Review the past and present life of DDR memory
2022-04-13
According to Von Norman's structure, there must be memory in the computer. So until today, memory and hard disks still play an important role in computers. Unlike large hard disks, memory has an amazing performance in access speed, but it cannot store stored information after a power failure. Therefore, in the long-term development of computer hardware, memory has been playing the role of a transit station. Like other hardware, memory follows Morgan's law, from the earliest SIMM to the emergence of DDR, and then iterates on the basis of DDR. Memory standards and specifications have changed dramatically.
Origin:
There was no memory strip on the original computer. The memory was installed directly on the DRAM socket of the motherboard as a DIP chip, and 8 to 9 such chips were needed. The capacity is only 64KB to 256KB, which is very difficult to expand. But that was enough for processors and programs at that time, until 80286 chips emerged, allowing hardware and software to crave more memory, and memory bars emerged.
In the 80286 era, we saw the early form of memory: SIMM (Single In-line Memory Modules). The initial SIMM memory was designed with 30Pin, with a single memory data bus of only 8 bits. Two SIMM memory bars are required for 16-bit data bus processors and four for 32-bit data bus processors. As a result, the cost of purchasing SIMM memory is not low at all, and failure rates are increased, the 30Pin SIMM memory is not welcomed by everyone.
72Pin SIMM memory was subsequently created, with a single memory bit width increasing to 32 bits, one that satisfies 32-bit data bus processors, and a 64-bit data bus processor that requires two. Memory capacity has also increased, from 256 KB in the 30 Pin era to 512 KB, 1 MB or even 2 MB. It soon replaced 30 Pin SIMM memory.
In the 72Pin memory era, there was another derivative, FP DRAM, also known as fast-page memory, but limited to how its timed refresh works, making data access to this memory less fast. However, this kind of memory has unexpectedly become the key to memory development, because later memory specifications are very similar in principle to FP DRAM.
Then, EDO RAM came to the public, which is also a type of 72Pin SIMM. It has larger capacity and more advanced addressing methods, simplifies data access smoothly, and reads much faster than FPM DRAM.
However, with the upgrade of the CPU, EDO RAM can no longer meet the needs of the system, memory technology has also undergone a major revolution, sockets from the original SIMM to DIMM (Dual In-line Memory Module), and memory ushered in the era of classic SDR SDRAM (Single Data Rate SDRAM, synchronous dynamic memory).
SDRAM brings new life to memory, and its 64-bit bandwidth is consistent with the processor's bus width at that time. This means that an SDRAM can keep your computer running properly, which greatly reduces the cost of memory purchase. Because the transmission signal of the memory is synchronized with the external frequency of the processor, the DIMM standard SDRAM is much faster than the SIMM memory in transmission speed.
Later, with the great success of Socket 478 Pentium, Intel began to "inflate" a little, and jointly with Rambus, it customized the Rambus DRAM memory specification to create the fastest memory product on the market. Its internal RISC architecture, high frequencies and high bandwidth were once considered the new favourites of the memory market, and Intel was confident in its Rambus DRAM, which, along with Pentium 4 processors, would build its own dynasty. However, Rambus was not eventually recognized by the market because of its high memory price and "huge" heat. Adding Rambus DRAM requires two installations to be able to use it, which greatly increases the threshold for this type of memory. Ultimately, Rambus DRAM did not withstand the test of the market and was stepped on by the cheaper DR SDRAM.
The failure of Rambus DRAM has given the market another focus on SDR SDRAM, but that year SDR SDRAM has become very old-fashioned. So SDRAM needs a new standard to move forward. Fortunately, this time memory hasn't taken a detour, so we see the new king of the memory market: DDR SDRAM.
DDR；
DDR (Double Data Rate) SDRAM, named in Chinese as Double Data Rate Synchronized Dynamic Random Access Memory, is an upgraded version of SDR SDRAM. DDR SDRAM transmits signals once along the rise and fall of the clock cycle, making it transmit data twice as fast as SDR SDRAM, without increasing power consumption. As for addressing and controlling signals, it transmits only along the rise. This was a compromise between memory controller compatibility and performance at the time.
DDR SDRAM uses 184Pin's DIMMM slot, and the gaps change from two when SDR SDRAM is in use to one, with a common operating voltage of 2.5V. The first generation of DDR memory frequency is 200MHz, followed by the slow birth of DDR-266, DDR-333 and the mainstream DDR-400 of that era, for those 500MHz, 600MHz, 700MHz are considered overfrequency bands. When DDR memory first came out there was only a single channel, then there was a chipset supporting two channels, which doubled the bandwidth of the memory directly and increased the capacity from 128MB to 1GB.
