AMD, which has already taken advantage of the smaller, optimized Zen 4c cores in its EYPC server CPUs, is bringing its latest technology to the budget notebook world with two new Ryzen APUs that feature up to four Zen 4c cores next to two Zen 4 cores. These compact cores are not AMD's version of the Efficient cores introduced in Intel's Alder Lake hybrid architecture, but AMD is confident you won't notice a difference between the two.

Until recently, the processing cores within any AMD CPU or APU were exactly the same: from the massive 64-core EPYC 7742 to the tiny 4-core Ryzen 3 7440U, each used the same chip to handle all the number crunching. AMD's Zen 4 design Everything changed with the release of Zen 4c, an optimized version of the Zen 4 design, with a 34% reduction in die space requirements

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Initially used only to develop a megacore CPU dedicated to the cloud server market, codenamed "Bergamo," it is now being used to make entry-level laptop APUs even more compact and energy efficient. At this time, only two Zen 4c models are on the market: the six-core Ryzen 5 7545U and the four-core Ryzen 3 7440U. [These will replace the current Ryzen 5 7540U and Ryzen 3 7440U, but since they do not appear to be used in laptops on the market, no one should be disappointed that they missed out on the new technology. The number of cores and clock frequencies remain unchanged, but what is new is that the 7545U splits the Zen 4 and Zen 4c cores 2+4, while the 7440U splits them 1+3.

As AMD stated in a recent briefing, "humans will not be able to tell the difference." This is because Zen 4c is identical to Zen 4 in every way. The operating system, applications, and games work the same way. The new core design retains all the same parts as before, just laid out on a die in a more compact format.

However, squeezing logic units together and shrinking data paths is not without some cost, and in the case of the Zen 4c, these cores cannot reach the same peak clock frequencies as those in the Zen 4. AMD is also working on a CCD (Core Complex Dies) to further reduce the size of the L3 cache by half. [But in the case of these monolithic mobile chips, AMD has already cut the L3 cache in half in order to squeeze Zen 4 into a smaller die. In other words, both the mobile Zen 4 and mobile 4c cores have the same 16 MB of L3 cache, while the desktop chiplet CCD has 32 MB of L3 cache built in.

So what does one gain by using the Zen 4c? Quite simply, the chip is much smaller and requires less power to operate. For laptops, it should be a little cooler when running under load, and battery life should improve as well; AMD is adamant that the performance difference at both ends of the power scale used by laptop CPUs is too small to notice or even matter

They are also keen to point out that Zen 4c is not the equivalent of Intel's E-core; as used in Alder Lake and Raptor Lake CPUs, Intel's Efficient core is much smaller in size than the usual Performance core Although smaller, they perform poorly, especially in games; AMD says the new Zen 4c APUs do not, with all cores accessing the same L3 cache and the same instruction rate per clock.

Neither of these low-end processors is a gaming powerhouse, as they both feature Radeon 740M integrated GPUs, with only four RDNA3 compute units and a total of only 256 shaders.

The scheduler built into Windows and other operating systems does not require additional hardware support to properly assign threads to the appropriate cores. Essentially, the chip uses the existing system already utilized by Ryzen processors to ensure that threads are placed on the most appropriate cores.

In the case of the Zen 4 + Zen 4c chips, intensive, high-demand threads, so-called "bursty workloads," are preferentially (but not exclusively) assigned to the standard core.

Confusingly, the original 7540U and 7440U chips will still be brought to market at some point. Especially vendors who want to make low-power, ultra-portable notebooks.

What was interesting about this announcement is that Zen 4c technology is already used in AMD's Z1 processor. The specifications of that Z1 are nearly identical to the Ryzen 5 7545U, which strongly suggests that AMD has simply rebranded the chip that is found in many portable gaming PCs, such as the Z1 Extreme and Ryzen 7 7840U.

We asked AMD if there was any difference in clock speed between the Zen 4 and Zen 4c cores in these APUs, as it was not made clear in the announcement, but past estimates suggest that the Zen 4c core is designed for lower clock speeds.

On the other hand, consider the fact that AMD is also open to the possibility of using Zen 4c in more premium models; it is unlikely that AMD is talking about replacing chips like the Ryzen 9 7950X with chips with more cores, but rather laptop product line, or perhaps they are talking about semi-custom chips for consoles or handheld PCs.

Take for example the APU used in the PlayStation 5. It consists of an 8-core Zen 2 custom CPU running at up to 3,500 MHz, but a 30% smaller chip based entirely on the Zen 4c should have no problem reaching the same clock frequency. and the advantage for us is the reduction in power consumption.

In theory, a 100% Zen 4c CPU would not require as much power as the current PS5 CPU, which could help AMD and Sony co-design a new APU for the PS5 Pro with a more powerful GPU built in. AMD has been working on an entry-level Ryzen 5 APUs with only Zen 4 cores "doesn't make sense," and the same could be said for many custom chips.

Increased power efficiency would be especially welcome in the handheld PC space, where power limitations are tighter than in full-size gaming consoles. If the gaming performance of the pure Zen 4c chip is acceptable on these platforms, perhaps an updated Z1 chip could appear next year.

It is still early days for the compact version of Zen, but one thing is certain: AMD has done a great job of keeping the CPU market fresh and moving forward, but AMD is not the only chip company with hot new technology. Intel's multi-tiered Meteor Lake is just around the corner, and Qualcomm's striking-looking Snapdragon X Elite is slated to appear in low-power notebooks next year.

The game is just getting started.