AMD presented yesterday the first models of CPUs for laptops based on its new Zen 3 core, the 5000HX models, but these not only bring the new AMD CPU architecture, but also bring a significant increase in cache. What are these changes and what do they mean for the performance of these AMD CPUs?
If AMD became the queen of desktop performance a few months ago with the Ryzen 5000, now with the ones just presented at its CES conference, the Ryzen 5000HX, AMD has taken the lead in laptops and for this they have made changes that go beyond the adoption of the Zen 3 core.
Four times the L3 cache in the AMD Ryzen 9 5000HX
Last year when AMD launched its monolithic version in both SoC and CPU of its Zen 2 cores , these came with a major cut and that is that the amount of L3 cache per CCX had been reduced from 16 MB of the chiplet-based versions to only 4 MB, something that the next generation video game consoles have also inherited in their custom SoCs.
With Zen 3 there have been two important changes, the first one is that now each CCX is 8 cores and the second is the increase in the IPC in the processor, but if we talk about the AMD Ryzen 5000HX there has been a second change and it is the increase in the amount of L3 cache available to the processor.
Joining the two quad-core CCXs into one eight-core also adds the caches, causing each core to have twice as much L3 cache available as before, but the Ryzen 5000 Mobile do not have 8MB of L3 cache but 16MB , quadrupling the ratio compared to the previous generation.
What are the advantages of increasing the L3 cache in the AMD Ryzen 5000HX?
To begin with, we must bear in mind that in all Zen architectures, from Zen to Zen 3, the L3 cache is a “victim cache”, which is responsible for collecting all the cache lines discarded by the L2 cache, it is not part of the process of capturing data and instructions as a conventional last level cache would do, since although the data passes through the communication infrastructure between the L3 cache and the SDF / Northbridge in the direction of the former, it is not stored in said cache.
But the increase in the capacity of the “victim cache” prevents a large number of lines from ending up in memory, this means that if a CPU core needs to access memory again, it does not need to go to RAM and can consult in this case to the L3 cache. This is very important in systems that depend on consumption such as laptops, since the closer a data is, the fewer parts of the processor are activated and therefore the energy consumption is lower.
Is it going to be a trend in the rest of the Ryzen 5000 Mobile?
In principle there should be no change in the amount of cache for the AMD Ryzen 5000H and the AMD Ryzen 5000U with respect to the AMD Ryzen 5000HX, remember in passing that some models of the Ryzen 5000U were based on Zen 2 and not Zen 3, so they would not benefit from this increase in third-level cache.