It looks like big.little CPU design—an architecture that includes both fast, power-hungry cores and slower, more power-efficient cores—is here to stay in the x86_64 world, according to unverified insider information leaked by wccftech and AdoredTV.
Intel’s big/little designs enter round two
At Intel’s 2021 Architecture day, the company confirmed that its upcoming Alder Lake (12th generation) processors will use a mixture of performance and efficiency cores. This brings the company’s discontinued 2020 Lakefield design concept firmly into the mainstream.
Big.little designs run time-sensitive tasks on bigger, hotter performance cores while running background tasks on slower but much less power-hungry cores. This architecture is near-universal in the ARM world—which now includes Apple M1 Macs as well as Android and iOS phones and tablets—but it’s far less common in the x86_64 “traditional computing” world.
Intel’s Lakefield architecture only lasted one year and only consisted of two products—the i5-L16G7 and i3-L13G4. Market demand was almost nonexistent for Lakefield, likely due to a poor mixture of performance and efficiency cores—both Lakefield CPUs offered only a single performance core, backed by four efficiency cores.
Expected 12th- and 13th-gen SKUs
Alder Lake—Intel’s 12th Core generation, expected in November 2021—will shift the design balance far more heavily to the performance side, with i9-12900K expected to offer eight Golden Cove performance cores and eight Gracemont efficiency cores. The Golden Cove cores support hyperthreading, but the Gracemont cores do not, resulting in lopsided core/thread counts—such as 16 cores/24 threads for the expected i9-12900K.
According to the rumors leaked by AdoredTV, Raptor Lake will build on and expand the Alder Lake design, replacing Golden Cove performance cores with Raptor Cove and enhancing the design of the Gracemont efficiency cores. We’re also expecting core counts to increase from Alder Lake to Raptor Lake, with an expected 24-core/32-thread i9-13900K due in 2022, if all goes well.
Power consumption is one of the key details in most of these rumors, with three major classes of power consumption expected in desktop Alder and Raptor Lake CPUs alike—at 35W, 65W, and 125W TDP. We can take a look at the projected core counts of enthusiast CPUs (all of which are expected to come in at 125W TDP) below, after current-gen Rocket Lake-S CPUs for comparison:
|Rocket Lake-S (11th-gen desktop CPUs)|
|Alder Lake-S (12th-gen desktop CPUs)|
|Raptor Lake-S (13th-gen desktop CPUs)|
Both Alder Lake and Raptor Lake are expected to use Intel’s 10nm process, which the consumer space has so far seen only in mobile CPUs. Rocket Lake-S was originally expected to be built on 10nm but ended up built on Intel’s venerable 14nm process with “backported features” from the 10nm process, which still wasn’t quite ready for (desktop) primetime.
Power and performance
The key takeaway here is that, while Intel is bumping up its core counts significantly, it’s only doing so by adding efficiency cores—the performance core counts are expected to remain unchanged at 6, 8 and 8 for the Core i5, Core i7, and Core i9 families, respectively.
Intel seems to be banking on adding efficiency cores as a way to become a bit more competitive in multi-threaded workloads without repeating AMD’s disastrous mistake in the Piledriver era—that is, attempting to compete on raw performance by creating such a power-guzzling monstrosity that nobody wants to live with it. Of course, this ignores a couple of room-filling elephants.
On the performance side, it seems unlikely to expect an i9-12900K with 16 total cores to compete well with its closest AMD equivalent. A current-generation Ryzen 9 5950x already offers 16 cores—and all 16 are performance cores. Ryzen 9 5900X comes in at “only” 12 cores—but again, all 12 are performance cores. We’re not sure what Team Red has in store for its next generation yet, but we certainly aren’t expecting core count decreases.
On the power-consumption side, we’re only looking at Intel’s PL1 TDP rating—the TDP necessary to run the chip off turbo. We think it’s too early to give any credibility to PL2 rumors for Alder and Rocket Lake, but we know Rocket Lake-S’ “125W TDP” parts can easily hit 200W or higher when running at turbo frequencies.
Anandtech shows peak TDP of up to 300W for the i9-11900K, with even the i5-11600K coming in at 210W—while AMD’s peak, on-boost power consumption stays below 150W on 12-core Ryzen 9 5900X and 16-core 5950X.
First and foremost, we want to remind everyone that the plural of “rumor” is not “established fact”—nearly all of this reporting relies on data leaked from various sources throughout 2021. We can be certain that Alder Lake and Raptor Lake will use a hybrid big.little design as described—but most everything else is still up for grabs to one degree or another.
We’re reasonably confident that Alder and Rocket Lake-S SKUs will exist with core counts as shown here and that TDP won’t change significantly as compared to Rocket Lake-S. But it’s unclear whether these designs will successfully follow Apple’s M1 in securing the big.little hybrid design’s place in desktop computing history or be relegated to the dustbin like last year’s Lakefield.