Guide updated November 2026. Availability is confirmed per part number when you request a quote.
DDR4 or DDR5 — the server decides, not the buyer
The most common purchasing error in server memory is ordering the right capacity in the wrong generation. The two are not interchangeable: the edge connector is keyed differently and the platform is built for one or the other. Match the memory to the server model first, then choose capacity and speed.
| Platform generation | Memory | Typical speeds | Channels |
|---|---|---|---|
| HPE ProLiant Gen10 Plus, Dell PowerEdge R650 / R750, LGA4189 | DDR4 RDIMM | 2933 / 3200 MT/s | 8 channels per socket |
| HPE ProLiant Gen11, Dell PowerEdge R660 / R760, LGA4677 (4th and 5th Gen Xeon) | DDR5 RDIMM | 4800 / 5600 MT/s | 8 channels per socket |
| Xeon 6 platforms (LGA4710) | DDR5 RDIMM | up to 6400 MT/s | 8 channels per socket |
| Entry 1U servers, Xeon E-2400 (LGA1700) | DDR5 ECC UDIMM | 4800 MT/s | 2 channels per socket |
If you are unsure, send the server model and we confirm the memory generation and the supported speed bins before quoting.
DDR4 vs DDR5 — full specification comparison
| Specification | DDR4 RDIMM | DDR5 RDIMM |
|---|---|---|
| Operating voltage | 1.2 V | 1.1 V, with an on-module power management IC (PMIC) |
| Speed on current server platforms | 2133 to 3200 MT/s | 4800 to 5600 MT/s (up to 6400 on Xeon 6) |
| Channel architecture | One 64-bit channel per DIMM | Two independent 32-bit sub-channels per DIMM |
| Typical capacities in supply | 16 / 32 / 64 GB | 16 / 32 GB |
| Label prefix | PC4 | PC5 |
| Edge connector keying | Notch at the DDR4 position only | Notch shifted — will not fit a DDR4 slot |
| Typical platforms | HPE Gen10 / Gen10 Plus, Dell R640 to R750, AMD EPYC 7002 / 7003 | HPE Gen11, Dell R660 / R760, AMD EPYC 9004, Xeon 6 |
| Interchangeable with the other generation | No | No |
Server RAM prices — what actually moves the unit price
Four factors set the price of a module, in rough order of impact:
- Density per module — a 64 GB module carries more value than a 16 GB module, but the price per gigabyte usually falls as density rises, which is why consolidating into fewer, larger modules is the cheaper route.
- Generation — DDR5 modules price well above DDR4 at the same capacity because the chips are denser and the platforms they fit are newer.
- Speed bin — within one generation, the higher speed grades (DDR4-3200, DDR5-5600) carry a premium over entry bins of the same capacity.
- Rank count and batch matching — dual-rank and quad-rank modules and batch-matched sets affect the quote, which is why we quote per part number rather than per gigabyte.
Indicative ranges for the listings on this page: DDR4 RDIMM $60 to $600 per unit, DDR5 RDIMM $300 to $950 per unit. Every order is quoted per part number for the confirmed quantity and destination, and the quote is valid the day it is issued.
Which server models take which generation
For the server platforms we list on zhongxindata.hk, the memory mapping is fixed:
| Memory generation | Server models we list | Memory listing |
|---|---|---|
|
DDR4 RDIMM 2133 to 3200 MT/s |
Dell PowerEdge R640, R650, R650xs, R740, R750xa, R7525; HPE ProLiant DL380 Gen10, DL385 Gen10 Plus | DDR4 RDIMM 16 / 32 / 64 GB |
|
DDR5 RDIMM 4800 to 5600 MT/s |
Dell PowerEdge R660 / R760 class (4th and 5th Gen Xeon, LGA4677); HPE ProLiant Gen11 | DDR5 RDIMM 16 / 32 GB |
Pair the modules with a tested chassis from Servers & Barebones, or see all memory listings. If your platform is not in the table, send the model and we confirm the generation and speed bins before quoting.
