AMD Brings Zen 4c To Laptops With The Hybrid Ryzen 5 7545U, Based on Phoenix 2

hero amd ryzen 7000 series mobile
If you pay attention to hardware news websites like ours, then AMD's Phoenix 2 processor may not need any introduction at all. The chip has already quietly made its debut in the ASUS ROG Ally's cheaper "non-Extreme" edition, and we've talked about it quite a bit elsewhere, as well.

Today, AMD is giving Phoenix 2 a proper introduction with the new Ryzen 5 7545U CPU. We might not normally write up a post about a single new CPU being launched, but this one is pretty special, as it marks the first official launch of an AMD processor that sports two different types of cores.

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Annotated AMD Phoenix 2 die shot by @BusAlexey on Txitter.

That's right: the Ryzen 5 7545U is based on the "Phoenix 2" die that comes with six CPU cores. Two of these processor parts are standard-density Zen 4 CPU cores, while the other four are high-density Zen 4c cores like you'd find in one of the company's EPYC Bergamo server chips. That does technically make this a hybrid CPU design, but as AMD is quick to point out, it's not really at all similar to the way Intel does things.


AMD points out the differences in the approaches with this handy-dandy chart. Where Intel's 12th-gen and later CPUs have compute cores that originate from two different processor families, Zen 4 and Zen 4c are fundamentally identical in terms of capabilities. They support the same instruction sets, they both support simultaneous multi-threading (SMT, known as Hyper-Threading in Intel land), and there's no need for specialized scheduling hardware as a result.

zen4 vs zen4c chart

In that case, what's the point? What's the difference? Well, thanks to its higher density, Zen 4c is more efficient at lower power envelopes than the full-fat Zen 4 core. However, for the same reason, it becomes less efficient at higher power envelopes, meaning it doesn't clock up as well. AMD's research apparently showed that the combination of two standard Zen 4 cores with four Zen 4c cores was "the ideal combination of performance and efficiency."

ryzen 7040u series

So today, AMD's launching the new chip and making a little bit of a revelation about another. The Ryzen 5 7545U slots in adjacent to the Ryzen 5 7540U that the red team announced way back at CES. That chip was based on Phoenix and had six Zen 4 CPU cores that topped out at 4.9 GHz, 22MB of combined L2 and L3 cache, and a TDP configurable between 15 and 30 watts. The new chip has exactly the same specifications, but is based on Phoenix 2 silicon instead of the original recipe, and as it happens, the Ryzen 3 7440U will also be based on Phoenix 2.

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ASUS benchmarks comparing Ryzen Z1 (PHX2) vs. Ryzen Z1 Extreme (Phoenix).

One detail that AMD didn't clarify for us had to do with the integrated graphics of the Ryzen 5 7545U. It's marked down for the same Radeon 740M graphics as the Ryzen 5 7540U. Those chips only have four of Phoenix's twelve RDNA 3 compute units enabled, and that happens to be the number of RDNA 3 compute units available on Phoenix 2. As such, we expect (but can't yet confirm) that the graphics performance will be fundamentally identical between the old and new SKUs.

amd zen4c scalability efficiency

Rumors have indicated for a while that AMD's next-generation hardware would implement a hybrid design similar to Intel's, but in its presentation to us, AMD was coy about the possibility of Zen 4c finding its way into premium SKUs in the future. We fully expect any future hybrid designs from AMD to feature fully-compatible CPU cores that simply differ in density.