JEDEC DDR5 JC-42

introducing-ddr5

The JEDEC DDR5 JC-42 is tasked with developing DDR5 as part of the solid state memories standard. DDR5 is still a fair ways off before it surfaces in gaming rigs.

Initially the JEDEC is expected to double the speed from DDR4 as well as double the capacity of memory sticks.

Realistically the JEDEC should scale speeds to far higher levels to eliminate the need for proprietary solutions. DDR4 speeds are already well above DDR4-3200 which is the top speed in the current standard. JEDEC DDR5-6400 is likely to be exceeded before long.

At present 16 gigabit DDR4 chip are in mass production which affords 32GB memory sticks. DDR5 will afford 64GB and 128GB DIMMs. DDR5 for extreme servers will top out at 2TB.

  • The number of chip ID bits remains at 3, allowing up to 8 stacked chips.
  • A third bank group bit (BG2) was added, allowing up to 8 bank groups.
  • The maximum number of banks per bank group remains at 4.
  • The number of row address bits remains at 17, for a maximum of 128K rows.
  • One more column address bit (C10) is added, allowing up to 8192 columns (1 KB pages) in ×4 chips.
  • The least-significant three column address bits (C0, C1, C2) are removed; all reads and write must begin at a column address which is a multiple of 8.
  • One bit is reserved for addressing expansion as either a fourth chip ID bit (CID3) or an additional row address bit (R17).

The JEDEC should consider that 32 gigabit memory chips will move into mass production for consumer systems now that the average selling price of 16 gigabit chips has softened. The price for 8 gigabit chips is now close to $1 and falling fast. It’s now only a matter of time before 64 gigabit memory chips becomes mass produced but corporate demand for servers is still very high. Samsung has 128 gigabit DDR4 chips but these are being sold to the server market at the high end of the market. Sooner or later 256 gigabit chips and even 512 gigabit chips are inevitable but prices are simply unaffordable for the gaming market.

Back in 1970, a mainframe came with up to 256KB of memory. The move to 1MB heralded the development of multi user systems. In 2015, the iPhone offered 1GB of RAM. Mainframe systems used SDRAM for years until the patents finally expired and the PC market was able to adopt the approach. With more refinements SDRAM has dominated the PC market.

The market will be different in 2025 and different again in 2030. The crystal ball at Hardcore Games suggests that consumer machines may reach 256GB before long and eventually 1TB is possible.

jedec-ddr4-v-ddr5-pinout

Adding temperature sensors to the DDR5 DIMM makes sense in servers more than PC gaming rigs. Still its nice to keep an eye on RAM temperature and deal with it if it gets too warm. ECC is now going to be in everyone’s rig so stability should be slightly better. DDR5 also supports 2 rows of RAM chips but the density of RAM today is adequate for gaming. Even a database server is generally fine with 16GB of RAM. Microsoft Exchange Server used to be considered demanding but it also runs well with 16GB. The need for a Hyper-V box with 256GB or more is hard pressed with existing CPU limitations. The largest servers with 8 processors have 4TB of memory for extreme workloads.