AMD Instinct MI325X

What the MI325X is

The AMD Instinct MI325X is a data-center accelerator from AMD's Instinct line, announced on 10 October 2024 ^[3]. It is a GPU made for AI workloads: training large neural networks and serving them to users. The part AMD puts first in its description is memory. The MI325X carries 256 GB of HBM3E, a stacked high-bandwidth memory, and moves it at 6 TB/s ^[1].

What is inside

AMD's documentation places the MI325X on the third-generation CDNA architecture, the design family behind its data-center GPUs ^[1]. The chip contains 304 compute units ^[1]. Compute units are the repeated building blocks of a GPU: the work of a kernel is spread across many of them at once, so the number of units is one rough indicator of how much parallel work the chip can take on in a clock cycle. The architecture generation matters as much as the count, because it decides which instructions and data types the hardware can execute efficiently.

Memory and the models it targets

Large language models are limited in practice by how much memory is available to hold weights and intermediate results. AMD says the MI325X is designed to handle models with one trillion parameters ^[1]. A parameter is a learned weight in the network; a trillion of them, at the reduced numeric precision typically used for inference, already amounts to hundreds of gigabytes before any working memory is counted, which is why a 256 GB pool at 6 TB/s is central to the design ^[1].

In its announcement AMD compared the memory directly with Nvidia's H200, stating that the MI325X offers 1.8 times the capacity and 1.3 times the bandwidth of that part, and that production shipments were tracked for the fourth quarter of 2024 ^[3]. Such comparisons are how accelerator vendors position successive generations: capacity decides which models fit on a device, bandwidth decides how quickly their weights can be streamed through the compute units.

How it connects

The MI325X has a 16-lane PCIe Gen 5 host interface and seven Infinity Fabric links ^[1]. The PCIe interface is the standard connection between an accelerator and the host processor; 16 lanes describes the width of that serial link, and Gen 5 is the generation of the PCIe standard it uses. The Infinity Fabric links are AMD's own interconnect for joining accelerators together. In a multi-GPU server these links carry the traffic that keeps several chips working on one job, so their number and speed shape how well a node scales beyond a single device.

Where it sits in the line

AMD later treated the MI325X as one step in a sequence. Its launch material for the MI350 series describes the MI325X as the previous series, repeating the same 256 GB of HBM3E and 6 TB/s of bandwidth ^[2]. The wording matters for how the product should be read: it is a memory-capacity refresh of the generation before it rather than a new architecture, and AMD's own later documentation places it below the MI350 parts that followed.

For buyers, the MI325X sits in the segment where a single device is expected to hold a very large model, or a large slice of one, without splitting it across many chips. Its specification sheet reads as a set of trade-offs around that goal: a large memory pool and wide interconnect on one side, and a compute count and architecture generation that AMD's next series would move past on the other ^[1][2].