-bit Windows system will only see 3GB or 3.5GB. A 32-bit system is the most commonly used, though most modern PCs run on 64-bit architecture. A 64-bit system will see and use significantly more memory (well beyond 4GB).

HOW CAN I DETERMINE WHETHER I AM RUNNING A 32-BIT OR A 64-BIT VERSION OF THE WINDOWS OPERATING SYSTEM?

Generally, a computer's bit count indicates how much data it can process, the speed with which it can process the data, and also the memory capacity. The bit count of the operating system installed on the computer should match the bit count of the computer in order to optimize the computer's performance. Use your system information or control panel settings to determine which version you are running. (Note: Microsoft's support links change frequently, search 'How to check if PC is 32-bit or 64-bit' for the latest guide).

WHY DO I NEED MORE MEMORY?

Upgrading your memory is one of the easiest and most cost-effective ways to upgrade your computer, for a significant boost in performance. A memory upgrade is useful for users who work with large files, have many applications or browser tabs open simultaneously, or use memory intensive applications such as games, CAD, or graphics and video editing software.

HOW MUCH MEMORY DO I NEED?

The type of software applications you are using and the number of programs you open at a time have a direct correlation to how much you need on your system. Today's recommended minimum for a Windows/macOS PC is typically **8GB**. For comfortable multitasking and most modern gaming, **16GB** is recommended. If you are a professional content creator, a gamer who streams, or a power user running virtual machines, **32GB or more** will provide the best performance.

WILL MORE MEMORY SPEED UP MY INTERNET BROWSER?

Internet browsing speed depends on a huge number of factors, including your connection speed, server load on the site you're visiting, and the other components in your system. You will probably notice the biggest improvement from additional RAM if you have many browser tabs open (which consume a lot of memory) or if you switch between your browser and other memory-intensive applications often.

HOW DO I KNOW ITS TIME FOR MORE MEMORY?

There are several signs indicating it may be time to upgrade your memory. If you see your mouse pointer turn into a loading icon for significant periods of time, if you hear your hard drive *excessively* working (if you have an older HDD) or if your computer seems to work much more slowly than you expect, the reason is probably insufficient memory. When the memory is full, your system transfers data to the hard drive (or SSD). This is called 'paging' or 'swapping'. Since the hard drive is considerably slower than DRAM, your system seems slower altogether.

WHAT IS SDRAM? (OBSOLETE - SEE DDR INFO)

SDRAM (Synchronous Dynamic Random Access Memory) is the foundational technology for modern memory, but this specific term usually refers to the older Single Data Rate (SDR) generation. Modern systems use **DDR (Double Data Rate)** technology (DDR3, DDR4, DDR5), which significantly improves speed and efficiency. DMS (Data Memory Systems) specializes in the latest DDR generations.

WHAT DOES PC66, PC100 AND PC133 SDRAM MEAN? (OBSOLETE - SEE DDR INFO)

These names refer to older Synchronous DRAM (SDRAM) standards based on the Front Side Bus (FSB) speed (66MHz, 100MHz, 133MHz). Modern DDR standards are named differently, often reflecting the overall data transfer rate. See the updated DDR section below for modern speed ratings (e.g., DDR4-3200 or PC4-25600).

CAN I USE PC133 OR PC100 SDRAM IN MY 66MHz PC? (OBSOLETE - SEE DDR INFO)

Older SDRAM modules were generally backward compatible (running at the slowest supported speed). However, modern DDR generations (DDR3, DDR4, DDR5) are **NOT backward compatible**. They have different physical notches and voltages, meaning a DDR4 module will not physically fit or function in a motherboard designed for DDR3 or DDR5, and vice versa. Always check your system's specifications before purchasing memory from DMS (Data Memory Systems).

SHOULD I BUY PC100 OR PC133? (OBSOLETE - SEE DDR INFO)

For modern systems, you should purchase the memory generation (DDR3, DDR4, or DDR5) and speed that is officially supported by your CPU and motherboard. Generally, you should buy the fastest speed your system supports, as memory will run at the speed of the slowest component (either the RAM itself, the CPU's memory controller, or the motherboard's maximum supported speed).

