Introduction

The much talked about Intel 12th Gen Core "Alder Lake" processors made landfall last week and are shaking things up in the processor world right now. Be sure to catch our comprehensive reviews of the three (12900K, 12700K, 12600K). Alder Lake is the first client architecture to support next-generation DDR5 memory, which we've used in our main reviews of these processors.

The new memory standard generationally doubles memory bandwidth, density, lowers DRAM voltage, improves efficiency, and introduces new features, such as on-module power-management, intrinsic ECC, and more. All this comes with a heavy early-adopter tax—some of the first DDR5 memory kits are going for at least 50% more than DDR4. This makes DDR5 a tough sell at a time when other hardware is already priced on the boil. What's great is that Intel isn't forcing DDR5 on us with Alder Lake; instead, they designed their new processors as a transitional architecture supporting the new DDR5 and older DDR4 memory.



In addition to support for DDR4 memory, Intel ensured that its motherboard partners actually do launch a fairly broad selection of Intel Z690 chipset motherboards with DDR4 support. The company reportedly prohibits them from coming up with boards that have both DDR5 and DDR4 slots for whatever reason. It's also rumored that the next-generation Core "Raptor Lake" processor will retain DDR4 support, so those investing in a DDR4 motherboard to keep using their older memory are set for at least another generation of processor upgrades.

The 12th Gen Core Alder Lake processor supports up to 128 GB of memory. For DDR5, the processor supports a total of four 40-bit wide memory channels (two 40-bit channels per DIMM, with 8 of those bits being used for ECC), and for DDR4, it supports dual-channel; i.e., two 64-bit wide memory channels (64-bit channel per DIMM), just like older generations of Core processors, dating all the way back to 6th Gen Core "Skylake." The unlocked "K" or "KF" processors launched thus far feature native support for DDR5-4800 and DDR4-3200. This is the official baseline specification; the processors are able to handle much higher memory clocks, of course.

Also featured is the new XMP 3.0 standard, an Intel-designed DIMM SPD extension that makes applying a memory vendor's advertised memory clock speeds and latencies as easy as two clicks in the UEFI setup program. You can also use the Intel Xtreme Tuning Utility (XTU) to apply XMP profiles, or overclock your memory on-the-fly (a feature exclusive to the Intel platform). XMP 3.0 introduces support for up to five profiles per DIMM, including two user-defined ones, and longer 16-character labels for each profile.

Much like the 11th Gen Rocket Lake, Alder Lake comes with "Gear" Ratios for memory overclocking. "Gear 1," the default, runs the DRAM data bus at DDR, twice the DRAM clock frequency, and the command bus at the DRAM clock frequency. When you enable "Gear 2," the data bus speed is unchanged, still DDR, but the command bus ticks at half the rate of the DRAM clock frequency. While that obviously means the memory controller can only execute commands at half the speed of Gear 1, the actual data transfer rate remains unchanged. Gear 2 provides stability at higher memory clocks by clocking down the command bus and memory controller, which introduces the ability to run the MC+DRAM combination at higher DRAM clock frequency.

As we mentioned earlier, DDR5 memory introduces a generational doubling in memory clocks, which should on paper mean a doubling of the memory bandwidth available to the processor. These increased frequencies, however, also come with higher latencies. As such, it'll be interesting to find out just how much performance is lost if you choose to keep your DDR4 memory, and whether there's a point at which DDR4 can reach or surpass DDR5 frequency. In this review, we are testing the Core i9-12900K processor in 37 application tests and 10 games, with four DDR4 memory configurations, and compare it to our DDR5-6000 baseline results.

Test Setup

Other test systems are the same as in our Core i9-12900K review.