March 24, 2015 at 18:17DDR3 vs DDR4. Theoretical differences
The differences between generations of RAM are always quite significant. Last year’s release in the DDR4 standard people made the server segment and high-performance desktop somewhat out of the general row. The recent announcement of Intel Atom server processors pulled the SO-DIMM DDR4. Everything is ready for a massive attack on the market, not just a debut. We learn a little theory, refresh knowledge? Under the cut key are the key differences between DDR3 and DDR4.
Of course, physically the memory strips DDR3 and DDR4 are incompatible. Instead of 240 pins from the “third” - “fourth” has 288 contacts. The increase in the number of contacts has been done in order to address as much memory as possible. At its maximum, a DDR4 memory module can have a capacity of 512 gigabytes. The minimum module size is 2 gigabytes.
The connector key is biased closer to the center. Protection against inattentive users works, protection against inattentive, but very strong users - does not exist.
The height of the reference bar - 31.25 mm - is slightly higher than that of the predecessor (30 mm). The length of the bar is the same - 133.35 mm (remind me how many inches it is?), This parameter has not changed since the advent of the first generation of DDR RAM.
Instead of the standard supply voltage of 1.5V (1.35V for Haswell), a standard voltage of 1.2V (1.05V for energy-efficient systems) is offered. The advantages are obvious: less heat, less power consumption, in the future: longer battery life.
If DDR3 standards start at 1066 MHz, then DDR4 starts at 2133 MHz. Formally, the frequency is doubled, but in reality productivity does not double. Already officially released DDR4 modules with a frequency of 3000 MHz and there are even higher rates, but they are all aimed at enthusiasts and overclockers.
The most important thing that happened during the transition was a change in the architecture of access to the modules. Previously, the Multi-Drop bus had only two channels, and even when organizing work with four memory modules, they hung in pairs on one channel, which did not always positively affect performance.
A new bus with the original name Point-to-Point will associate each channel with one memory module. That is, if there is a dual-channel memory controller in the processor, two slots will be available, and if there is a four-channel memory, four. You tell me, but what about boards with 8 memory slots? For them, digital switches are used - similar in meaning to the fact that they branch out PCI Express lines. Thus, the RAM switches to using parallel access.
Another important point is the change in the organization of memory chips. With equal volume, the DDR4 chip will have twice as many memory banks and memory lines four times shorter. This suggests that the new standard will switch between banks much faster than DDR3.
In short, these are all the key differences between the two generations of DDR3 and DDR4 RAM, how is this reflected in practice? Are there any noticeable differences in performance? We will find out in the following posts. Stay with us.
Physical differences.
Of course, physically the memory strips DDR3 and DDR4 are incompatible. Instead of 240 pins from the “third” - “fourth” has 288 contacts. The increase in the number of contacts has been done in order to address as much memory as possible. At its maximum, a DDR4 memory module can have a capacity of 512 gigabytes. The minimum module size is 2 gigabytes.
The connector key is biased closer to the center. Protection against inattentive users works, protection against inattentive, but very strong users - does not exist.
The height of the reference bar - 31.25 mm - is slightly higher than that of the predecessor (30 mm). The length of the bar is the same - 133.35 mm (remind me how many inches it is?), This parameter has not changed since the advent of the first generation of DDR RAM.
Electrical differences.
Instead of the standard supply voltage of 1.5V (1.35V for Haswell), a standard voltage of 1.2V (1.05V for energy-efficient systems) is offered. The advantages are obvious: less heat, less power consumption, in the future: longer battery life.
Frequency differences.
If DDR3 standards start at 1066 MHz, then DDR4 starts at 2133 MHz. Formally, the frequency is doubled, but in reality productivity does not double. Already officially released DDR4 modules with a frequency of 3000 MHz and there are even higher rates, but they are all aimed at enthusiasts and overclockers.
Architectural differences.
The most important thing that happened during the transition was a change in the architecture of access to the modules. Previously, the Multi-Drop bus had only two channels, and even when organizing work with four memory modules, they hung in pairs on one channel, which did not always positively affect performance.
A new bus with the original name Point-to-Point will associate each channel with one memory module. That is, if there is a dual-channel memory controller in the processor, two slots will be available, and if there is a four-channel memory, four. You tell me, but what about boards with 8 memory slots? For them, digital switches are used - similar in meaning to the fact that they branch out PCI Express lines. Thus, the RAM switches to using parallel access.
Another important point is the change in the organization of memory chips. With equal volume, the DDR4 chip will have twice as many memory banks and memory lines four times shorter. This suggests that the new standard will switch between banks much faster than DDR3.
In short, these are all the key differences between the two generations of DDR3 and DDR4 RAM, how is this reflected in practice? Are there any noticeable differences in performance? We will find out in the following posts. Stay with us.