WHY WON'T MY MOTHERBOARD ACCEPT A PC133 AT 133MHz BUS SPEED? (OBSOLETE - SEE DDR INFO)

Modern memory speed issues are typically resolved in the motherboard's **BIOS/UEFI** settings, often by enabling an "XMP" (Extreme Memory Profile) or "DOCP" profile. This allows the system to recognize the memory's advertised speed. Always ensure your motherboard has the latest BIOS revision, which can improve compatibility and speed stability for DDR3, DDR4, and DDR5 modules.

WHAT IS DDR? (UPDATED FOR DDR3, DDR4, DDR5)

DDR (Double Data Rate) is the current standard for system memory, significantly faster and more power-efficient than older SDRAM. Each generation offers improvements:

• **DDR3:** Older standard (pre-~2014) with speeds up to 2133 MT/s. Operates at 1.5V or 1.35V (Low Voltage).
• **DDR4:** Mainstream standard (post-~2014) with speeds up to 3200 MT/s and higher. Operates at 1.2V.
• **DDR5:** Newest standard (post-~2020) offering significant performance gains and higher density. Operates at 1.1V.

These generations are **NOT compatible** with each other due to physical notch differences and required voltages. They will only work in motherboards specifically designed to use that generation.

WHAT TYPES OF DDR ARE AVAILABLE? (UPDATED FOR DDR3, DDR4, DDR5)

Modern DDR memory is typically listed by its generation, effective clock speed (MHz/MTs), and throughput (PC-naming). Examples of common speeds offered by DMS (Data Memory Systems) include:

• **DDR3:** PC3-10600 (1333MHz), PC3-12800 (1600MHz)
• **DDR4:** PC4-21300 (2666MHz), PC4-25600 (3200MHz)
• **DDR5:** PC5-38400 (4800MHz), PC5-41600 (5200MHz), and higher

**Note:** The PC-naming convention (e.g., PC4-25600) reflects the theoretical maximum bandwidth in MB/s.

WILL MY MACHINE RUN FASTER WITH HIGHER SPEED DDR? (UPDATED FOR DDR3, DDR4, DDR5)

Generally, all DDR is backward compatible in speed (meaning a faster module will run at a slower system speed), but **NOT backward compatible in generation** (DDR4 cannot run on a DDR3 board).
If your PC has a maximum supported speed of, say, DDR4-2666, and you install a DDR4-3200 module, the memory will only operate at 2666MHz unless overclocking profiles (like XMP) are enabled and supported by the system. However, buying a faster module (like DDR4-3200) can sometimes offer tighter timings (latency) or prepare you for a future motherboard upgrade. Your memory will only run as fast as the slowest link in your system (the memory module, the motherboard, or the CPU's memory controller).

WHAT IS DIRECT RAMBUS? (OBSOLETE - SEE DDR INFO)

RAMBUS (RIMM™) was an older, proprietary memory architecture that is now obsolete and has been superseded by the widespread adoption of DDR technology (DDR3, DDR4, DDR5).

HOW DO I KNOW IF I NEED PARITY, NON-PARITY, OR ECC, NON-ECC MEMORY?

The general rule of thumb in deciding what type of memory you need is to look at what's already installed in your system or what your motherboard/server manual requires. To find out if you have ECC (Error-Correcting Code) or non-ECC memory, count the number of chips on the module.
For traditional memory modules (DIMMs): If the total number of chips is evenly divisible by three (e.g., 9 or 18 chips), the module is typically ECC or parity. If not (e.g., 8 or 16 chips), then it is a non-ECC, non-parity module.
If you're building a PC and plan to use your system as a **server or a mission-critical machine**, it is to your advantage to use ECC memory. If you plan to use your PC for regular home, office, or gaming application, you are typically better off with non-ECC memory, as it is generally less expensive and may offer slightly higher speeds.

HOW TO TELL ECC, PARITY MEMORY FROM NON-ECC, NON- PARITY MEMORY?

