UDIMM Vs. DIMM: Know The Difference


Your computer uses information (or data) it stores (as memory) to function. Random-access memory (RAM) is a volatile short-term repository for working data.

There are several types of RAM. In this article, we shall focus on DIMM and UDIMM.  UDIMM is a memory module that stands for unbuffered/unregistered dual in-line memory, while DIMM represents dual in-line memory. 

In other words, UDIMM is a subset of DIMM. So, when we place them head to head, what do we get?


DIMM is a computer memory that enables fast data transfer and contains random access memory (RAM). DIMM is the most common memory module seen in computer systems today. Also called a RAM stick, DIMM comprises integrated dynamic random-access memory circuits (DRAM)

DIMM module mounts on the motherboard and stores information in different memory cells. DIMMs have 64 data bits with a standard length of 5.5 inches and a height of 1.18 inches. DIMM is present in many servers, desktops, laptops, workstations, and printers. 

UDIMM is the regular random access memory (RAM) and unbuffered DIMM. UDIMMs are affordable, and they offer a higher and faster performance rate.

UDIMM is a volatile type of computer memory chip that is primarily used in laptop and desktop computers. It is a conventional type of RAM. 

Since UDIMM is a type of RAM, it would help us know the other DIMM types and see how they hold up against UDIMM. But, first, let’s see how the concept of the DIMM emerged.

The DIMM Concept

Random-access memory is essential in data transfer. In addition, it functions in temporary data storage Improvements have been made to RAM technology to cater to the rising demand for faster data processing. 

These improvements replaced the single in-line memory module (SIMM) with the double in-line memory module (DIMM).

DIMMs became the most commonly used memory module as Intel P5-based premium processors began to gain market share. So, what are the different types of DIMM?

What Are The Different Types Of DIMM?

Unregistered DIMMs:

These are present mainly on personal computers. They don’t register or buffer on the motherboard as commands from the memory controller in the CPU go directly to the DRAM. They run fast, especially in systems with only one or two modules per memory channel. 

Registered DIMMs:

You can also refer to these as buffered memory. In RDIMMs, there are onboard memory registers placed between the dynamic random access memory (DRAM) modules and the memory controller. 

The onboard memory registers in RDIMMs electrically isolate the memory module from the rest of the motherboard. By doing so, it reduces the electrical load of the system.

Systems can populate with RDIMMs to boost memory capacity. In addition, systems or servers that require stability utilize RDIMMs.

Although RDIMMs and UDIMMs have the same memory, UDIMMs lack onboard buffering. However, RDIMMs increase efficiency in computers that use at least three modules per memory channel.

Fully buffered DIMMs:

These types of memory modules utilize advanced memory buffer chips to increase the dependability of memory systems. There is an arranged serial interface between the advanced memory buffer and the memory controller. 

The serial interface enables an increase in the memory width without leading to a substantial rise in the pin count of the memory controller. The reason is that the memory controller sends instructions to the memory register rather than the DRAM.

Therefore, the advanced memory buffer can correct errors and make up for signal deterioration without causing additional overhead on either the system’s memory controller or the processor. 

Small outline DIMMs:

The small outline dual in-line memory module is half the size of the standard DIMM (2.74 inches). It’s common in portable devices. 

Load-reduced DIMMs:

These types of memory modules use isolation memory buffer. The memory buffer reduces the electrical loading of the motherboard but does not affect the power draw. 

In LR- DIMMs servers, more modules can be put in each memory channel, thereby increasing the volume of system memory without causing a high latency tax.

You can’t mix different types of DIMMs in one server. Therefore, you should base your choice on its ability to deliver the suitable capacity needed for optimum server performance. Speaking of optimum server performance, how fast is the DIMM in handling data?

About DIMM Speeds

Memory access speeds vary for different technologies. Faster speeds lead to quick processing of queued commands. The quicker the DIMM speed, the lower the latency rate.

There are two types of DIMM with regards to speed – single data rate (SDR) and double data rate (DDR) DIMMs with Single Data Rate (SDR) DRAM have the same clock cycle for internal and bus clocks. Therefore, the bus frequency for data, control lines, and address are the same.

