In a nutshell: JEDEC has announced the HBM3 standard. And, like any good revision to a memory standard, it features a minor decrease in voltage, a slew of added conveniences, and a doubling of all the performance-related specifications. Bandwidth? doubled. Layers? doubled. Capacity? doubled.

In numbers, an HBM3 stack can reach 819 GB/s of bandwidth and have 64 GB of capacity. In comparison, the HBM2e stacks used by the AMD MI250 have half the bandwidth, 410 GB/s, and a quarter of the capacity, a mere 16 GB.

At eight stacks, the MI250 has a total of 128 GB and 3277 GB/s of bandwidth. Eight stacks of HBM3 would have 512 GB with 6552 GB/s of bandwidth.

Specification JESD238 JESD235C JESD235B JESD235A
Bandwidth (per stack) 819 GB/s 410 GB/s 307 GB/s 256 GB/s
Die (per stack) 16 - 4 layers 12 - 2 layers 8 - 2 layers
Capacity (per die) 4 GB 2 GB 1 GB
Capacity (per stack) 64 GB 24 GB 8 GB
Voltage 1.1 V 1.2 V

HBM3 also doubles the number of independent channels, from eight to 16. And it's introducing "pseudo-channels" that allow it to support up to 32 virtual channels.

According to JEDEC, HBM3 additionally addresses the "market need for high platform-level RAS (reliability, availability, serviceability)" with "strong, symbol-based ECC on-die, as well as real-time error reporting and transparency."

JEDEC expects the first generation of HBM3 products to appear on the market soon but notes that they won't meet the maximum specification. A more realistic outlook, it says, would be 2 GB modules in 12-layer stacks.

Image credit: Stephen Shankland