If your system has ECC or parity memory, the main difference you will see is an extra memory chip (the 'ninth' chip in a bank of eight, or a 'data protection' chip). The total number of memory chips on the module will be evenly divisible by three (e.g., 9 chips on one side). Non-ECC modules usually have a number of chips that is a power of two (e.g., 8 or 16 chips total). For an exact match, DMS (Data Memory Systems) recommends using our memory finder tool or referencing the motherboard/system manual.

WHAT IS THE PERFORMANCE DIFFERENCE BETWEEN ECC, PARITY AND NON-ECC, NON-PARITY?

ECC (Error-Correcting Code) memory performs double-bit detection and single-bit correction. This means that if you have a single bit memory error, the chipset and memory will find and repair the error on the fly without you knowing that it happened. If you have a double-bit memory error, it will detect and report it. Non-ECC, non-parity memory, on the other hand, has no error detection and correction capabilities.
Using ECC can slightly decrease your PC's theoretical performance (typically a negligible amount) because of the extra clock cycle needed for error checking. Current technology DRAM is very stable and memory errors are rare, so unless you have a need for ECC (like in a server environment), you are often better served with non-ECC, non-parity memory for general use.

CAN I MIX AND MATCH ECC, PARITY AND NON-ECC, NON-PARITY?

When adding new memory, you must match what is already in your system and what your motherboard requires. **You should not mix ECC and Non-ECC modules.** Most motherboards that do not have an ECC function enabled in the BIOS are still able to use a module with ECC, but the module will run in non-ECC mode. However, a server or workstation motherboard that *requires* ECC will not function correctly with non-ECC memory. Always match the type that is already installed or required by the system for reliable operation.

WHAT DOES REGISTERED SDRAM MEAN? (UPDATED FOR DDR)

The term **Registered (or RDIMM)** refers to memory modules that contain a register chip. This chip buffers (delays) the control and address signals to the memory chips by one clock cycle. This buffering reduces the electrical load on the CPU’s memory controller, allowing servers and high-end workstations to support a much larger number of memory modules (and therefore, more total capacity) than Unregistered (or UDIMM) memory. This memory is primarily used in servers.
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CAN I MIX REGISTERED AND UNREGISTERED MEMORY?

**No.** Registered (RDIMM) and Unregistered (UDIMM) memory modules are **not interchangeable** and cannot be mixed in the same system. The motherboard's design is specifically wired to support one type or the other. Most standard PCs and laptops use Unregistered (Unbuffered) memory, while most high-capacity servers and workstations use Registered memory. You must match the type that is already installed or required by your system.

WHAT DOES BUFFERED MEMORY MEAN?

The terms Buffered and Registered are often used interchangeably, especially in the context of older memory, but they both refer to modules that contain extra chips (buffers/registers) to re-drive the signals to the memory chips. This allows for modules to be built with more chips and greater total capacity. Unbuffered (UDIMM) memory is the standard for consumer PCs, while Buffered/Registered (RDIMM) memory is used for high-capacity servers.

CAN I MIX BUFFERED AND UNBUFFERED MEMORY?

**No.** Buffered and Unbuffered modules are not interchangeable and cannot be mixed in the same system. They also use slightly different physical designs (notches) on the Printed Circuit Board (PCB). Trying to install the wrong type can physically prevent the module from seating correctly or, if forced, can damage the system.

WHAT ARE BUFFERED EDO AND FPM DIMMS? (OBSOLETE - SEE DDR INFO)

Buffered EDO (Extended Data Out) and FPM (Fast Page Mode) are older, obsolete memory types. Their concepts—using buffer logic to distribute the load placed on the chipset—have been carried forward into the Registered (RDIMM) memory used in modern servers and workstations utilizing DDR3, DDR4, and DDR5.

WHAT IS CAS LATENCY?

