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DDR4 New changes brought by memory

日期: 2016-08-01
浏览次数: 436

As early as last September, Intel's flagship CPU Haswell-E and X99 chips announced the entry of memory into the DDR4 era. This year, Intel's next-generation 14nm Skylake architecture processor, together with the 100 series motherboards, made DDR4 memory really go from behind the scenes. Memory, from DDR, DDR2, to DDR3, each time the update will give a sharp impression of the history of hardware development. Of course, from DDR3 to DDR4, I believe it will be no exception.


     However, there is an argument that will soon spread in the DIY circle. 'The same frequency DDR3 vs. DDR4, DDR4 memory performance is in a disadvantage.' In theory, the new class of products of Massage Law should be better and better, and the performance is getting stronger. From a single technical perspective, JEDEC, the manufacturer of memory technology standards, has adopted many DDR3 memory technologies on DDR4 memory. So what is the difference in DDR3 and DDR4 memory performance? Today we will explore this issue.


DDR4 内存所带来新变化

DDR3 vs. DDR4 performance test: an era of contest

DDR4 New changes brought by memory:

(1) Data pre-existing mechanism 16bit (architecture and design)

DDR4 内存所带来新变化

Increasing the value of 'data pre-existing' is the main means of improving memory performance, from 2 bits of DDR to 4 bits of DDR2 and then to 8 bits of DDR3. But engineers have found that in the DDR4 era, data prefetching is getting more and more difficult, and DDR4 is not easy to directly access 16bit. Therefore, the Bank Group design of GDDR5 is adopted on DDR4 memory.


In fact, memory is a warehouse with its own transport capacity. To build a high-speed warehouse, there are two requirements: First, the warehouse itself will access the goods from the warehouse fast enough; Second, these goods can be quickly Transport to the outside. Similar to the logistics transfer station of the big e-commerce. Taking DDR3-1600 as an example, using the 8-bit pre-storage mechanism is equivalent to accessing 8 items at a time in the warehouse, but it is very efficient to carry the machine, and can perform 200 tasks per second (that is, the internal clock frequency of the memory is 200MHz). Therefore, the total number of goods accessed per second in the warehouse reaches 8x200=1600 pieces. However, this also requires the corresponding capabilities outside the warehouse. Although it can only access 2 items at a time, it can perform 800 tasks per second (that is, the memory I/O bus clock frequency is 800MHz), and its total cargo access is also 1600 pieces. In this way, the efficiency inside and outside the warehouse is consistent.


If you want to increase the number of accesses to the goods, in addition to the frequency of work, it is also feasible to increase the number of prefetches. However, due to the complicated design of the DDR4 memory, there are problems such as large heat generation, and it is difficult to increase the pre-stored number. JEDEC uses a tricky design to divide the warehouse into two small warehouses (up to four) and each warehouse is equipped with separate internal and transportation tools, the so-called Bank Group. Obviously, after adopting such a design, it is equivalent to raising the number of pre-accesses to two 8 bits, which is equivalent to 16 bits, and the number of pre-accesses of goods will double. However, the cost comes from the increased complexity of the internal design of the memory, resulting in an increase in memory latency, and the actual performance improvement will not reach the theoretical value.


We know that the delay is too large, which may cause the memory performance to rise and fall. For example, if DDR3-1600 takes 0.5 seconds to execute an access command, then the total time spent on a full 1600 item access task is 1+0.5 seconds, and the actual number of goods accessed per second is about 1600/1.5=1066. . If DDR4 1600 memory, the preparation time can reach 1+2.5 seconds, although it is 16bit, 3200 pieces per second, but the actual number of accesses per second is 3200/3.5=914 pieces, so it is concluded that at the same frequency, DDR4 may not be able to win DDR3, mainly related to the increased latency of DDR4.


(2) Frequency: up to 4266MHz


If you really think DDR4 is not as good as DDR3, then it is wrong. Because DDR4 is relatively 'noble', although the delay is higher than DDR3, it does not want to compete with DDR3 at the same frequency. DDR4 memory uses a new point-to-point bus technology that uses as much memory bandwidth as possible and supports higher memory frequencies. DDR4 starts at 2133MHz and the highest is 4266MHz. The larger 16-bit prefetch + higher frequency fully offsets the performance impact of high latency.


(3) Voltage: 1.2/1.35V voltage brings lower power consumption

DDR4 内存所带来新变化

The DDR4 memory uses the TCSE temperature compensation self-refresh technology (TCAR), which is mainly used to reduce the power consumed by the memory chip during self-refresh. In addition, the DBI (Data Bus Inversion) data bus is inverted to reduce the VDDQ current. These technologies can reduce the power consumption of DDR4 memory.


Of course, as a new generation of memory, the most straightforward way to reduce power consumption is to update the particle process and lower voltage. The DDR4 operating voltage is further reduced to 1.2V, and there may even be an ultra-low voltage energy-saving version of 1.1V/1.05V. Even the DDR4-3000 frequency operating voltage is only 1.35V. Compared to DDR3, the starting voltage is 1.5V, and the high frequency like DDR3-2133 and above must be 1.65V or higher.


