Intel’s 12th Generation Core processors, code-named “Alder Lake,” just hit the street, and with them begins the Age of DDR5. With the new CPUs come two new technologies that the PC cognoscenti will need to know about either immediately, or eventually: DDR5 memory, and the PCI Express (PCIe) 5.0 bus. The latter is less urgent to absorb; PCIe’s backward-compatibility with previous generations gives the unprepared months or even years to prepare for future transition. But, depending on the PC or Alder Lake motherboard you may buy, the move to DDR5 could be a full-on, do-it-now switch: Boards that use DDR5 won’t support DDR4, and vice versa.
Knowing this, we’re sure you’ll have a few questions before deciding whether or not this is the time to take the leap into unknown memory waters. We still have plenty of questions ourselves, which we’re working out in our first few weeks on this new platform. (Indeed, we just finished our first formal tests of DDR5 versus DDR4 modules.) This guide is designed to make those new waters less intimidating. That’s not to say they aren’t deep, though! Let’s go to the Q&A.
What Is DDR5, and Why Do We Need It?
DDR5 is the newest standard for memory modules on consumer PCs, coming to market in concert with Intel’s 12th Generation Core processors (headed by the Core i9-12900K) and associated Z690-chipset motherboards. Motherboards using the Z690 chipset (and thus with “Z690” in the name) are the the first consumer boards to support DDR5 memory modules and Alder Lake chips.
The drive to develop and debut DDR5 lies mainly with its increased capacity of 64Gb (gigabits) per integrated circuit (or IC, aka the chips on the memory modules themselves). This represents a fourfold increase compared to DDR4. Previous generations of DDR memory have typically doubled capacity compared with their predecessors.
Other improvements, such as its increased (twice-as-high) data rate, could prove beneficial to those trying to extract more performance from integrated graphics on supported processors. But it’s important to remember that DDR4’s capacity limits will linger long after new programs push high-end builders to seek alternative solutions. DDR5 may be young, but it is the future.
How Is DDR5 Memory Different From GDDR5 Memory?
Though the names may appear similar, Graphics DDR5 (GDDR5) is an older, DDR3-based technology that’s designed for graphics cards. While DDR5 main system memory is primarily soldered to removable memory modules, or DIMMs, GDDR5 is soldered directly to graphics cards. Because CPUs and discrete video cards complete different tasks using their own RAM, these pools of memory are treated separately by the system.
What Kind of Per-Module Capacities Can We Expect With DDR5?
The quadrupling of maximum IC capacity brings with it consumer DIMMs of up to 128GB per DDR5 module. The typical four-slot DDR4 desktop motherboard can hold up to 128GB of memory in total (using four 32GB consumer DIMMs, aka “UDIMMs” in industry-speak), but DDR5 expands that to an incredible 512GB on four-slot boards that support that peak amount. And that’s just for typical mainstream, consumer boards.
Also consider High End Desktop (HEDT) platforms. HEDT boards with twice as many DIMM slots even get a terabyte of maximum capacity, which is a greater DRAM capacity than the average consumer SSD! Note: Higher-capacity (64GB) registered DDR4 memory required platform support for special registered memory (RDIMMs), which are typically limited to high-end workstations and servers. In contrast, you’ll have 64GB DDR5 modules available to consumers willing to pony up the bucks.
What Platforms Will DDR5 Work On?
At this late-2021 writing, consumer DDR5 was initially limited to Intel’s new LGA 1700 socket (“Alder Lake”) platform, with separate developments in the data center and server sector focused on registered DIMMs. Expect to see further developments from both Intel and AMD in next-generation platforms.
For now, on the consumer side of the aisle, you’ll see DDR5 memory support on the lion’s share of (but not all) initial motherboards for 12th Generation Core, under the Z690 chipset. Note: Some Z690 boards, however, will maintain support for DDR4. (More on that in a moment.)
Do I Have to Use DDR5 for an Intel LGA 1700 PC Build?
One reason that the Intel LGA 1700 CPU socket has so many more pins than its predecessor (LGA 1200) is that it separately supports two different memory standards. While the design precludes using two different types of memory at the same time, motherboard manufacturers have responded by producing LGA 1700 motherboards in both DDR5 and DDR4 variations.
Let’s clarify that, though. A given motherboard supports DDR5 or DDR4, not a choice of one or the other, or the ability to use both kinds of modules side by side. When you buy a Z690 motherboard, you need to know which memory type it supports: DDR5 or DDR4. DDR5 and DDR4 modules are actually keyed differently, and you can’t stick one in the other’s slots.
What About DDR5 on Laptops? Will There Be DDR5 SO-DIMMs?
DDR5 SO-DIMMs were announced several months ago, running at desktop-spec DDR5 (1.1-volt) voltage levels. New Alder Lake mobile and low-power platforms are expected to launch soon after the desktop platform, but they weren’t here yet at this writing.
