AMD has expanded its series of mobile processors Ryzen 7040U, adding the Ryzen 5 7545U model to the lineup and Ryzen 3 7440U with a hybrid layout, which for the first time combines computing cores with Zen 4 and Zen 4c architectures.
Such a conventionally “heterogeneous” combination is partly reminiscent of Intel’s approach, which uses performance (P-cores) and energy-efficient (E-cores) cores for its processors. However, despite the initial similarities, AMD is guided by a different approach. Developers are trying to maximize energy efficiency and reduce the area of the processor chip, while obtaining high performance when there are no power consumption restrictions.
First of all, it is worth noting the dimensional achievements. In the case of Zen 4c, the area of one computing core with L2 cache was reduced by about 35% – from 3.84 mm² to 2.48 mm². That’s quite a bit of “compression” in the context of TSMC’s identical 4nm process. How does such a reduction affect performance? Due to the denser packaging of the blocks, the maximum frequency is slightly reduced, but the cores can operate at a lower operating voltage.
Now let’s take a look at the architectural differences between Zen 4 and Zen 4c. However… Yes, this is not a mistake on AMD’s slide, there really is no functional difference. And this is the main difference with Intel’s approach, which uses heterogeneous P/E-cores.
Given the architectural identity of the Zen 4 and Zen 4c cores, it is easy to assess the features of solutions based on them, but in its presentations AMD makes certain emphases comparing the situation with the approach of its main opponent. All processor cores have identical instruction sets, the same IPC, and support multithreading. At the same time, there is no need for an additional mechanism for scheduling tasks depending on the load (a hint of Intel Thread Director).
The new Ryzen 5 7545U and Ryzen 3 7440U chips belong to the Phoenix 2 family. The older 6-core model has the following layout – 2 Zen4 cores + 4 Zen4c cores. Since the functional computers are identical and support SMT, the processor can simultaneously process up to 12 data streams. All cores have 1 MB of L2 cache and 16 MB of L3 cache, so the total L2+L3 capacity is 22 MB. As for the operating frequencies, AMD goes to some tricks, indicating in the specification only the general limit values of 4.9/3.2 GHz. Obviously, these are the figures for the “large” Zen 4 cores, while the more compact Zen 4c has a more modest frequency range. For some reason, the developers have not disclosed this data yet. The U-series chips are generally quite economical processors, so the power consumption level is configurable within 15-30 watts. The processor is equipped with integrated Radeon 740M graphics with four clusters that include 256 computers in total.
If you pay attention, these specifications are identical to those for the previously introduced representative of the first wave of the Phoenix line – Ryzen 5 7540U, which has 6 Zen 4 cores, the same frequency formula and TDP level.
In such circumstances, the question of the logic of processor labeling and the ease of interpretation of model names by users immediately arises. In this case, the increased index may not quite correctly orient a potential buyer regarding CPU performance. However, we will return to this point later.
The junior Ryzen 3 7440U model was announced back in the spring, along with the first Phoenix chips, but as it turned out, the actual release of the processor was delayed, and the CPU itself became a carrier of a hybrid layout. So, Ryzen 3 7440U is a 4-core 8-thread processor with 1 Zen 4 core and 3 Zen 4c cores. This is a rather interesting asymmetrical configuration. The chip is equipped with 8 MB of L3, and the total L2+L3 capacity is 12 MB. Like the older model in the Phoenix 2 line, the chip is equipped with integrated Radeon 740M graphics. The question of the name also arises, as the current model designation does not allow identifying the use of a combination of Zen4+Zen4c cores.
The next slide with the performance evaluation of Ryzen 5 7540U and Ryzen 5 7545U depending on the power consumption level allows you to better understand the nuances of the new CPUs with a combined core architecture. As you can see, the Ryzen 5 7540U model, which uses six Zen 4 cores, has slightly higher performance with chip power consumption of more than 20 watts. At the same time, the Ryzen 5 7545U with a hybrid layout of 2 Zen4 + 4 Zen4c starts to come out ahead at 17.5 watts and with a 10-watt limit has a maximum advantage over the Ryzen 5 7540U during a multi-threaded Cinebench load. Therefore, chips with Zen4c are primarily a story about energy efficiency with low power consumption.
After today’s announcement, there is no doubt that Ryzen Z1 processors for portable gaming consoles also use a combined architecture with Zen 4 + Zen 4c cores. Moreover, judging by the updated specification on AMD’s website, Ryzen Z1 actually has the same characteristics as Ryzen 5 7545U. With the exception of an even wider TDP tuning range of 9-30 W.
As a reminder, the older Ryzen Z1 Extreme model has much in common with the top chip in the Ryzen 7040U series, the Ryzen 7 7840U. For cases where maximum performance is required, the Zen 4 is certainly a favorite.
Why do you need Zen 4c if you have Zen 4?
- Reducing the size of computing cores without reducing performance per cycle (IPC) makes it possible to increase the overall performance of processors by scaling the number of computers. This is especially important for server CPUs, where the introduction of compact Zen 4c cores was initially launched. The same EPYC chips of the Bergamo family already offer up to 128 cores on a single textolite substrate. Isn’t that a miracle?
- The compact dimensions of the computing cores allow to reduce the area of the processor chip, thereby reducing the overall cost of manufacturing the CPU. Recall that the Phoenix family of processors uses a 178 mm2 silicon wafer, while the new Phoenix 2, which combines Zen4 and Zen4c, uses 137 mm2 wafers. Although it should be borne in mind that the Phoenix has 8 Zen 4 cores and Radeon 780M graphics with 12 computing modules. Whereas Phoenix 2 has 6 cores (2+4) and Radeon 740M with 4CUs. Therefore, the impact of the more compact Zen4c cores on the overall dimensions in this case is more modest, but it is also there.
- The ability to combine Zen4 cores with the more compact Zen 4c cores adds flexibility to developers, allowing them to offer custom solutions with good performance and low power consumption. A good example is the emergence of quite powerful Ryzen Z1 for gaming consoles.
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