 

(4) Appearance: Gold finger position change

DDR4 内存所带来新变化

The DDR4 gold finger has changed significantly, no longer a straight memory stick, but a curved one. Considering the inconvenient problem of straight memory gold finger insertion and removal, DDR4 changed the memory gold finger to a shape with a slightly protruding middle and a short edge. A smooth curve transitions at the high point of the center and the low point at both ends. This design can ensure that the gold finger and memory slot contacts of the DDR4 memory have enough contact surfaces, and the signal transmission ensures that the signal is stable, and the intermediate raised portion and the memory slot generate sufficient friction to stabilize the memory.

2DDR3 and DDR4 memory test and platform introduction

  

Having talked about these new changes and new technologies about DDR4, what is the difference in performance between DDR3 and DDR4? Next, we will verify them one by one.

Evaluation platform introduction and description:

Hardware platform

CPU

Intel Core i7-6700K
 Intel Core i7-4770K

Motherboard

Asus Z97-Deluxe
Asus MAIMUS VII HERO Z170

RAM

Ramsta Sirius DDR3-1600 4Gx2 10-10-10-27-1T

Kingston DDR4-2133 4Gx2 (15-15-15-35-2T)

 
 

hard disk

Main disk:Ramsta S600 480G

Graphics card

NVIDIA GeForce GTX 980Ti

power supply

Highpower 1000W

 

software platform

operating system

Windows 7 Ultimate X64 SP1

driver

NVIDIA ForceWare 350.12 WHQL

Evaluation plan

DDR3-1600DDR4-2133 Performance comparison

testing software

 Sisoftware Sandra(Test memory bandwidth and latency)
 ADIA 64 5.20.3400
(Test memory read, copy, and write performance)

  In order to ensure the accuracy of the test, we specially selected the i7-4770 K and i7-6700K of the Intel four generation and six generations of flagship positioning for the two platforms. Although the architecture is different from the main frequency, it is also quad-core and eight threads, and the performance is the same. small differences. It is equipped with Z97 motherboard supporting DDR3 memory and Z170 motherboard supporting DDR4 memory.

Tested DDR3 and DDR4 memory:

(1) DDR3-1600 and DDR4-2133

For DDR3, the 1600MHz frequency has become the starting frequency. The starting frequency of DDR4 is exactly 2133MHz. Let's see how the performance is at the default frequency. The tested memory is the Swiss Ramsta Sirius DDR3-1600 and Kingston DDR4-2133.

DDR4 内存所带来新变化

 

DDR3, DDR4 base frequency and same frequency PK

Test platform for DDR3-1600 memory:

DDR4 内存所带来新变化 

DDR3-1600MHz has already replaced 1333MHz as a general strip, and the default timing of the Swiss Ramsta Sirius DDR3-1600 is 10-10-10-27-1T, so the timing is much conservative compared to 1600MHz. There are some 1600MHz DDR3 memory timings available on the market as low as 8-8-8-24-1T. Due to the tight test time and limited samples, we chose the DDR3-1600 with a moderate timing, and the score will be worse than the low timing of 1600.

Test platform for DDR4-2133 memory:

DDR4 内存所带来新变化

Compared to the DDR3-1600 start frequency, the DDR4 memory start frequency reaches 2133MHz. The Ramsta Sirius DDR4-2133 default timing is 15-15-15-35-2T. Similarly, for DDR4-2133 memory, this timing is also conservative, which is complementary to DDR3-1600. Its operating voltage is only 1.2V.

Basic frequency PK: DDR3-1600 and DDR4-2133

AIDA64 Engineer 5.20.3400 software test:

DDR4 内存所带来新变化 
Test score comparison

DDR4 内存所带来新变化

Test score comparison 

Test Summary: First of all, this is an 'unfair' PK. 'Unfairness' is reflected in frequency inconsistency, a 1600MHz, a 2133MHz, test results are not suspense, DDR4-2133 results are better than DDR3-1600, and in terms of read, copy, write performance and memory bandwidth, The lead is larger. Although DDR3-1600 is more advanced in timing than DDR4-2133, the difference in frequency makes DDR4 perform better. However, careful users noticed that in the memory delay, DDR-1600 is 24.9ns, while DDR4-2133 is 23.1ns, the difference between the two is not obvious.


Through this comparison of data, it is mainly to see how DDR3 and DDR4 perform on the fundamental frequency. It is obviously consistent with the expectation that DDR4-2133 is better than DDR3-1600. 

 

DDR3 and DDR4 comparison performance test summary:

DDR4 内存所带来新变化

According to the above data comparison, the base frequency DDR4-2133 is better than DDR3-1600;

Then again, although there are some 100 series motherboards in the market that support both DDR3 and DDR4 memory, but with the popularity of Intel's next-generation platform, DDR4 has completely replaced DDR3, which seems to be only a matter of time. Choose DDR3 or DDR4? This is not up to us.

If you put the two on the same dimension, it doesn't make much sense. Because the platform is different, the specifications are not compatible, and the commonality between the two is not strong. The most important thing is that under the premise of solving the memory capacity at this stage, the performance of the memory can be described as more than enough. Among the three major components, the real bottleneck and short board are: hard disk. Moore's Law has always had little to do with memory performance...


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