Suppose you’ve bought or looked at computers over the last few years. In that case, you might have noticed that the system memory has gone through generations quickly. It wasn’t that long ago that DDR3 was the standard. Then DDR4 became the norm, and now DDR5 is being introduced. But what is DDR memory, the differences between the different versions, and is it worth upgrading?
What is DDR Memory?
DDR SDRAM is the type of memory that’s essentially been used in all computers since the first generation was standardized in the year 2000. DDR superseded its predecessor, SDRAM, which was retroactively renamed SDR. SDR stands for Single Data Rate, while DDR stands for Double Data Rate. This acronym gives away the core advantage of DDR over SDR. It can transmit data at twice the speed.
DDR uses a “double pumping” technique to transmit data on both the rising and falling edge of the clock signal. This alone doubles the bandwidth of DDR compared to SDR at the same clock speed. There were other changes, including reduced voltages, increased pin count, and a slightly different physical connector.
This double pumping technique has been used in all following generations of DDR RAM. It also means that the advertised speed is the transfer rate rather than the clock speed. If you go in-depth enough into overclocking, you can adjust the performance settings of RAM.
You’ll find that one of the settings you change is the clock speed, not the transfer rate. This can lead to confusion, as it is half the speed you might expect if you don’t realize the difference. Additionally, all DDR timings are also related to the clock speed in MHz, not generally referred to as transfer rate.
What Are the Differences Between DDR Versions?
DDR RAM offered transfer rates of 200-400MTs (Mega Transfers per Second) depending on the clock rate, again noting that the clock rate (MHz) is half of the transfer rate (MTs).
DDR2 was standardized in 2003 and doubled the speed of the data bus. Allowing for twice the bandwidth at the same latency, or half the latency at the same bandwidth as the first generation of DDR. The supported transfer rates were between 400MTs and 1066.66MTs. Bandwidth started at DDRs 3200MBs and peaked at 8533.33MBs. Technically the standard supported up to 8GB of DDDR2 per DIMM. However, chipset support for this was low, and 2GB DIMMs were by far the most common.
DDR3 was standardized in 2007, and it again doubled the speed of the data bus. Because the same technique to double the speed was used, it also offered twice the bandwidth at the same latency or the same bandwidth at half the latency. Transfer speeds were between 800MTs and 2133.33MTs for bandwidths between 6400MBs and 17066.66MBs. Higher capacity modules were also available, allowing for 16GB of DDR3 per DIMM.
DDR4 was standardized in 2014 and bucked the trend by not changing the data bus speed. Instead, it focused on increasing the command rate. This means that DDR3 RAM with the same listed speed as DDR4 RAM has precisely the same performance characteristics. However, there was only minimal overlap at the higher end of DDR3 speeds and the lower end of DDR4. Transfer speeds are between 1600MTs and 3200MTs for bandwidths between 12800MBs and 25600MBs. Higher capacity modules were also standardized, up to 64GB per DIMM.
DDR5 is the latest DDR standard. It was standardized in 2020. Speeds have again been doubled, though this time by providing two narrower channels to each DIMM. Transfer rates vary between 3200MTs and 7100MTs for bandwidths of 25600MBs to 57600MBs. Consumer drives are still limited to 64GB per DIMM. However, server DIMMs support up to 512GB per DIMM. Currently, this standard is only just reaching the market, with limited availability and support. However, that will increase in the future.
Should You Upgrade?
Upgrading depends on your situation, though you typically don’t have much choice. No DDR version has been compatible with its predecessor. The voltages, command signals, pin counts, and DIMM keying have all been different. Suppose you are simply considering upgrading your RAM and keeping the rest of the computer. In that case, you will not be able to upgrade to a newer generation of RAM. You may, however, be able to get faster versions of your currently supported DDR generation.
Suppose you’re upgrading your whole computer, i.e., a new motherboard and CPU. In that case, the new setup may require a RAM upgrade. A motherboard will only ever support one generation of RAM. So check which DDR generation you need.
It’s worth noting that upgrading to a new generation of DDR memory as soon as it comes out isn’t generally recommended. Historically, performance is relatively low for the first year or two as the manufacturing process and optimizing memory controllers are improved. Additionally, prices are often higher of a so-called early adopter tax.
Other Types of DDR Memory
Desktop computers take RAM in DIMMs (Dual In-line Memory Module). Though these are often called RAM Sticks, they are generally easy to swap in and out with minimal effort, though the computer would need to be powered off.
Laptops typically use the small form-factor SODIMM (Small Outline Dual In-line Memory Module). These are also able to be swapped out. However, some laptops, especially thin and light models, tend to solder the RAM chips directly to the motherboard. Making it impossible to upgrade them to faster speeds or higher capacities.
GPUs use GDDR as VRAM, while GDDR is based on the same technologies as DDR memory, it differs significantly and is incompatible. GDDR memory is exclusively used on graphics cards and is soldered as close to the GPU die as possible to minimize latency.
DDR memory has been the standard for computer RAM since the turn of the century. Over five generations, it has offered increased bandwidths and capacities. Each generation has been an immediate improvement from the previous generation. There have been some but relatively small amounts of overlap in supported bandwidths.
However, no two generations are compatible. Additionally, motherboards and – at least most – CPUs only support one generation of DDR memory, so unless you upgrade your entire computer, your memory choice is limited to speed, timings, and capacity, not generation.
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