Desktop RAM vs server RAM — why the two are not interchangeable
Searches often land buyers on desktop-grade DDR4 or DDR5 because the sticker speeds look similar. The parts differ in three ways that matter for a server:
- Buffering — server RDIMMs carry a register and buffer that let a memory controller drive high capacities across eight channels. Desktop UDIMMs are unbuffered and will not post in a slot that expects RDIMM.
- ECC — enterprise modules correct single-bit errors in hardware, which is what a server platform is designed around. Consumer modules typically lack functional ECC.
- Capacity per module — high-density server modules reach 64 GB and above per stick, well past the usual desktop range, and that density is what fills eight channels economically.
RDIMM, UDIMM and LRDIMM — which one fits a server
| Type | Buffering | Where it belongs | What it means in practice |
|---|---|---|---|
| RDIMM | Registered, buffered | Rack and tower servers with Xeon Scalable | The default for enterprise servers. The register and buffer reduce electrical load, which is what makes high capacity per channel possible. |
| UDIMM | Unbuffered, ECC or non-ECC | Entry servers, workstations, Xeon E-2400 | Cheaper and lower latency per module, but limited capacity and channel count. Not interchangeable with RDIMM on the same board. |
| LRDIMM | Load-reduced, buffered | Maximum capacity per channel | Uses a buffer chip to cut load further. Only worth it when you need the highest capacity per slot, and the platform must support it. |
RDIMM and UDIMM cannot be mixed on the same board. If a listing does not state the type, ask before ordering — a UDIMM in a RDIMM slot will not post.
Server memory listed on zhongxindata.hk
| Generation | Capacities | Speeds | Type | Indicative range (USD/unit) | Listing |
|---|---|---|---|---|---|
| DDR5 RDIMM | 16 GB / 32 GB | 4800 / 5200 / 5600 MT/s | ECC, registered | $300 – $950 | View listing |
| DDR4 RDIMM | 16 GB / 32 GB / 64 GB | 2133 / 2400 / 2666 / 2933 / 3200 MT/s | ECC, registered | $60 – $600 | View listing |
Availability: the module capacities listed on this page are in stock. Availability is confirmed per part number when you request a quote.
Mixing rules buyers ask about
- Same generation, different capacity — works. Every module then runs at the lowest common speed of the set, so a single slower module slows the whole bank.
- Different number of ranks — usually works, but check the platform population guide; mixing ranks can force a lower speed.
- Two DIMMs per channel (2DPC) — supported on most platforms but normally costs one to two speed bins. If bandwidth matters, one DIMM per channel at the rated speed often beats two at a reduced speed.
- DDR4 with DDR5 — never. Different keying, different voltage, different platform.
- RDIMM with UDIMM — never, on the same board.
- Unpopulated channels — the most common and most invisible loss. Eight channels exist so you can use them; two DIMMs per socket leaves bandwidth on the table.
How to check what you actually received
- Label prefix — PC4 means DDR4 and PC5 means DDR5. A DDR4 module in a DDR5 order is visible on the label before you open anything.
- Part number decode — the module part number carries density, rank, speed and voltage. Match it against the order line, not just against the capacity printed on the sticker.
- Register and buffer present — a genuine RDIMM has the register and buffer components on the board. Their absence is the tell for a UDIMM relabelled as RDIMM.
- Batch consistency — for a matched build, confirm the part numbers and date codes are consistent across the set.
- Post and burn-in — every module is fitted to a matching platform and must post and pass a memory test before it ships.
Capacity planning in one paragraph
Work backwards from the workload, not from the maximum the board accepts. Virtualization hosts generally want 4 to 8 GB per vCPU after the hypervisor reserve; in-memory databases want enough to hold the working set with headroom, which usually means filling every channel with the largest module the budget allows; and a build that will be expanded later is better started with fewer, larger modules than with all slots half-filled. Pair memory with processors matched to the same socket generation, or check the chassis in Servers & Barebones.
Frequently asked questions
What is the difference between DDR4 and DDR5 server memory?
DDR4 RDIMM runs at 1.2V and tops out around 3200 MT/s on current server platforms. DDR5 RDIMM runs at 1.1V, carries a power management chip on the module itself and splits each module into two 32-bit sub-channels, which is where the higher bandwidth comes from. They are not interchangeable.
