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The Evolution From DDR1 to DDR6

Key Takeaways

  • DDR6 is the next-generation memory standard. 

  • When SDRAM works on the rising as well as the falling edge of a clock signal, it forms a faster version of SDRAM called DDR SDRAM. 

  • DDR6 technology doubles the data transfer rate and achieves a speed in a range greater than ten thousand Mbps.

 DDR6

DDR6 is the next-generation memory standard

It is difficult to work on a computing device when there is not enough random access memory (RAM). RAM is an essential element in PCs, smartphones, cloud computing, and networking. As memory generations evolve, it challenges chip and board-level design. To accommodate this, there are different generations of RAM, each with improvements in speed and bandwidth, starting from DDR1 to DDR6. DDR6 technology doubles data transfer rates and achieves a speed in a range greater than ten thousand Mbps. In this article, we will discuss the evolution of RAM from DDR1 to DDR6.   

Random Access Memory 

In computer memory, there is internal and external memory. The internal memory is a storage space for data that needs to be accessed quickly by the computer during its functioning. The external memory can be an embedded or removable storage device that stores data persistently. Hard disks, USB flash memories, and solid-state devices are examples of external memory.

Internal memory is of two types: read-only memory (ROM) and random access memory (RAM). 

  1. ROM is non-volatile memory that retains data without power. The boot-up program of computers is stored in ROM. 
  2. RAM stores data temporarily when the central processing unit (CPU) is executing other tasks. RAM is volatile memory, as the data can't be retained when the computer is not powered. 

A computer with high RAM capacity works faster than one with less RAM capacity. With more RAM, the CPU doesn’t have to read as much data from secondary memories, which enhances the speed of the device. 

Types of RAM  

There are two types of RAM:

  1. Dynamic RAM (DRAM) - DRAM is a type of semiconductor memory that forms the primary or main memory of computing devices. A DRAM memory cell is made up of transistors and capacitors arranged within an integrated circuit. Data bits can be stored in the capacitor in the form of charge. The capacitor slowly discharges due to the leakage of the transistor and the data stored in DRAM drains out. The DRAM should be refreshed periodically to retain data, which charges the capacitor. 
  2. Static RAM (SRAM) -  SRAM consists of four or six transistors that keep the data as long as it is powered. SRAM is faster than DRAM and is more expensive. SRAM is used to build the Cache memory. 

We will focus on types of DRAM in the upcoming section. 

Types of DRAM 

The types of DRAM are:

  1. Rambus DRAM (RDRAM) - RDRAM uses various mechanisms—such as very fast signal timing, synchronous memory interface, and caching inside the DRAM chips—to achieve a very high data transfer rate. 

  2. Cache DRAM - This type of DRAM contains an on-chip cache memory. Cache DRAM is a high-speed buffer for the main DRAM. 

  3. Asynchronous DRAM (ADRAM) - In this type of DRAM, memory cell timing is controlled asynchronously using a specialized memory controller. There is a delay in the response of the memory with respect to the CPU clock signal. 

  4. Synchronous DRAM (SDRAM) - When the access speed of the RAM chips is synchronized with the CPU’s clock, such DRAMs are called synchronous DRAMS. The memory speed syncs with the clock speed of the CPU and allows the CPU to execute more instructions at a time. SDRAMs operate at the CPU memory bus and there are no wait states associated with them. 

  5. Double Date Rate (DDR) SDRAM - The standard SDRAM operates on the rising edge of the clock signal. When the SDRAM works on the rising as well as the falling edge of the clock signal, it forms a faster version of SDRAM called DDR SDRAM. The data rate is doubled compared to standard SDRAM, as data transfer occurs on both the edges of the clock signal. 

Let’s look at the evolution of DDR SDRAM.

Evolving From DDR1 to DDR6

DDR SDRAMs underwent several iterations, and the generations of SDRAM evolved from DDR1 to DDR6.

  1. DDR SDRAM or DDR1: DDR1 doubles the bandwidth in the data rate without increasing the internal clock frequency. DDR1 comprises 184 pins and a single notch on the connector. It works at a low voltage of 2.5 V to 3.3 V.
  2. DDR2: DDR2 is the upgraded successor of DDR1 and operates the external data bus two times faster than DDR1. The internal clock speed can go up to 200MHz and the transfer rates can reach from 533-800 mega transfers per sec (MT/s). There is no backward compatibility with its predecessor. 
  3. DDR3: Compared to DDR2, the power consumption of DDR3 is reduced up to 40% by lowering the operating current and voltage. DDR3 offers improved reliability, memory capacity, and clock speed. The transfer rates are in the range of 800-1600 MT/s. This generation lacks backward compatibility.
  4. DDR4: DDR4 offers an even lower operating voltage and higher transfer rate (23133-3200 MT/s) than DDR3. 
  5. DDR5: DDR5 operates at double the speed of DDR4, with transfer rates hitting 3200-6400 MT/s.
  6. DDR6: DDR6 is two times faster than its immediate predecessor and four times faster than DDR4. It is the next-generation memory standard. DDR6 speed can be in the range of 12800 Mbps and go up to 17000 Mbps when overclocked. The number of memory channels per module of DDR6 is doubled, which provides greater capacity, reliability, speed, and performance. 

Each generation of DRAM is better than its predecessor. As the generations of DRAM evolve from DDR1 to DDR6, they bring challenges in chip-level and board-level design. Signal integrity and  power integrity problems are critical in DDR6. Cadence offers tools that are suitable for layout and routing designs for high-speed applications. If you’re looking to learn more about how Cadence has the solution for you, talk to our team of experts.