DDR3
What Is DDR3 Memory?
DDR3 stands for Double Data Rate 3 Synchronous Dynamic Random-Access Memory, commonly abbreviated DDR3 SDRAM. It is the generation of system memory that succeeded DDR2 and preceded DDR4.
DDR3 was widely used in desktops, workstations and enterprise servers. Server implementations commonly include ECC-capable DDR3 memory in registered and, on supported platforms, load-reduced configurations.
DDR3 Memory at a Glance
DDR3 represents a specific memory generation. Identifying a module as DDR3 alone does not establish its capacity, speed, ECC capability, rank or DIMM architecture.
Third-Generation DDR
DDR3 followed DDR2 and was later succeeded by DDR4.
Lower Voltage Than DDR2
Standard DDR3 commonly operates at 1.5 V, while DDR3L supports lower-voltage operation at 1.35 V on compatible systems.
Extensive Server Use
DDR3 was widely deployed across enterprise server generations from major system manufacturers.
Platform-Specific
DDR3 cannot be selected by capacity and speed alone. DIMM type, ECC support, rank and platform requirements also matter.
How Does DDR3 Memory Work?
DDR3 is a form of synchronous DRAM. “Double Data Rate” refers to transferring data on both edges of the memory clock signal, allowing multiple data transfers during each clock cycle. The processor's memory controller communicates with DDR3 modules through the platform's memory channels.
Common DDR3 Memory Speeds
DDR3 modules are available at several transfer rates. The effective operating speed depends on the processor, motherboard or server, DIMM type and memory population.
| DDR3 Designation | Transfer Rate | PC Rating | General Context |
|---|---|---|---|
| DDR3-800 | 800 MT/s | PC3-6400 | Earlier DDR3 platforms |
| DDR3-1066 | 1066 MT/s | PC3-8500 | Common older server and workstation speed |
| DDR3-1333 | 1333 MT/s | PC3-10600 / PC3-10666 | Widely used DDR3 generation speed |
| DDR3-1600 | 1600 MT/s | PC3-12800 | Common later DDR3 server and workstation speed |
| DDR3-1866 | 1866 MT/s | PC3-14900 | Later high-speed DDR3 platforms |
Note: Naming conventions and rounded PC ratings can vary by manufacturer. Always use the exact server and memory specifications when determining compatibility.
What Does PC3 Mean?
PC3 identifies DDR3 memory in a bandwidth-oriented naming convention. For example, DDR3-1600 is commonly associated with PC3-12800. The DDR3 designation expresses the transfer rate, while the PC3 rating represents approximate theoretical bandwidth in MB/s.
Server memory labels may contain additional letters that identify characteristics such as ECC, registered operation, load-reduced architecture or voltage. The complete part number and specification should therefore be used when selecting replacement memory.
DDR3 vs DDR3L: What Is the Difference?
Standard DDR3 is commonly associated with 1.5 V operation. DDR3L is a low-voltage DDR3 specification designed for 1.35 V operation. Depending on the module and platform, some DDR3L memory can support operation at more than one voltage, but compatibility should never be assumed solely because the DIMM physically fits.
When replacing server memory, verify whether the system specifies DDR3, DDR3L or another supported voltage configuration and match the manufacturer's memory population requirements.
Types of DDR3 Server Memory
DDR3 describes the memory generation—not the complete DIMM architecture. Enterprise DDR3 platforms can use different DIMM types depending on the server and processor.
DDR3 UDIMM
Unbuffered DDR3 memory is used in desktops, workstations and certain server platforms. Both ECC and non-ECC implementations exist.
Learn About UDIMM →DDR3 RDIMM
Registered DDR3 DIMMs were extensively used in enterprise servers requiring reliable and scalable memory configurations.
Learn About RDIMM →DDR3 LRDIMM
Supported memory-dense enterprise platforms can use load-reduced DDR3 DIMMs to reduce electrical loading and support large memory configurations.
