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 varies by configuration and volumeto varies by configuration and volumeper unit, DDR5 RDIMM varies by configuration and volumeto varies by configuration and volumeper 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 | Quoted | View listing |
| DDR4 RDIMM | 16 GB / 32 GB / 64 GB | 2133 / 2400 / 2666 / 2933 / 3200 MT/s | ECC, registered | Quoted | View listing |
Availability: the module capacities listed on this page are quoted per part number. 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.
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.
Request a Quote on WhatsApp +86 13068616914
DDR4 and DDR5 enterprise RDIMM we supply
- DDR4 RDIMM for HPE Gen9, Dell 12th-generation and earlier platforms
- DDR5 RDIMM for Gen10, Dell 13th-generation and newer platforms, rated at 4800 through 5600
- LRDIMM where the platform supports it, for higher capacity per socket
Matching a memory kit to your server before you order
- Generation and module type must both match — DDR4 does not fit a DDR5 slot
- Check the maximum capacity per slot and per socket for the exact platform
- Populate channels symmetrically, because an unbalanced set leaves bandwidth unused
How we test memory, and why we test the set
- The full set is stress-tested together rather than module by module
- That is what surfaces uncorrectable errors and marginal modules that pass a quick boot
- We confirm the part number, the speed rating and the capacity per module, and state the tested configuration
Why buyers choose used memory for expansion
- The cost difference against current-generation modules is largest on older platforms
- Used memory is a strong fit for capacity expansion, test environments and refresh cycles
- The condition of each unit is stated in the quote and every set is tested on our own line
Related reading
- DDR5 enterprise RDIMM — the DDR5 side of the offer
- DDR4 enterprise RDIMM — the DDR4 side of the offer
- Server memory guide — the selection detail
- Server memory — category hub
Frequently Asked Questions
Can I use DDR4 memory in a DDR5 server?
No. The generations are physically incompatible — DDR5 uses a different keying and pin count, so DDR4 modules will not fit DDR5 slots and vice versa. Check the platform generation before you order, and we will confirm the exact modules for your server model.
Do I need ECC RDIMM or LRDIMM for a server?
ECC RDIMM is the normal server configuration, and most server platforms require ECC. LRDIMM adds a data buffer, allowing higher capacity per module and higher supported speeds, but it needs platform support — so confirm your CPU and board before ordering. Our memory guide explains the distinction in full.
How much memory can I install in my server?
That depends on the platform’s maximum per slot and per socket, and on whether it supports LRDIMM. Give us the server model and we will confirm the supported configurations and the population pattern that gives you full memory bandwidth.
How do you verify used server memory?
We stress-test the full set together on our own test line, which surfaces uncorrectable errors and marginal modules that a quick boot would miss. We confirm the part number, the speed rating and the capacity per module, and we state the exact configuration that was tested in the quote.
Why do my DDR5 modules run slower than rated?
Two causes cover almost every case. A mixed set runs at the speed of the slowest module, and the platform applies a speed-versus-capacity curve, so a larger module can be rated lower. Both are normal behaviour rather than a fault, and both are worth checking before you order additional modules.
What warranty applies to used server memory?
90-day warranty from delivery on every module, with the set tested before shipment. The condition of each unit is stated in the quote, and batch pricing applies to volume orders.