LPDDR5 memory at 0.9 volt has also been developed, but guesses regarding which CPU models may require it are exactly that—guesses!—for now.
What Are the Main Differences Between DDR4 and DDR5?
The biggest difference between DDR5 and previous generations is that each 64-bit rank now contains two 32-bit channels. While splitting the 64-bit channel in two doesn’t increase bandwidth, it does allow smaller transfer blocks for its increased (doubled) 16 data-cycle burst length.
Other big changes include on-module voltage regulation, a drop from DDR4’s 1.2-volt internal voltage to 1.1-volt, on-die ECC for single-bit internal errors (more about that later), data rates roughly twice those of DDR4, and latencies of roughly twice as many cycles as DDR4.
That last “advancement” (regarding latencies) appears to indicate slower response times, but since doubling the clock cycles reduces latency time by half, the “lengthier” timings should have minimal performance impact. (We’ve got more on this in our DDR5-versus-DDR4 testing feature mentioned earlier.)
What Advantages Should DDR5 Bring?
In addition to the previously mentioned capacity increase, DDR5 will offer around twice as much bandwidth as DDR4. Since most consumer applications are hardly bandwidth-starved, and those that are typically favor lower latency, the greatest performance gain will likely occur in games, when using integrated graphics.
Is DDR5 More Energy Efficient Than DDR4?
With a mere 0.1 volt separating DDR5 from DDR4 voltage levels, we expect minimal power-consumption changes for a typical PC build. That said, while the touted efficiency effect might seem minimal in the consumer segment, noticeable improvements are likely to occur in systems that employ many modules, such as servers, and rack systems in data centers.
Will DDR5’s On-Die ECC Protect My System From Data Bus Errors?
Unlike the separate error-correction and buffer ICs used to correct transmission errors between the CPU and DRAM of previous-generation memory, the on-die ECC of DDR5 is only meant to address the single-bit errors that are more likely to occur inside a densely-packed IC as the circuits are further miniaturized.
Because this technology does nothing to ensure that the data received by the memory is correct, ECC-buffered DDR5 will be a separate product category sold primarily to workstation and server configurators in the same way that it was with past generations of memory modules. Standard consumer DDR5 won’t be labeled ECC, and it won’t correct bus errors.
Should I Expect to Pay More for Comparable DDR5 Versus DDR4?
That’s a three-part answer. Now: Definitely, yes. In the near term: Yes, but less so than now. Long term: DDR5 will be the only game in town, or at least the mainstream and default choice.
DDR5 is projected to cost 50% to 60% more than DDR4 over the intermediate term (the first two years), but its capacity and bandwidth advantages will eventually make it the prevailing standard. Because part of DDR5’s additional cost is in its on-module voltage control, the only way it could reach cost parity is if DDR4 were in short supply.
That said, at launch DDR5 is selling here in late 2021 at a significant markup versus even those 50% to 60% projections, with stock low everywhere and modules only spottily available. Scalpers have even started to get in on the DDR5 game, like they have for some time with graphics cards and other in-demand electronics. Supply (and pricing) will likely moderate in 2022, but for now, DDR5 is beset by early-adopter and scalper tax.
How Much DDR5 Do I Need? Have Relative Memory Needs Changed From DDR4 to DDR5?
The lowest-capacity DDR5 modules we’ve seen announced have been 8GB, and those are using four 16-bit (rather than eight 8-bit) ICs per rank. That makes 16GB the lowest likely capacity for a dual-channel system. Wide (16-bit) ICs are also usually produced only for the lowest-end modules, so that the least memory you’re likely to find in a performance machine will be 32GB. (For a deeper discussion of memory ranks and their significance, see our comprehensive primer on how to buy the right PC memory.)
Though the use of DDR5 doesn’t affect capacity demand, the increased capacity baseline of performance RAM comes at a time when increases in software complexity are already making 32GB an attractive starting point for high-end builds. We’d expect to see a move from 8GB as the starting point for mainstream systems based on DDR4, to 16GB with DDR5.
Should I Move to a New Desktop Platform Just to Get DDR5?
The best time to upgrade your system is when your old one either fails, or can no longer provide a necessary function, such as when new interfaces are introduced. Meanwhile, the best time to jump into a new technology is usually several months after its release. The bugs get worked out, the first-adopter novelty wears off, and hardware availability aligns across all the parts of the platform to provide far greater value.
Some users will simply want to jump on the Alder Lake bandwagon ASAP; the performance of Intel’s new CPU really is impressive for content creators and PC gamers. And if you want to build or upgrade to a future-proof PC with parts you’ll be able to re-use in a few years, you won’t want to buy into DDR4 modules right about now. While the test results in our early DDR5 trials don’t show a huge amount of difference between closely matched DDR4 and DDR5 machines using the same 12th Generation Core i9 CPU, we have no problem recommending DDR5 to anyone who wants to keep up with the future of the desktop. Just expect to pay big for the bragging rights, for now.
