DDR4 and DDR5 are not interchangeable at any level - different notch position, different voltage (1.2V vs 1.1V per Samsung's own spec pages), and DDR5 moves voltage regulation onto the module itself via an on-DIMM PMIC. Your platform's memory controller is built for one generation only; Samsung states plainly that the two "cannot be mixed because they use different slot designs, signaling methods, and electrical characteristics." The module physically will not fit the wrong slot.
Updated ยท vendor documents read 16 September 2026
Both generations use a notched connector - a small gap in the row of contacts that lines up with a matching key in the slot. The two generations put that notch in different positions specifically so the wrong module cannot be forced in. Samsung's own DDR5 documentation states it directly: "The notch on a DDR5 module is located differently from that of DDR4, so it cannot be inserted into a DDR4 slot." This is not a software restriction or a marketing distinction - it is a physical fact about the connector, stated by a manufacturer of the modules themselves.
We could not confirm the specific pin-count figure often repeated for each generation from a source we could render this session, so we are not stating one here - see the sourcing note at the bottom of this page for what we tried and why it is omitted rather than repeated from memory.
DDR4 operates at 1.2V; DDR5 drops to 1.1V. SK hynix's own DDR5 explainer states the figure directly: "with an operating voltage of 1.1V, lowered from DDR4's 1.2V, DDR5 aims to reduce power consumption per bandwidth by more than 20% of its predecessor." That is a real architectural change, not a rounding difference - and it is one reason the two generations cannot share a socket even if the notch problem did not exist on its own.
DDR5 also moves voltage regulation onto the module itself. Per Samsung's own documentation: "DDR5 modules also often include a PMIC (Power Management IC) on the PCB for power management, which makes the module look more complex compared to DDR4," and separately, "the on-DIMM PMIC enables more efficient power regulation and stable power delivery." DDR4 has no equivalent component - voltage regulation for a DDR4 module happens on the motherboard, not on the module.
None of this is a buyer's choice to make per-module. A server's memory controller - built into the CPU on every platform this site tracks - supports exactly one DDR generation, decided at the time the platform was designed. Samsung's own buying guidance states the consequence in one sentence: "Different DDR generations, such as DDR4 and DDR5, cannot be mixed because they use different slot designs, signaling methods, and electrical characteristics, making them incompatible with each other." The question a buyer actually answers is not "which generation should I buy" - it is "which generation does my platform already require," and the keying above makes getting that wrong a non-event rather than a risk: the module simply will not seat.
Same-generation speed mixing is a separate, narrower question, and Samsung's own FAQ addresses it too: modules of different speeds within one generation "can be mixed, but all modules will operate at the speed of the slowest one." That rule has nothing to do with the generation-mixing question above - it never applies across DDR4 and DDR5, only within one or the other.
Do not infer it from a CPU family name or a launch year - read what the platform actually documents, or read what is physically installed. Our how-to-check-installed-memory page covers the OS-native commands (Windows and Linux) and the BMC-level methods (iDRAC, iLO) that report this without opening the chassis. For a specific model, the OEM's own platform page is the final authority - see our OEM-verified platform pages, or the manufacturer's own documentation where we have not built one.
Cheapest in-stock modules of each generation right now, computed live rather than quoted from a snapshot.
| Generation | Brand | Module | Capacity | Type | $/GB | |
|---|---|---|---|---|---|---|
| DDR4 | SK Hynix | HMAA8GL7MMR4N | 64GB | RDIMM | $4.61 | Buy Now |
| DDR4 | A-Tech | M393A2G40DB0-CPB | 16GB | RDIMM | $5.44 | Buy Now |
| DDR4 | Samsung | M393A8K40B22-CWD | 64GB | RDIMM | $6.23 | Buy Now |
| DDR4 | Supermicro | B07DFLTWN3 | 64GB | LRDIMM | $6.23 | Buy Now |
| DDR4 | Samsung | M393A2G40EB1-CPB | 16GB | RDIMM | $7.12 | Buy Now |
| DDR4 | MICRON | MTA36ASF4G72PZ | 32GB | RDIMM | $7.19 | Buy Now |
| DDR5 | Samsung | M321R2GA3BB6-CQK | 16GB | RDIMM | $29.56 | Buy Now |
| DDR5 | Kingston | KSM56R46BD8PMI | 32GB | RDIMM | $31.25 | Buy Now |
| DDR5 | Kingston | KSM56R46BD4PMI | 64GB | RDIMM | $32.25 | Buy Now |
| DDR5 | A-Tech | B0DMC1VFNS | 96GB | RDIMM | $32.70 | Buy Now |
| DDR5 | Samsung | M321RYGA0BB0-CQK | 96GB | RDIMM | $32.70 | Buy Now |
| DDR5 | Samsung | M321R8GA0BB0-CQK | 64GB | RDIMM | $35.08 | Buy Now |
Nothing on this page tells you which generation your specific server accepts - that answer lives in the platform's own documentation, never inferred from a CPU generation or chipset name. See our OEM-verified platform pages for Dell, HPE, Lenovo and Supermicro models we have checked directly, or the manufacturer's own memory specifications page for anything we have not yet built.
The specific pin-count figure commonly repeated for DDR4 and DDR5 (both generations are often quoted as 288-pin) did not come back confirmed from any source we could render this session - Kingston, Crucial and JEDEC all returned bot-detection blocks or WAF rejections to every URL attempted, and no other vendor page we reached stated the raw pin-count number. Samsung's own documentation confirms the notch-position mechanism in detail without stating the pin count itself. Rather than repeat a widely-circulated figure we could not verify against a primary source today, we simply do not state one here.
No. Per Samsung's own DDR5 documentation: "DDR5 and DDR4 use different physical slot designs, electrical requirements, and signaling methods... the memory controller on a DDR4 motherboard does not support DDR5." The notch on the module connector sits in a different position between the two generations specifically to prevent this.
No - Samsung's own spec pages list DDR4 at 1.2V and DDR5 at 1.1V. SK hynix's own explainer states the change directly: "with an operating voltage of 1.1V, lowered from DDR4's 1.2V, DDR5 aims to reduce power consumption per bandwidth by more than 20% of its predecessor."
A Power Management IC mounted on the DIMM itself. Per Samsung's own documentation, DDR5 moves voltage regulation onto the module rather than the motherboard: "DDR5 modules also often include a PMIC (Power Management IC) on the PCB for power management, which makes the module look more complex compared to DDR4."
No - this is not a supported configuration on any platform, because it is not a module-compatibility question at all: a memory controller is built for one generation. Samsung states it plainly: "Different DDR generations, such as DDR4 and DDR5, cannot be mixed because they use different slot designs, signaling methods, and electrical characteristics, making them incompatible with each other."
Read what is actually installed rather than guessing from the CPU generation name - see our how-to-check-installed-memory page for the OS-native and BMC methods. Your platform's own documentation is the final word; see our /server-ram/for/ pages for OEM-verified specifics per model.
Sometimes, and only up to a point the vendor documents - per Samsung: "memory modules within the same DDR generation but with different speeds... can be mixed, but all modules will operate at the speed of the slowest one." That is a same-generation speed question, entirely separate from the generation-mixing question this page answers - it does not extend to mixing DDR4 with DDR5 under any circumstance.
Specification claims on this page were checked against the pages below on 16 September 2026. Where a widely-repeated figure did not survive that check, we report what the source says now and say so in the text rather than repeating the familiar number.