With the announcement of the AMD Ryzen 7000X3D series chips at CES 2023, much attention has been given to what the new cache stacking technology could bring to the Zen 4 CPUs. According to the new Radeon RX 7900 XT breakup, there is reason to hope that this the technology itself will go to the graphics card nearby.
What else can you see? A linear arrangement of “dots” that look remarkably similar to the protection zones in X3D and that are all at the same 17-18 um spacing. Can they consider stacked MCD functions (or are they something else)?January 27, 2023
Tom Wassick, self-proclaimed “professional in semiconductor packaging engineering”, demolished the new Radeon RX 7900 XT (opens in a new tab) make a deep dive into its innards using infrared imaging. He says the same kind of 3D V-cache connections as the AMD Ryzen 5800X3D exist on the Radeon RX 7900 XT’s MCD die, although there is a hollow piece of silicon that could house a computation-capable die.
It’s unclear if this connection type is specifically for V-cache 3D because Tom’s gear (opens in a new tab) points out, but that’s the only thing AMD has announced so far regarding chiplet stacking technology.
It has long been rumored that AMD will introduce 3D V-cache to its GPUs after successfully implementing it in its Ryzen 5800X3D CPU, as well as in the upcoming Ryzen 9 7950X3D, Ryzen 9 7900X3D and Ryzen 7 7800X3D due for release in February.
What would a 3D V-cache do for a GPU at all?
The idea behind V-cache is to use a hybrid bonding technique to place a cache block on top of the CPU’s compute cores. This can greatly increase the amount of cache memory available, which saves critical CPU clock cycles as it does not have to reach further into regular memory to fetch data or instructions.
As far as the PC’s CPU is concerned, this results in a huge boost in gaming performance, but it’s not clear if such a performance boost can be achieved with the GPU cache, although there is likely to be some improvement.
Another concern, however, would be thermal performance, especially important for a graphics card. With V-cache 3D, an extra cache block on top of the CPU’s compute cores complicates cooling. AMD may have to lower the clock frequency to compensate, which could nullify any gain the extra cache might provide.
We’re unlikely to see these changes on mainstream Radeon cards this year, but we should expect a drop in mid-cycle refresh on cards like the RX 7950 XT or RX 7650 XT, possibly in late 2023 or early 2024.