AMD’s hybrid APUs are lastly official, however they don’t seem to be shifting the needle a lot

It was solely not too long ago that AMD lastly made the launch of its first hybrid processor, colloquially (however not formally) named Phoenix 2. This APU options two common Zen 4 cores and 4 area- and power-efficient Zen 4c cores, for a grand whole of six cores. Intel beat AMD to the punch with hybrid structure, with Lakefield in 2020 as a proof-of-concept and Alder Lake in 2021 as the true deal. Now, AMD has caught as much as its rival and shall be making hybrid processors for the foreseeable future.

The factor is, AMD’s method to hybrid CPUs could be very totally different from Intel’s, and on a per-core foundation they don’t seem to be going to shake issues up practically as a lot as Alder Lake and Raptor Lake. Zen 4c is nearly an identical to Zen 4, and whereas there are benefits to this, in the end it means swapping out some Zen 4 cores for 4c will not make an enormous distinction in efficiency or effectivity. For AMD, the true advantage of hybrid structure is in manufacturing, and that is the factor which may open the door for some actually new AMD CPUs.

What AMD’s first hybrid processor seems to be like

Though AMD’s hybrid APU is a special chip than the unique Phoenix APU that launched earlier this 12 months, its official codename is Phoenix. For the sake of avoiding confusion, I will be calling this hybrid APU Phoenix 2, which is what the PC fanatic neighborhood named it when it first leaked out earlier this 12 months.

That being stated, Phoenix 2 is principally only a smaller Phoenix and is not completely brand-new. It has two fewer CPU cores, eight fewer GPU cores, and is bodily smaller. It additionally lacks Ryzen AI functionality and has a barely smaller L2 cache, although that is solely as a result of it has fewer cores. However in any other case, they’re constructed on the identical TSMC 4nm course of, use the identical structure, and have the identical quantity of L3 cache.

What’s notably attention-grabbing is that Phoenix 2 is a single-CCX design. In Zen CPUs, the CCX is a bunch of cores and is the smallest constructing block, slightly than particular person cores. Whereas AMD has beforehand made two-core, four-core, and eight-core CCXs, Phoenix 2 marks the primary time AMD has made a six-core CCX, and going with one CCX means higher core-to-core latencies. However that is not simply an attention-grabbing tidbit, it is very essential for the way forward for hybrid Zen CPUs since AMD would not introduce new CCX designs fairly often on the subject of core rely.

This all means the ratio of regular Zen cores to dense Zen cores might be going to be 1:2 for some time, because it’s unlikely AMD will substitute the six-core CCX till it is a minimum of a few generations previous. The upcoming Strix Level APU is rumored to be a 12-core chip, which suggests two six-core CCXs. It is extremely unlikely that future APUs constructed with the six-core CCX will supply greater than 12 cores, since extra CCXs imply worse core-to-core latencies. If AMD desires to alter the 1:2 core ratio or supply extra cores per CCX, it must introduce a brand new CCX, however that’s actually years down the road.

How Phoenix 2 compares to Intel’s hybrid CPUs

AMD has taken care to notice all of the variations between its hybrid designs and people of Intel’s. AMD’s hybrid chips will use cores that do not differ architecturally, have the identical IPC, have SMT/Hyperthreading throughout all cores, and do not require complicated scheduling. These are all issues that Intel’s present Raptor Lake chips wrestle with, as the corporate’s P-cores and E-cores are architecturally totally different, whereas Zen 4 and 4c are an identical. Nonetheless, what Intel CPUs hand over in these points, they achieve in others, and that is simply as true for AMD’s hybrid APUs.

The one distinction between Zen 4 and 4c in efficiency and effectivity is that Zen 4 can hit larger clock speeds, and that is a double-edged sword for AMD. It in the end implies that including Zen 4c cores into the combo would not actually change the efficiency or effectivity traits when evaluating Phoenix 2 to a cut-down Phoenix chip. AMD even admits this fairly plainly in its presentation about Phoenix 2, and though Phoenix 2 is extra environment friendly than Phoenix at decrease TDPs, it is a very minor distinction that AMD may have achieved with Phoenix simply by tweaking the frequency per core.

Supply: AMD

In contrast, Intel’s P- and E-cores use totally different architectures to supply totally different energy and efficiency profiles, with the previous providing excessive single-threaded efficiency and the latter nice multi-threaded efficiency in nice numbers. The most important tradeoff AMD is making is counting on a single core structure to at all times meet its efficiency and effectivity wants. If Intel wants better single-threaded efficiency in its subsequent CPU, it simply must deal with redesigning the P-cores and may merely depart the E-cores alone, as an example.

Moreover, Intel’s present era Gracemont E-cores supply a a lot smaller footprint and better efficiency density, similar to Zen 4c towards Zen 4. The truth is, Gracemont cores are smaller than Zen 4c cores regardless of being a era behind node-wise, however after all Gracemont is way slower than Zen 4c.

It isn’t so simple as AMD makes it out to be with its hybrid CPU design, and Zen 4c actually would not change a lot on the subject of efficiency and effectivity. However that is the factor, Phoenix 2 is not actually about efficiency and effectivity, however slightly one thing else.

For AMD, hybrid design is about manufacturing

The important thing advantage of Phoenix 2 and different hybrid Ryzen APUs shall be in manufacturing. Zen 4c’s extra compact measurement means smaller processors, that are clearly cheaper to fabricate than bigger ones. AMD clearly wished to develop a smaller Phoenix APU for lower-end gadgets, however with out Zen 4c it could not have been so small until it solely used 4 Zen 4 cores, which might have resulted in a lot worse efficiency. Hybrid cores enable AMD to supply the identical efficiency for a lower cost, or to pocket the distinction and earn more money.

Whereas it is a profit Intel additionally will get with its method, AMD is unquestionably investing far fewer assets by conserving issues easy. Value-effectiveness has been AMD’s motif ever because it launched the primary Zen CPUs in 2017, and its hybrid APUs proceed that custom. It will likely be attention-grabbing to see if AMD’s method in direction of hybrid design proves to be as profitable as chiplets, an idea that Intel is now following with processors like Meteor Lake and Ponte Vecchio.

Moreover, we do not know if AMD is planning on bringing hybrid design to chiplet-based Ryzen CPUs. Theoretically, AMD may mix an ordinary eight-core Zen chiplet with a 16-core C-type Zen chiplet (which is presently unique to the datacenter) and simply create a 24-core CPU, which can be interesting to AMD since desktop CPUs have been caught at 16 cores since Ryzen 3000. Such a CPU would have a triple-CCX configuration, nevertheless, and it is unclear if it will work effectively and even work in any respect. We’ll all have to attend and see.