DDR5 ECC RAM

Bandwidth rises considerably. A DDR5-4800 channel delivers 38.4 GB/s in theory, a DDR4-3200 channel 25.6 GB/s. A fully populated EPYC 9004 therefore reaches about 460 GB/s per socket, a 4th Gen Xeon about 307 GB/s. Databases, HPC workloads and hosts with very high core counts benefit most.

Why DDR4 and DDR5 aren't interchangeable

Both module types have 288 pins, but the notch is in a different place, so a DDR5 module won't go into a DDR4 slot or vice versa. Behind that lie real electrical differences:

• Memory controller: it sits in the CPU and speaks exactly one memory generation. There are no adapters and no mixed operation.
• Power delivery: on DDR5 a chip on the module itself (the PMIC) regulates the voltage; the motherboard only supplies the input. Operating voltage drops from 1.2 to 1.1 V.
• Layout: every DDR5 module is split into two independent 32-bit sub-channels. A DDR5 RDIMM with ECC is therefore usually 80 bits wide rather than 72.

In practice, moving platforms – say from a Dell R740 to an R760 – always means new memory. You can sell your old DDR4 modules through our buy-back service and receive an offer within 48 hours.

Populating DDR5 RDIMMs: capacity and speed

As with DDR4, every channel should be populated the same way: 8 or 16 modules per CPU on Xeon, 12 or 24 on EPYC 9004. Typical configurations per socket:

• 4th/5th Gen Xeon: 8 × 32 GB = 256 GB or 8 × 64 GB = 512 GB, for example with the Samsung 64 GB DDR5-4800 RDIMM.
• EPYC 9004: 12 × 32 GB = 384 GB or 12 × 64 GB = 768 GB, for example with the Samsung 32 GB DDR5-4800 RDIMM.
• In-between sizes: DDR5 also comes in 24, 48 and 96 GB modules, provided BIOS and platform support them. Twelve 48 GB modules give 576 GB without resorting to two modules per channel.

Why DDR5 servers still need true ECC modules despite on-die ECC is explained in our guide ECC RAM: UDIMM, RDIMM and LRDIMM. All memory types are listed under server RAM; businesses can buy on invoice – see our page for business customers.