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RAM: DDR5 specifications are final – Golem.de

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The standard is official: the Jedec storage committee has finalized the specification for DDR5-SDRAM (JESD79-5). The RAM is intended for future PCs and servers: For this, DDR5 has significant improvements in speed, capacity and efficiency. Our detailed background article provides a deeper insight That can DDR5 RAM, hereinafter an abbreviated version of it.

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DDR5 follows DDR4, the production of corresponding chips and modules has already started. Manufacturers such as Samsung, Micron and SK Hynix will ramp up production in the coming months, because by 2021 a quarter of the RAM sold will be made available by DDR5 and the share will increase to over 40 percent by 2022. The background is the almost parallel introduction of x86 processors in the server segment, which support DDR5 and which are used in most systems worldwide. There are also chips with power and ARM-based designs.

While the Jedec has specified a maximum of DDR4-3200, up to DDR5-8400 is currently planned, but the market launch should take place with DDR5-4800. It should be taken into account that DDR5-3200 already has more effective bandwidth than DDR4-3200. The new RAM supports two independent 32-bit channels, data prefetching with 16n instead of 8n simultaneous accesses, twice as many memory bank groups (8Gx4B instead of 4Gx4B), also Same Bank Refresh for lower latency and the burst length doubles 8 on 16.

DDR4 DDR5
Data transfer rate DDR4-3200 (Jedec) DDR5-6400 to DDR5-8400
Bandwidth (theoretical) 25.6 GB / s per channel 51.2 GB / s to 67.2 GB / s per channel
Data lines 64 + 8 bit with ECC 2x 32 + 8 bits with ECC
Error correct Off-Die-ECC On-Die-ECC (optional)
SDRAM die capacity up to 16 GBit (DUV) up to 64 GBit (EUV)
DIMM capacity (desktop) up to 32 GB up to 128 GB
DIMM capacity (server) up to 256 GB up to 1 TB
Prefetching 8n 16n
Memory banks 4 groups with 4 banks 8 groups with 4 banks
refreshing All Bank Refresh (REFab) Same Bank Refresh (REFsb)
Burst length 8th 16
Voltage (VDD / VPP) 1.2 volts / 2.5 volts 1.1 volts / 1.8 volts

Comparison of DDR5 and DDR4

Lower operating voltages of 1.1 volts instead of 1.2 volts (VDD / VDDQ) or 1.8 volts instead of 2.5 volts (VPP) are also important. In the future, Samsung, Micron and SK Hynix want to switch their DRAM processes to a 1A nm node. Instead of tried-and-tested immersion lithography (DUV), the logic chips are therefore manufactured with extremely ultraviolet exposure (EUV), which makes them more compact and economical. Current DRAM chips for DDR4 memory use 16 GBit dies, but DDR5 dies with 64 GBit are planned. The DIMM capacity therefore increases from 32 GB to 128 GB (desktop) and from 256 GB to 1 TB (server). The first CPUs with DDR5 memory are AMDs Genoa, Intel’s Sapphire Rapids and IBM’s Power10.

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