AMD 3D V-Cache offers an improved Bandwidth with a Minimal Latency Increase

Chips and Cheese put AMD's EPYC 7V73X (Milan-X) processor with 3D V-Cache to the test. Because this is the same technology that will be used in regular Ryzen processors, the…

By Nivedita Bangari

January 17, 2022

3 min read

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Chips and Cheese put AMD’s EPYC 7V73X (Milan-X) processor with 3D V-Cache to the test. Because this is the same technology that will be used in regular Ryzen processors, the results are likely to foretell the improvements we may expect from chips like the Ryzen 7 5800X3D.

The remaining Chips and Cheese studies demonstrated that 3D V-Cache had a negligible effect on cache and memory latency. The increase resulted in three to four more cycles of delay, according to EPYC 7V73X statistics. Given that the EPYC 7V73X (768MB) has up to three times the L3 cache of the EPYC 7763, this is quite astounding (256MB). While Milan-X has slower clock speeds than Milan, it boosts faster, offsetting the latency increase caused by 3D V-Cache, according to the journal.

AMD’s 3D V-Cache, which has been in the works for a long time, allows the company to stack extra L3 cache on its Zen 3 CPUs. The 3D V-Cache chiplet is bonded to the top of the core complex die (CCD) via a hybrid bonding method. As a result, AMD is currently able to install a single layer of stacked L3 cache on their Ryzen processors. However, because the technique allows for numerous dies, future consumer Ryzen processors could have massive quantities of L3 cache.

The L3 cache on the Ryzen 7 5800X is 32MB. However, because each 3D V-Memory chiplet can hold up to 64MB of 7nm SRAM cache, the Ryzen 7 5800X3D has a total L3 cache of 96MB, which is triple that of the Ryzen 7 5800X. As a result, the Ryzen 7 5800X3D’s base and boost clocks are 400 and 200 MHz lower, respectively, than the Ryzen 7 5800X. If Chips and Cheese’s test is correct, the Ryzen 7 5800X3D’s greater L3 cache should mask its slower clock speeds.

AMD demonstrated at CES 2022 that the Ryzen 7 5800X3D had 15% better 1080p gaming performance than the conventional Ryzen 9 5900X. In another figure, the Ryzen 7 5800X3D outperformed Intel’s latest Core i9-12900K, and in some cases even outperformed it.

The 3D V-Cache chiplet from AMD is stacked on top of the CCDs. Because the Ryzen 7 5800X only has one CCD, its L3 cache is limited to 96MB (32MB + 64MB). Ryzen SKUs with two CCDs, such as the Ryzen 9 5900X, can have up to 192MB. The maximum memory capacity of the Milan-X, which has up to eight CCDs, is 768MB (256MB + 512MB).

At Computex 2021, AMD promised a prototype Ryzen 9 5900X with 3D V-Cache but made no mention of it at CES 2022. As a result, it’s unclear whether AMD will release the Ryzen 9 5900X3D or Ryzen 9 5950X3D.