DDR2；
DDR2 (Double Data Rate 2) SDRAM is a new generation memory technology standard developed by JEDEC (Joint Commission on Electronic Equipment Engineering). The biggest difference between DDR memory technology standard and previous generation DDR memory technology standard is that DDR2 memory has more than twice the pre-read ability of previous generation DDR memory (i.e., 4-bit data read prefetch), although it uses the basic method of simultaneous data transmission along the rise/fall of clock. In other words, DDR2 memory can read/write data at 4 times the speed of the external bus and run at 4 times the speed of the internal control bus.
The biggest breakthrough point of DDR2 memory technology is not that users think it can transmit twice as much as DDR, but that DDR2 can get faster frequency boost with lower calorie and power consumption, breaking the 400MHZ limit of standard DDR. In addition, the DDR2 memory uses 1.8V voltage, which is much lower than 2.5V of the DDR standard. The frequency of DDR2 ranged from 400MHz to 1200MHz. At that time, the main stream was DDR2-800. In fact, the higher frequencies were all over-frequency bars. The capacity of DDR2 started from 256MB to the maximum of 4GB. However, the DDR2 of 4GB was very small, and at the end of the DDR2 era, the capacity of a single 2GB was mostly.
DDR3：
DDR3 provides higher performance and lower voltage than DDR2 SDRAM and is a successor to DDR2 SDRAM. Compared with previous generations, DDR3 has new specifications in many ways, with core voltage down to 1.5V and prefetching changing from 4-bit to 8-bit. This is also the key to improving bandwidth for DDR3, which provides twice as much bandwidth as DDR2 at the same core frequency. In addition, DDR3 adds CWD, Reset, ZQ, STR, RASR and other technologies.
DDR3 memory is the same 240Pin DIMM interface as DDR2 memory, but the gaps are different and cannot be mixed. Common capacities are 512MB to 8GB, and of course there is a single 16GB of DDR3 memory, but it is scarce. Frequency starts at 800MHz. Generally, the highest frequency that can be bought is 2400MHz. In fact, some manufacturers have introduced 3100MHz DR3 memory, but it is difficult to get it.
DDR4:
There are three main differences between DDR4 and DDR3: the 16bit prefetching mechanism (DDR3 is 8bit), and the theoretical speed is twice that of DDR3 at the same kernel frequency. More reliable transmission specifications, data reliability further improved; The working voltage drop is 1.2V, which saves energy.
The DDR4 memory pins increased from 240 to 288, and the anti-dementia gap was also different from the DDR3 position. Another change was that the DDR4 golden finger was slightly curved on both sides of the middle high, while the previous memory golden finger was straight. DDR4 not only maintained sufficient signal contact area with the DIMM slot, but also removed memory more easily than DDR3. Compared with DDR3, DDR4 can theoretically reach 512GiB per DIMM module, whereas DDR3 has a theoretical maximum of 128GiB per DIMM module. The number of banking units within a rank unit increased to 16, with each DIMM module having a maximum of 8 rank units.
DDR5:
As early as 2017, JEDEC, the organization responsible for the technical standards of computer memory, announced that it will complete the final standard of DDR5 memory in 2018. Magnesium Light, Samsung and other manufacturers will also start to develop 16GB DDR5 products in 2018, even in the last year several manufacturers have begun to gradually mass produce DDR5 memory. However, it was not until July 2020 that JEDEC officially released the DDR5 memory standard, with a jump of 4800MHz, much higher than previously thought.
According to JEDEC, the new DDR5 standard will provide twice the performance of previous generations and greatly improve power efficiency. Under the new DDR5 memory standard, the maximum memory transfer speed can reach 6.4Gbps, compared with 3.2Gbps under the DDR4 memory standard. In addition, DDR5 also improves the operating voltage of DIMM by reducing the voltage from 1.2V to 1.1V of DDR4, which further improves the energy efficiency performance of memory. In terms of memory density, the DDR5 memory standard will allow a single memory chip to have a density of 64 Gbit, which is four times higher than the 16Gbit density of the DDR4 memory standard. With such a high memory density, combined with multi-chip packaging technology, a stack of up to 40 cells can be achieved so that the effective memory capacity of the stacked LDIMM can reach 2TB.