CAS Latency (Column Access Strobe Latency, often referred to as CL) is the amount of time it takes for your memory to respond to a command. Specifically, it is the length of time (measured in clock cycles) between the memory receiving a command to read data, and the first piece of data being output from the memory chip. Latency is noted as CL16, CL18, etc. (indicating 16 or 18 clock cycles). **Lower CL is generally better.**

PERFORMANCE DIFFERENCES BETWEEN DIFFERENT CAS LATENCIES

A lower CL rating (e.g., CL16) means the memory processes the initial request a little quicker than a higher CL rating (e.g., CL18) because it waits fewer clock cycles for the data. After the initial burst of data, the transfer rate is then determined by the memory's clock speed (MHz). While lower latency is desirable, the difference in everyday performance is often less noticeable than a jump in memory speed (MHz). When evaluating memory from DMS (Data Memory Systems), consider the balance between speed (MHz) and latency (CL) for optimal performance.

CAN DIFFERENT LATENCY PARTS BE MIXED?

CL parts with different latencies (e.g., CL16 and CL18) can generally be mixed. However, the system's BIOS settings should reflect the **highest (slowest) CL setting** of all the installed modules, as the faster module will run at the speed and timing of the slowest module installed to ensure stability.

HOW DIFFICULT IS IT TO INSTALL ADDITIONAL MEMORY?

Memory is one of the easiest of all system upgrades. Installing more memory usually involves simply removing the system cover (or accessing the laptop panel), ensuring you are grounded to prevent static discharge, and inserting the new modules into the empty memory slots. Then, replace the cover and power up the system. Most systems will recognize the increased memory automatically.

THE DIMM SLOT RETAINING CLIPS WILL NOT LOCK

The notches on the bottom of the memory module (where the gold leads are) should line up with the memory slot. Remember the socket is notched as well, so the module will only fit in one way for its generation (DDR3, DDR4, or DDR5). Each memory slot in your computer will have retaining clips on either side. As you push down *firmly* on the memory module with even pressure on both ends, these clips will automatically move up and lock into place. If you have to manually move the clips into place, then you are not pushing down hard enough on the memory module. Consistent, firm pressure (often 20–30 pounds) is typical until the clips click.

CAN YOU MIX AND MATCH MODULES OF DIFFERENT SIZES?

Different sizes of modules (e.g., 8GB and 16GB) can generally be mixed together, provided they are the same generation (DDR4 with DDR4) and have the same specifications (ECC/Non-ECC, Registered/Unregistered). For best performance, particularly with systems supporting **Dual Channel or Quad Channel** memory, DMS (Data Memory Systems) recommends installing matching pairs (or groups of four) of the **same size, speed, and timing** to ensure optimal performance.

DOES IT MATTER WHICH SLOTS THE MEMORY IS INSTALLED I?

**Yes, it matters a great deal.** Modern motherboards utilize Dual Channel, Triple Channel, or Quad Channel architectures to maximize data transfer. You must install modules in specific, color-coded slots (as indicated in your motherboard's manual) to enable these high-performance modes. For best results and performance, consult your motherboard manual to ensure the modules are installed in the correct slots to activate the optimal channel mode.

IF YOU GET AN ERROR MESSAGE "INVALID SYSTEM DISK"

After adding memory, if you get the error message, "Invalid system disk. Replace disk and press any key" and your system will not boot, this error message is consistent with a couple of problems. The most common is that when reaching to install your memory, you accidentally bumped a cable (perhaps a hard drive or SSD data/power cable). The first thing DMS (Data Memory Systems) suggests is to reseat all the cables in your computer, including the cables to the hard drive and hard drive power. The second much simpler solution may be that you have a non-bootable USB drive or a floppy disk (if applicable) in a drive.

YOU HAVE PLENTY OF RAM INSTALLED AND WINDOWS SAYS OUT OF MEMORY (UPDATED FOR MODERN SYSTEMS)

If you have 8GB or more of RAM and are still receiving 'Out of Memory' errors in modern operating systems (Windows 10/11 or macOS), it is unlikely to be a simple RAM limit. You may be running an excessive number of memory-intensive applications or have a software issue (a memory leak). Also, check your operating system's **Paging File** or **Virtual Memory** settings, as some system settings or applications may limit how much RAM they are allowed to use. Consult online resources for your specific operating system to adjust virtual memory settings, or use Task Manager/Activity Monitor to identify which application is consuming the most resources.