Learn About LRDIMM →What Is DDR3 ECC Memory?
DDR3 ECC memory is DDR3 memory used in an ECC-capable memory subsystem. ECC, or Error-Correcting Code, provides mechanisms designed to detect and correct certain memory errors when supported by the processor, motherboard and system configuration.
ECC does not identify whether a DDR3 DIMM is registered, unbuffered or load-reduced. For example, a server may use DDR3 ECC RDIMMs while another compatible system may require DDR3 ECC UDIMMs.
DDR3 vs DDR4: Key Differences
DDR4 succeeded DDR3 with a newer memory architecture, increased transfer rates and different electrical and physical specifications.
| Characteristic | DDR3 | DDR4 |
|---|---|---|
| Generation | Third-generation DDR | Fourth-generation DDR |
| Standard Voltage | Typically 1.5 V | Typically 1.2 V |
| Typical Transfer Rates | Lower than DDR4 generation | Higher than DDR3 generation |
| Physical Compatibility | DDR3-specific DIMM slot | DDR4-specific DIMM slot |
| Interchangeable? | No | No |
Can DDR3 and DDR4 Memory Be Interchanged?
No. DDR3 and DDR4 are different memory generations and should not be treated as interchangeable. They use different electrical specifications and physical DIMM designs. A DDR3 server requires the DDR3 memory types supported by that specific platform.
A newer memory generation cannot simply be substituted for DDR3 because it offers higher performance. Upgrading from DDR3 to DDR4 normally requires a platform designed for DDR4 memory.
How Do You Identify DDR3 Server Memory?
The safest method is to identify the exact memory part number and compare its complete specifications with the server's supported memory configuration.
DDR3 Server Memory Compatibility
Two DDR3 DIMMs can share the same capacity and transfer rate while still being incompatible with the same server. Enterprise memory compatibility depends on the processor, motherboard, memory controller, DIMM architecture, ECC support, rank, voltage, population and server firmware.
When upgrading a DDR3 server, identify the exact server model, processor configuration and currently installed memory before selecting replacement or expansion DIMMs.
Can Different DDR3 DIMMs Be Mixed?
Do not assume that all DDR3 modules can be mixed simply because they belong to the same memory generation. Server manufacturers define supported combinations of DIMM type, capacity, rank, speed and memory population.
Mixing registered, unbuffered and load-reduced memory is particularly dependent on platform rules. A server may support multiple DIMM architectures as separate configurations without supporting them simultaneously.
What to Check Before Buying DDR3 Server Memory
DDR3 Memory FAQ
What does DDR3 stand for?
DDR3 stands for Double Data Rate 3 and refers to the third generation of DDR SDRAM.
What is PC3 memory?
PC3 is a naming convention used with DDR3 memory that expresses approximate theoretical memory bandwidth.
Is DDR3 still used?
Yes. DDR3 remains in service in many legacy servers, workstations and computer systems that continue to perform useful production roles.
Is DDR3 server memory ECC?
Many enterprise DDR3 server configurations use ECC memory, but DDR3 itself does not mean ECC. Both ECC and non-ECC DDR3 memory exist.
Is DDR3 the same as DDR3L?
DDR3L is a low-voltage DDR3 specification associated with 1.35 V operation. Compatibility depends on the module and platform.
Can DDR3 and DDR4 be mixed?
No. DDR3 and DDR4 are different memory generations with different physical and electrical specifications.
Can DDR4 replace DDR3?
Not in a DDR3-only system. Moving to DDR4 requires a platform designed to support DDR4 memory.
What is DDR3 RDIMM?
A DDR3 RDIMM is a registered DIMM using DDR3 memory technology. RDIMMs were widely deployed in enterprise servers.
How do I know which DDR3 RAM I need?
Identify the system model, processor, DIMM type, ECC requirement, capacity, speed, rank, voltage and existing memory configuration before selecting a module.