DIMMs that use the Double Data Rate (DDR) have their data double the clock rate. There are four generations of DIMM and DDR: DDR, DDR2, DDR3, and DDR4.

Architecture Of DIMM

DIMMs are printed motherboards integrated with DRAM and SDRAM. They come with a 64-bit data plan using the “four” or by “eight” (“x4” or “x8”) memory chips. The density of the chip is critical because it enhances performance standards.

The increase from 32GB (used in the predecessor memory module) to 64GB led to increased heat production. Consequently, manufacturers produced cooling fans to vent the excess heat produced through the exit way of computers.

Presently, you’ll find DIMM RAM chips located on either one or both sides of the motherboard. However, sometimes, DIMM RAM chips may share the same slot. We call these DIMM ranks.

What Are DIMM Ranks?

Ranks are two or more independent sets of DIMM chips connected to the same data buses and address. As such, they share the same slot. 

You can only access DIMM ranks one at a time. Accessing a given DIMM rank occurs by activating the corresponding rank’s chip select (CS) signal.

Similarly, to deactivate ranks on the module during the operation of the activated DIMM rank, their corresponding chip select signals will deactivate. Loaded latency of DIMM improves with an increase in channel ranks. And the higher the rank speed the greater the ability to process memory requests.

Given that DIMMs are the successor to SIMMS, what advantages do they offer?

Advantages Of DIMM

  • They can store twice the data of a SIMM because they have separate individual contacts on both sides of the motherboard.
  • The DIMM stores contacts and addresses before sending them out. As a result, this helps reduce the load on the memory.

So, with these advantages in mind, how long do DIMMs last? Do they ever need replacement? 

When Should You Replace A DIMM?

Although most DIMMs can last for a computer’s entire lifetime, certain situations where they need replacement may arise.

DIMMs are prone to memory errors. You can fix some memory errors and get your system working smoothly again. However, you can’t fix some errors. We refer to them as Uncorrectable Memory Errors.

A DIMM needs replacement when it does not agree with the BIOS memory test due to Uncorrectable Memory Errors (UCEs).

Future Of DIMM

DIMM and DDR have had four generations – DDR, DDR2, DDR3, and DDR4, but we now have a 5th – DDR5.

Ever since the JEDEC standards organization released the specification for DDR5 in 2018, manufacturers have started creating the DDR5. DDR5 is a successor of DDR4, and for now, it is only compatible with Intel’s Alder Lake 12th generation desktop processor.

It offers twice the transfer rate of DDR4, which has 25 GBs. It has been given an architectural boost and a higher performance rate of 1.8 times more than DDR4.

It begins with a performance rate of 4,800 MHZ to 5,600 MHZ, and it uses less power than the DDR4.

While the DDR4 has its highest capacity of 32GB per stick, DDR5 quadruples that figure as it can offer up to 128GB RAM sticks.

Although the DDR5 is only working on Intel’s 12the generation desktop processor, for now, AMD intends to produce compatible chips with the DDR5 by 2022.

How To Troubleshoot For DIMM Errors

Like we mentioned earlier, some memory errors are fixable. However, most times, the problem may be from the hardware. Here’s how you can isolate and fix DIMM memory errors.

  • Shut down your server to standby power, and then open it.
  • Be sure to check the DIMM to know if it complies with the DIMM population rules as written in your product service manual.
  • Next, critically check the DIMM fault LEDs by pressing the Remind button.
  • Detach the AC power cords from the server and then remove the DIMM from its slot.
  • Check the DIMM connectors for dust or any form of contamination. Also, look out for any damage or a crack in the DIMM slot.
  • If there is dirt anywhere, clean them off carefully. If it is a case of it being damaged, replace it with a new one.
  • Reconnect the AC power cords back into the server and then put them on the server again. Rerun a test.
  • Recheck the log files.

Note: If the errors still exist, the problem is from the CPU and not the DIMM.


UDIMM stands for unbuffered/ unregistered dual in-line memory, while DIMM represents dual in-line memory. DIMM is a computer memory that enables fast data transfer and can contain more than one RAM chip. 

UDIMM is a volatile computer memory chip that is primarily used in laptop and desktop computers. UDIMM is a type of DIMM. It is a conventional random access memory (RAM) and unbuffered/ unregistered DIMM.

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