Four module names cause most of the confusion in desktop and laptop memory: SODIMM, CSODIMM, UDIMM and CUDIMM. Two describe size and two add a clock driver to DDR5. Here is what each one is, how they differ, and how to know what your computer takes.
The short answer
- SODIMM and UDIMM are the standard modules. SODIMM is the compact size used in laptops and mini PCs, and UDIMM is the full size used in desktops and workstations.
- CSODIMM and CUDIMM are the same two sizes in DDR5 with a clock driver added to the module. The driver cleans up the clock signal so memory can run reliably at higher speeds.
- None of the four is server memory. All four are unbuffered. RDIMM and LRDIMM are the registered types that servers use.
NEMIX RAM supplies SODIMM and UDIMM in DDR5, DDR4 and DDR3, including the ECC versions. We do not currently offer CSODIMM or CUDIMM modules, so this guide is here to help you tell whether your system needs them.
SODIMM, CSODIMM, UDIMM and CUDIMM side by side
| SODIMM | CSODIMM | UDIMM | CUDIMM | |
|---|---|---|---|---|
| Full name | Small Outline DIMM | Clocked Small Outline DIMM | Unbuffered DIMM | Clocked Unbuffered DIMM |
| Size | Compact | Compact | Full size | Full size |
| Where it is used | Laptops, mini PCs, NUCs, all in one PCs, many NAS units | Compact systems whose platform supports clock drivers | Desktops, workstations, industrial ATX boards | Desktops whose platform supports clock drivers |
| Memory generation | DDR3, DDR4, DDR5 | DDR5 only | DDR3, DDR4, DDR5 | DDR5 only |
| Pins on DDR5 | 262 | 262 | 288 | 288 |
| Clock driver on the module | No | Yes | No | Yes |
| Buffered or registered | No | No | No | No |
| JEDEC standard | Yes | JESD324 | Yes | JESD323 |
| Needs platform support for the clock driver | No | Yes | No | Yes |
What the clock driver does
On an ordinary DDR5 module, the clock signal travels from the processor straight to the memory chips. As speeds rise, that signal degrades. A clocked module places a small clock driver on the module itself. It regenerates the clock locally, which improves signal quality and helps the module stay stable at higher data rates. JEDEC, the industry standards body, published the two designs as JESD323 for CUDIMM and JESD324 for CSODIMM. The first version covers 6,400 to 7,200 MT/s, with later versions aimed at up to 9,200 MT/s.
The clock driver is not a register. It does not buffer commands or data, and it does not turn a CUDIMM into server memory. A CUDIMM is still unbuffered memory that fits a desktop board.
Pair one: SODIMM and CSODIMM
SODIMM is the compact module found in laptops, mini PCs, NUCs, all in one computers and many NAS units. It comes in DDR3, DDR4 and DDR5. A DDR5 SODIMM has 262 pins and a DDR4 SODIMM has 260. Browse DDR5 SODIMM, DDR4 SODIMM or all laptop memory.
CSODIMM is the same size and pin count in DDR5 only, with a clock driver. It targets compact systems that need higher memory speeds. Intel lists CSODIMM support at DDR5-6400 on Arrow Lake, but only on platforms whose maker built for it. A system designed around an ordinary SODIMM will not necessarily take a CSODIMM.
Pair two: UDIMM and CUDIMM
UDIMM is the standard full size module for desktops, workstations and industrial ATX boards. It comes in DDR3, DDR4 and DDR5, and DDR4 and DDR5 versions have 288 pins. Browse DDR5 UDIMM, DDR4 UDIMM or all desktop memory.
CUDIMM is the full size DDR5 module with a clock driver. It is aimed at enthusiast and high speed desktops. Retail kits are sold at 6,400 MT/s and well above, and a CUDIMM needs a board and processor that support it to run at its rated speed.
What speeds each one reaches
Rated speed on the label is a ceiling, not a promise. What a system actually runs depends on the processor, the board, the BIOS and how many modules are installed. Intel and AMD handle clocked modules differently:
| Module | Intel Core Ultra 200S (Arrow Lake) | AMD Ryzen 7000, 8000G and 9000 on AM5 |
|---|---|---|
| Regular DDR5 UDIMM or SODIMM | DDR5-5600 officially | Set by the board, the BIOS and the kit profile |
| DDR5 CUDIMM, one module per channel | DDR5-6400 native, DDR5-7200 on Arrow Lake Refresh | Runs in bypass mode, about 6000 MT/s, on supported AM5 boards |
| DDR5 CUDIMM, two modules per channel | DDR5-4800 for single rank, DDR5-4400 for dual rank | Platform dependent |
| DDR5 CSODIMM | DDR5-6400 on Arrow Lake | Check the laptop maker, support is not general |
Intel built native CUDIMM support into Arrow Lake, so a CUDIMM runs with its clock driver active. AMD does not yet support the clock driver natively on Ryzen 7000, 8000G and 9000. A newer BIOS lets the board accept the module, and the module runs in bypass mode, behaving like an ordinary UDIMM at a lower speed. AMD is reported to be planning native support for a future generation. These platform details change with every BIOS and processor launch, so confirm against your board maker's current memory support list.