Last:
From DDR to DDR5, there are two main differences in performance parameters: power supply voltage and data transfer rate. That is, the power supply voltage value is getting lower and lower while the data transfer rate is increasing geometrically. But now that memory standards have stabilized, it is difficult to find too many highlights in memory. Ultimately, of course, old things will be replaced by new things. When the day comes when DR5, which is not yet universal, can't better meet the needs of users or match the development of other hardware, new specifications will emerge.
Reprinted from://www.0101ssd.com/
Origin:
In the 80286 era, we saw the early form of memory: SIMM (Single In-line Memory Modules). The initial SIMM memory was designed with 30Pin, with a single memory data bus of only 8 bits. Two SIMM memory bars are required for 16-bit data bus processors and four for 32-bit data bus processors. As a result, the cost of purchasing SIMM memory is not low at all, and failure rates are increased, the 30Pin SIMM memory is not welcomed by everyone.
72Pin SIMM memory was subsequently created, with a single memory bit width increasing to 32 bits, one that satisfies 32-bit data bus processors, and a 64-bit data bus processor that requires two. Memory capacity has also increased, from 256 KB in the 30 Pin era to 512 KB, 1 MB or even 2 MB. It soon replaced 30 Pin SIMM memory.
In the 72Pin memory era, there was another derivative, FP DRAM, also known as fast-page memory, but limited to how its timed refresh works, making data access to this memory less fast. However, this kind of memory has unexpectedly become the key to memory development, because later memory specifications are very similar in principle to FP DRAM.
Then, EDO RAM came to the public, which is also a type of 72Pin SIMM. It has larger capacity and more advanced addressing methods, simplifies data access smoothly, and reads much faster than FPM DRAM.
However, with the upgrade of the CPU, EDO RAM can no longer meet the needs of the system, memory technology has also undergone a major revolution, sockets from the original SIMM to DIMM (Dual In-line Memory Module), and memory ushered in the era of classic SDR SDRAM (Single Data Rate SDRAM, synchronous dynamic memory).
SDRAM brings new life to memory, and its 64-bit bandwidth is consistent with the processor's bus width at that time. This means that an SDRAM can keep your computer running properly, which greatly reduces the cost of memory purchase. Because the transmission signal of the memory is synchronized with the external frequency of the processor, the DIMM standard SDRAM is much faster than the SIMM memory in transmission speed.
Later, with the great success of Socket 478 Pentium, Intel began to "inflate" a little, and jointly with Rambus, it customized the Rambus DRAM memory specification to create the fastest memory product on the market. Its internal RISC architecture, high frequencies and high bandwidth were once considered the new favourites of the memory market, and Intel was confident in its Rambus DRAM, which, along with Pentium 4 processors, would build its own dynasty. However, Rambus was not eventually recognized by the market because of its high memory price and "huge" heat. Adding Rambus DRAM requires two installations to be able to use it, which greatly increases the threshold for this type of memory. Ultimately, Rambus DRAM did not withstand the test of the market and was stepped on by the cheaper DR SDRAM.
The failure of Rambus DRAM has given the market another focus on SDR SDRAM, but that year SDR SDRAM has become very old-fashioned. So SDRAM needs a new standard to move forward. Fortunately, this time memory hasn't taken a detour, so we see the new king of the memory market: DDR SDRAM.
DDR；
DDR (Double Data Rate) SDRAM, named in Chinese as Double Data Rate Synchronized Dynamic Random Access Memory, is an upgraded version of SDR SDRAM. DDR SDRAM transmits signals once along the rise and fall of the clock cycle, making it transmit data twice as fast as SDR SDRAM, without increasing power consumption. As for addressing and controlling signals, it transmits only along the rise. This was a compromise between memory controller compatibility and performance at the time.
DDR SDRAM uses 184Pin's DIMMM slot, and the gaps change from two when SDR SDRAM is in use to one, with a common operating voltage of 2.5V. The first generation of DDR memory frequency is 200MHz, followed by the slow birth of DDR-266, DDR-333 and the mainstream DDR-400 of that era, for those 500MHz, 600MHz, 700MHz are considered overfrequency bands. When DDR memory first came out there was only a single channel, then there was a chipset supporting two channels, which doubled the bandwidth of the memory directly and increased the capacity from 128MB to 1GB.
