TECH

What We Know About DDR5 So Far

Double Data Rate 5 (DDR5) is the next-generation standard for random-access memory (RAM). The new specification promises to bring chips that have much higher performance than the existing DDR4 modules, as well as lower power consumption. But what does that mean for desktop PCs? Let's take a look at what we know so far.
Why We Need DDR5 RAM
With the launch of AMD's first-generation Ryzen processors, the new Core War began. AMD delivered quad-core / eight-thread processors at mid-range and eight-core / 16-threads CPUs at the high end for mainstream PC consumers, which was just about what Intel had been offering for years in those ranges.
With the third-generation Ryzen processors, AMD has increased the core count by another 50%, pushing six-core chips at mid-range and 12-colors at the high end. Intel has also been forced to respond with an increase in the number of colors for its own processors, although Intel has not been nearly as aggressive as AMD.
In less than three years we went from four colors being just about the highest number most gamers or regular PC users could expect in their computers to three times as many. What all of this means is that we're going to need to drastically increase our bandwidth per core, too, if our PCs are going to keep up with AMD and Intel's core war.

Credit: Micron
As we can see from Micron's chart above, bandwidth per core has remained relatively stable since the early 2000s. However, bandwidth per core has started to decline since last year.
DDR5 Performance
DDR5 designs promise to arrive on the market with double the density as well as double the performance of the first-generation DDR4 modules.
DDR5-3200 RAM will see an increase of 1.36x in bandwidth compared to DDR4-3200. However, DRAM chips are expected to ship with a bandwidth of 4800MT / s, or 1.87x that of DDR4-3200 RAM. The official upper limit for the DDR5 RAM standard is 6400MT / s, but some designs may be able to push that further through overclocking.

Memory Type	Release Year	Bandwidth	Pins per Ch	Voltage (V)	Prefetch
SDR	1993	1.6 GB/s	168	3.3	1n
DDR	2000	3.2 GB/s	184	2.5/2.6	2n
DDR2	2003	8.5 GB/s	240	1.8	4n
DDR3	2007	17 GB/s	240	1.35/1.5	8n
DDR4	2014	25.6 GB/s	380	1.2	8n
DDR5	2019	32GB/s	380	1.1	8/16n
HBM2	2016	307 GB/s	2860	1.25/1.35	16n
GDDR6	2016	72 GB/s	180	1.35	16n

SK Hynix has been working on DDR5 modules that can deliver 16Gb (2GB) capacity per chip. The company measured voltage from 1.2V to 1.1V, which combined with the usage of its 1Ynm process, reduced power consumption compared to the company's DDR4 modules. The module offers up to 6.4Gb / s of throughput for each pin.
Other benefits of DDR5 RAM include two independent 40-bit channels per module, improved command bus efficiency, improved refresh schemes and an increased bank group for additional performance.
Features Enabling High-Bandwidth DDR5 RAM
According to Micron, DDR5 will use a completely overhauled architecture compared to DDR4, with a focus on increasing bandwidth. A number of key features enable this increase in bandwidth. The most important is that DDR5 can increase the data rates from 3,200 MTps to 6,400 MTps. This data rate should increase more than just keep up with potential future processors with even more colors.
The new DDR5 RAM standard also includes other new protocol features that are not related to the data rate transfers, but can still increase overall bandwidth. For instance, DDR5 DIMMs will support two 40-bit (32-bit + ECC) independent channels.
The new default burst length of 16 (BL16) in DDR5 RAM allows a single burst to access 64B of data, which is the typical CPU cache size, using only one of the two independent channels or the DIMM. This feature should provide significant improvement in concurrency and effectively move us from the 8-channel memory systems to a 16-channel system.

Credit: Micron DDR5 also doubles the number of bank groups (BGs) compared to DDR4, while keeping the number of banks per BG the same. This means that the total number of banks will be double that of DDR4. This helps controllers avoid performance degradation associated with sequential memory accesses within the same bank. All of these features and more point to how significant a DDR5 upgrade will be compared to DDR4.
First DDR5 Products to Ship In 2019
In March 2017, JEDEC, the group developing the DDR standard as well as other memory and storage standards, announced that it would release the DDR5 specification in 2018. In November 2018, SK Hynix announced the world's first DDR5-compliant RAM module, which the company initially said it would arrive in 2020.
However, since SK Hynix has said that it will release to DDR5 module by the end of 2019. Samsung and Micron have also previously said they would release DDR5 memory modules, but those may not be fully standard-compliant.

Credit: Micron SK Hynix predicted that DDR5 module sales would represent 25% of the RAM market in 2020 and 44% in 2021. The adoption of DDR5 RAM may be even faster in the mobile and data center markets. Smartphone makers (including Samsung) will want to outclass the competition with faster DDR5 LPDRAM, while data center customers will be seeking to satisfy their ever-increasing bandwidth needs. Meanwhile, we're still waiting for word on the arrival date for DDR5 for desktop PC, but this will likely hinge on AMD and Intel offering support on mainstream motherboards. Unfortunately, there have been no signs of DDR5 enablement from either company yet. Lucian Armasu