DDR3 vs. DDR4. Theoretical differences
The differences between the generations of RAM is always quite significant. Last year’s entry into the DDR4 standard made the server segment and the high-performance desktop somewhat out of line. The recent announcement of the Intel Atom server processors pulled the SO-DIMM DDR4 behind. Everything is ready for a mass attack on the market, and not just a debut. We study a little theory, refresh knowledge? Under the cut are the key differences between DDR3 and DDR4.
Of course, physically DDR3 and DDR4 memory bars are incompatible. Instead of 240 pins, the “third” - “fourth” has 288 contacts. The increase in the number of contacts is made for the possibility of addressing as much memory as possible. In the very maximum version, the DDR4 standard memory module can have a volume of 512 gigabytes. The minimum module size is 2 gigabytes.
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Connector key is shifted closer to the center. Protection from inattentive users works, protection from inattentive, but very strong users does not exist.
The height of the reference bar - 31.25 mm is slightly higher than that of its predecessor (30 mm). The length of the bar is the same - 133.35 mm (remind me how much is it in inches?), 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 proposed. The advantages are obvious: less heat, less power consumption, in the future: longer battery life.
If the DDR3 standards start at 1066 MHz, then DDR4 starts at 2133 MHz. Formally, the frequency increase is doubled, but in reality the performance does not grow twice. DDR4 modules with a frequency of 3000 MHz have already been officially released and there are even higher rates, but all of them are aimed at enthusiasts and overclockers.
The most important thing that happened during the transition was the 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 have a positive effect on performance.
The new bus with the original name Point-to-Point will connect 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 four-channel memory, four slots will be available. You tell me, what about boards with 8 slots for memory? For them, digital switches are used - similar in meaning to those that branch out the PCI Express lines. Thus, the RAM switches to using parallel access.
Another important point is the change in the organization of memory chips. With an equal volume, the DDR4 chip will have twice the memory banks and memory strings are four times shorter. This suggests that the new standard will switch between banks much faster than DDR3.
In short, these are all key differences between the two generations of DDR3 and DDR4 RAM, how does this affect practice? Are there any tangible differences in performance - we will find out in the following posts. Stay with us.
Physical differences.
Of course, physically DDR3 and DDR4 memory bars are incompatible. Instead of 240 pins, the “third” - “fourth” has 288 contacts. The increase in the number of contacts is made for the possibility of addressing as much memory as possible. In the very maximum version, the DDR4 standard memory module can have a volume of 512 gigabytes. The minimum module size is 2 gigabytes.
')
Connector key is shifted closer to the center. Protection from inattentive users works, protection from inattentive, but very strong users does not exist.
The height of the reference bar - 31.25 mm is slightly higher than that of its predecessor (30 mm). The length of the bar is the same - 133.35 mm (remind me how much is it in inches?), 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 proposed. The advantages are obvious: less heat, less power consumption, in the future: longer battery life.
Frequency differences.
If the DDR3 standards start at 1066 MHz, then DDR4 starts at 2133 MHz. Formally, the frequency increase is doubled, but in reality the performance does not grow twice. DDR4 modules with a frequency of 3000 MHz have already been officially released and there are even higher rates, but all of them are aimed at enthusiasts and overclockers.
Architectural differences.
The most important thing that happened during the transition was the 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 have a positive effect on performance.
The new bus with the original name Point-to-Point will connect 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 four-channel memory, four slots will be available. You tell me, what about boards with 8 slots for memory? For them, digital switches are used - similar in meaning to those that branch out the PCI Express lines. Thus, the RAM switches to using parallel access.
Another important point is the change in the organization of memory chips. With an equal volume, the DDR4 chip will have twice the memory banks and memory strings are four times shorter. This suggests that the new standard will switch between banks much faster than DDR3.
In short, these are all key differences between the two generations of DDR3 and DDR4 RAM, how does this affect practice? Are there any tangible differences in performance - we will find out in the following posts. Stay with us.
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Source: https://habr.com/ru/post/365275/
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