DDR2；
DDR2 (Double Data Rate 2) SDRAM is a new generation memory technology standard developed by JEDEC (Joint Commission on Electronic Equipment Engineering). The biggest difference between DDR memory technology standard and previous generation DDR memory technology standard is that DDR2 memory has more than twice the pre-read ability of previous generation DDR memory (i.e., 4-bit data read prefetch), although it uses the basic method of simultaneous data transmission along the rise/fall of clock. In other words, DDR2 memory can read/write data at 4 times the speed of the external bus and run at 4 times the speed of the internal control bus.
The biggest breakthrough point of DDR2 memory technology is not that users think it can transmit twice as much as DDR, but that DDR2 can get faster frequency boost with lower calorie and power consumption, breaking the 400MHZ limit of standard DDR. In addition, the DDR2 memory uses 1.8V voltage, which is much lower than 2.5V of the DDR standard. The frequency of DDR2 ranged from 400MHz to 1200MHz. At that time, the main stream was DDR2-800. In fact, the higher frequencies were all over-frequency bars. The capacity of DDR2 started from 256MB to the maximum of 4GB. However, the DDR2 of 4GB was very small, and at the end of the DDR2 era, the capacity of a single 2GB was mostly.
DDR3：
DDR3 provides higher performance and lower voltage than DDR2 SDRAM and is a successor to DDR2 SDRAM. Compared with previous generations, DDR3 has new specifications in many ways, with core voltage down to 1.5V and prefetching changing from 4-bit to 8-bit. This is also the key to improving bandwidth for DDR3, which provides twice as much bandwidth as DDR2 at the same core frequency. In addition, DDR3 adds CWD, Reset, ZQ, STR, RASR and other technologies.
DDR3 memory is the same 240Pin DIMM interface as DDR2 memory, but the gaps are different and cannot be mixed. Common capacities are 512MB to 8GB, and of course there is a single 16GB of DDR3 memory, but it is scarce. Frequency starts at 800MHz. Generally, the highest frequency that can be bought is 2400MHz. In fact, some manufacturers have introduced 3100MHz DR3 memory, but it is difficult to get it.
DDR4:
There are three main differences between DDR4 and DDR3: the 16bit prefetching mechanism (DDR3 is 8bit), and the theoretical speed is twice that of DDR3 at the same kernel frequency. More reliable transmission specifications, data reliability further improved; The working voltage drop is 1.2V, which saves energy.
The DDR4 memory pins increased from 240 to 288, and the anti-dementia gap was also different from the DDR3 position. Another change was that the DDR4 golden finger was slightly curved on both sides of the middle high, while the previous memory golden finger was straight. DDR4 not only maintained sufficient signal contact area with the DIMM slot, but also removed memory more easily than DDR3. Compared with DDR3, DDR4 can theoretically reach 512GiB per DIMM module, whereas DDR3 has a theoretical maximum of 128GiB per DIMM module. The number of banking units within a rank unit increased to 16, with each DIMM module having a maximum of 8 rank units.
DDR5:
As early as 2017, JEDEC, the organization responsible for the technical standards of computer memory, announced that it will complete the final standard of DDR5 memory in 2018. Magnesium Light, Samsung and other manufacturers will also start to develop 16GB DDR5 products in 2018, even in the last year several manufacturers have begun to gradually mass produce DDR5 memory. However, it was not until July 2020 that JEDEC officially released the DDR5 memory standard, with a jump of 4800MHz, much higher than previously thought.
According to JEDEC, the new DDR5 standard will provide twice the performance of previous generations and greatly improve power efficiency. Under the new DDR5 memory standard, the maximum memory transfer speed can reach 6.4Gbps, compared with 3.2Gbps under the DDR4 memory standard. In addition, DDR5 also improves the operating voltage of DIMM by reducing the voltage from 1.2V to 1.1V of DDR4, which further improves the energy efficiency performance of memory. In terms of memory density, the DDR5 memory standard will allow a single memory chip to have a density of 64 Gbit, which is four times higher than the 16Gbit density of the DDR4 memory standard. With such a high memory density, combined with multi-chip packaging technology, a stack of up to 40 cells can be achieved so that the effective memory capacity of the stacked LDIMM can reach 2TB.
Last:
From DDR to DDR5, there are two main differences in performance parameters: power supply voltage and data transfer rate. That is, the power supply voltage value is getting lower and lower while the data transfer rate is increasing geometrically. But now that memory standards have stabilized, it is difficult to find too many highlights in memory. Ultimately, of course, old things will be replaced by new things. When the day comes when DR5, which is not yet universal, can't better meet the needs of users or match the development of other hardware, new specifications will emerge.
Reprinted from://www.0101ssd.com/