Will a clocked module work in my computer?
A CUDIMM has the same 288 pins and the same size as a DDR5 UDIMM, and a CSODIMM matches a DDR5 SODIMM. Physically fitting is not the same as being supported. A board that does not know about clock drivers may refuse the module, or may run it as an ordinary module at a slower speed, depending on the BIOS. Use only the module types your board maker or laptop maker lists for that exact model.
The reverse is simpler. An ordinary DDR5 UDIMM or SODIMM works in every board and laptop designed for DDR5, at the speed that platform supports. For most buyers that is the right choice, and it is what our DDR5 modules are matched to.
ECC, a separate question
DDR5 memory has error correction built into each chip, called on-die ECC, and that is not the same as an ECC module. An ECC UDIMM or ECC SODIMM adds extra bits across the module, and only boards that support ECC use them. We supply those separately. See DDR5 ECC UDIMM and DDR5 ECC SODIMM for modules matched to workstations, industrial PCs and NAS systems that list ECC.
Which type fits which system
| System | Usual module | Note |
|---|---|---|
| Laptops, NUCs and mini PCs | DDR4 or DDR5 SODIMM | Confirm DDR4 or DDR5 first, since the two do not interchange. |
| NAS units and compact industrial PCs | SODIMM, ECC SODIMM where listed | Use the type the maker lists. |
| Desktops and industrial ATX boards | DDR4 or DDR5 UDIMM | Match the speed your processor supports. |
| Workstations with ECC | ECC UDIMM | The board and processor must support ECC. |
| High speed gaming desktops | DDR5 UDIMM or CUDIMM | CUDIMM only on a board and processor that support it. |
| Servers | RDIMM or LRDIMM | None of the four types above. |
For compact systems see our NUC and mini PC memory guide and SODIMM memory guide for laptops, mini PCs and NAS. For desktops see the gaming PC and laptop memory guide and motherboard RAM by chipset guide.
How to check what your system takes
- Find the exact model of the laptop, mini PC or motherboard, and the processor.
- Confirm DDR4 or DDR5. The generations are not interchangeable.
- Read the maker's memory specification for the module type. It will say SODIMM, UDIMM, or a clocked type such as CUDIMM or CSODIMM.
- Note the speed per channel. Boards run slower when more than one module sits on a channel.
- Send us the model and we will confirm the module. Our memory by manufacturer and memory by specification pages start the search for you.
Frequently asked questions
What is the difference between UDIMM and CUDIMM?
Both are full size unbuffered desktop modules. A CUDIMM is DDR5 only and adds a clock driver that regenerates the clock signal on the module, which helps it stay stable at higher speeds. A UDIMM has no clock driver and comes in DDR3, DDR4 and DDR5.
What is the difference between SODIMM and CSODIMM?
They are the same compact size. A CSODIMM is DDR5 only and has a clock driver. A SODIMM has none and comes in DDR3, DDR4 and DDR5.
Can I use a CUDIMM in a regular DDR5 motherboard?
It depends on the board and BIOS. The module fits the same slot as a DDR5 UDIMM, but a board without clock driver support may not run it, or may run it as an ordinary module at a lower speed. Check your board maker's memory support list for the exact module.
Do AMD Ryzen processors support CUDIMM?
Ryzen 7000, 8000G and 9000 can accept CUDIMM with a supporting BIOS, but they run it in bypass mode at roughly 6,000 MT/s, not with the clock driver active. Intel Core Ultra 200S supports CUDIMM natively.
Is CUDIMM server memory?
No. CUDIMM is unbuffered desktop memory. Servers use registered memory such as RDIMM and LRDIMM, which a desktop board will not accept.
Does NEMIX RAM sell CUDIMM or CSODIMM?
Not at this time. We supply DDR5, DDR4 and DDR3 SODIMM and UDIMM, including ECC SODIMM and ECC UDIMM, matched to the systems that list them. If your system lists an ordinary SODIMM or UDIMM, we can match it.
Sources
JEDEC on DDR5 clock drivers, CUDIMM and CSODIMM, Tom's Hardware on Intel Arrow Lake Refresh CUDIMM support and Tom's Hardware on AMD EXPO 1.2 and CUDIMM bypass mode, read on October 28, 2026. Specifications and platform support change as new processors and BIOS versions launch, so confirm against the current maker documentation.
Related guide: CAMM2 vs LPCAMM2: what the new laptop memory modules are and which systems use them
Buying memory for desktops, mini PCs and fleets
NEMIX RAM is a US-based memory specialist, in business since 1993. Every module is researched, matched, and compatibility-tested by NEMIX RAM, is JEDEC-compliant, and is backed by a lifetime warranty. Purchase orders, net terms and volume pricing are available for business, reseller and public-sector orders. Request a quote with your models and quantities, or contact our sales team.
NEMIX RAM is an independent memory supplier and is not affiliated with the companies named here. Intel, Core Ultra, Arrow Lake, AMD, Ryzen, EXPO and JEDEC are trademarks of their respective owners, used here only to identify compatible systems.