Can I mix DDR4 and DDR5 in the same server?
No. The two generations are keyed differently and run at different voltages, and a given platform supports one generation only. Check the server model before ordering — Gen10 Plus and R650 / R750 take DDR4, Gen11 and R660 / R760 take DDR5.
Can I mix different capacities in the same server?
Yes, within the same generation and module type. All modules then run at the lowest common speed, and an unbalanced population costs you bandwidth. Populate every channel before adding a second DIMM to a channel.
What is the difference between RDIMM and UDIMM?
RDIMM is registered and buffered, which is what enterprise rack servers use. UDIMM is unbuffered, used in entry servers and workstations. They cannot be mixed on the same board, and a UDIMM will not work in a slot that expects RDIMM.
How do I tell DDR4 from DDR5 by looking at the module?
The label prefix is the quickest check: PC4 is DDR4 and PC5 is DDR5. Physically, the notch on the edge connector sits in a different position, and a DDR5 module has a small power management chip on the board.
Do you supply matched kits?
We quote per part number and confirm the configuration before shipping. If you need a matched set of identical part numbers and batches for a build, state that in the quote request and we confirm what we can supply.
Does used server memory come with a warranty?
Every module we ship carries a 90-day warranty from delivery, covering hardware defects.
What capacities and speeds do you list?
DDR5 RDIMM in 16 GB and 32 GB at 4800 to 5600 MT/s, and DDR4 RDIMM in 16 GB, 32 GB and 64 GB at 2133 to 3200 MT/s. Other capacities are quoted per part number on request.
Can I order memory in volume?
Yes. Volume tiers start at 10 units for most part numbers. Send the part number and quantity on WhatsApp and the quote is issued for that quantity and destination.
Where do you ship from?
From Hong Kong, China, with the carrier and destination agreed in the quote.
Can I use desktop RAM in a server?
In practice, no. Desktop modules are unbuffered UDIMMs, usually non-ECC, and a server board that expects RDIMM will normally fail to post with one installed. Server platforms also need the capacity density and ECC behaviour that RDIMM provides, which is why we list ECC RDIMM only.
How much does server memory cost per unit?
Price scales with density per module, speed bin and generation. As a guide, our used DDR4 RDIMM listings run $60 to $600 per unit and DDR5 RDIMM $300 to $950 per unit. A single 64 GB module usually prices below the equivalent capacity in four 16 GB modules, so filling channels with larger modules is normally the cheaper route per gigabyte. The final quote depends on the exact part number, quantity and destination.
Is used server memory reliable?
Enterprise RDIMM is specified for 24/7 operation with ECC error correction, and modules pulled from decommissioned servers have already been through their highest-stress years. What matters is the re-test: every module we ship is fitted to a matching platform, must post and pass a memory test on our own bench, and carries a 90-day warranty from delivery.
What does PC4-25600 or PC5-44800 on the label mean?
The prefix identifies the generation — PC4 is DDR4 and PC5 is DDR5. The number that follows is the peak bandwidth in MB/s, which is the transfer rate times eight: PC4-25600 corresponds to DDR4-3200 and PC5-44800 corresponds to DDR5-5600. Match the decoded speed bin against your platform's supported speeds, not just the sticker capacity.
Do I need HPE or Dell branded memory?
No. The modules inside branded kits come from the same small group of DRAM makers, qualified across platforms. What matters is the generation, the speed bin and the platform population rules — a correctly specified third-party RDIMM posts and runs the same as the branded part in the same slot.
How many DIMMs can I install per channel?
Most Xeon Scalable and EPYC platforms support one DIMM per channel at full rated speed, and two per channel at a one to two speed bin penalty. Populate every channel first before adding a second DIMM to any channel, and follow the platform's population order — it is printed in the server's quick specs or owner's manual.
Request a memory quote
Send the server model, the capacity and speed you need, and the quantity on WhatsApp +86 13068616914. We confirm the generation and speed bins against your platform, then issue a quote valid the day it is issued.