AMD RDNA 3 appears primed for 3D V-cache integration
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With the announcement of AMD Ryzen 7000X3D series chips at CES 2023, a lot of attention has been paid to what the new stackable cache technology can bring to Zen 4 processors. According to another teardown of the Radeon RX 7900 XT, there’s reason to hope that the same tech will make its way to a graphics card near you.
What else can you see? A linear series of “spots” remarkably similar to the keep-out zones on X3D, and located at the same 17-18 um pitch. Could they consider stacked MCD functionality (or maybe it’s something else)?January 27, 2023
Tom Wassick, a self-proclaimed “semiconductor packaging engineer”, broke off the new Radeon RX 7900 XT (opens in new tab) to take a deep dive into its innards using infrared imaging. He says the same sort of 3D V-cache connections used for the AMD Ryzen 5800X3D exist on the Radeon RX 7900 XT’s MCD chip, though there’s a blank piece of silicon where a compute-capable die might go.
It is not clear that this type of connection is specifically for 3D V cache, such as Tom’s hardware (opens in new tab) points out, but that’s all AMD has announced for its chiplet stacking technology so far.
AMD has long been rumored to be bringing 3D V cache to its GPUs after successfully implementing it in its Ryzen 5800X3D processor, as well as the upcoming Ryzen 9 7950X3D, Ryzen 9 7900X3D, and Ryzen 7 7800X3D due out in February.
What would 3D V cache even do for a GPU?
The idea behind V-cache is to use a hybrid connection technique to place a chunk of cache memory on top of a processor’s computing cores. This can greatly increase the amount of cache available, saving the processor critical clock cycles because it does not have to go further into regular memory to fetch data or instructions.
In terms of a computer’s CPU, this provides a massive increase in gaming performance, but it’s not clear that such a performance boost would be achieved with GPU cache, though some improvement is likely to occur.
Another issue, however, is thermal performance, an especially important consideration for a graphics card. With 3D V-cache, the extra cache layer on top of the processor cores makes cooling more difficult. AMD may need to lower clock speeds to compensate, which could negate the gain that extra cache could provide.
We probably won’t see these developments in mainstream Radeon cards this year, but we would expect them to drop during midcycle refreshes in cards like the RX 7950 XT or the RX 7650 XT, probably sometime in late 2023 or early 2024.