It isn't easy for a company to release faster CPUs year after year. But there are two relatively easier ways to go about it. They can increase clock speeds or add more cache. Intel has put a lot of effort into its clock speeds while AMD's focus is on increasing cache. The latter is best illustrated by its claim of a 15% performance gain from its upcoming 5800X3D (opens in new tab) CPU, simply by adding more L3 cache.
Intel’s cache sizes haven't seen anywhere near as large of a jump in recent years. But that could be set to change with its upcoming 13th Gen Raptor Lake CPUs (opens in new tab), though its increases are to come from adding L2 cache rather than L3.
In a initial tweet, (via HotHardware (opens in new tab)) leaker OneRaichu (opens in new tab) stated that "68M cache is interesting.😄" OneRaichu later clarified that he was talking about the total amount of cache packed in to Intel's 13th Generation Raptor Lake CPU.
The cache structure of Alder Lake gets a bit confusing. The full Alder Lake die includes 1.25MB of L2 cache for each of the eight P cores. The two E-core clusters get 2MB of L2 for a total of 14MB of L2 cache. The L2 cache is joined by up to 30MB (3MB per P core and E core cluster) of shared L3 cache which gives a total of 44MB.
According to the rumors, Intel will increase the total amount of available cache from 44MB to 68MB. First we need to bear in mind that Intel is expected to increase the E core count from 8 to 16 which would mean a total of 54MB of L2 and L3 if Raptor Lake kept the Alder Lake cache structure.
To help visualize this potentially confusing bunch of numbers, another twitter user Olrak29_ (opens in new tab) made up a picture to illustrate what the cache structure of a hypothetical i9 13900K could look like.
If the leaks are accurate, Raptor Lake’s L2 cache sizes will increase from 1.25 MB to 2MB for each P core and 2MB to 4MB for each E core cluster. This would mean a total of 32MB of L2 cache for all cores and 36MB L3 cache for all cores. This delivers the grand total number of 68MB.
It remains to be seen just how the extra L2 cache will affect performance. The L2 cache mightn’t look all that big but it offers a lot more bandwidth with lower latency compared to L3. If software is coded to take full advantage, there could be a significant IPC bump. That's something that games will take advantage of.
Of course we’ve hardly gotten over the launch of 12th Gen (opens in new tab), and we’re still many months away from the release of 13th Gen Raptor Lake. We can't wait for the leaks to start. It will be interesting to see how Raptor Lake and Zen 4 processors differ in their cache structures, and what it means for gaming performance.