Source: Content compiled from tomshardware

The GDDR7 SGRAM specification supports data transfer rates up to 48 GT/s, but first-generation GDDR7 memory devices can operate at up to 32 GT/s. But it looks like GDDR7 will soon move on, as at the upcoming International Solid-State Circuits Conference (ISSCC), both Samsung and SK Hynix plan to discuss their GDDR7 solutions with a data transfer rate of 42 GT/s, according to advance planning for the event.

Plans of Samsung

Samsung plans to describe its 24Gb (3GB) GDDR7 memory device, which has various enhancements to support data transfer rates of up to 42.5 GT/s, which translates to a peak bandwidth of up to 170 GB/s. The device will offer tangible improvements in capacity and performance compared to existing GDDR7 products. Currently, the company produces 16Gb (2GB) GDDR7 memory chips that can run at speeds of up to 32 GT/s, providing a peak memory bandwidth of 128 GB/s.

In practical applications, a 24Gb GDDR7 memory chip with a 42.5 GT/s data transfer rate could enable graphics card manufacturers to build graphics cards with 48GB of memory and up to 2.7 TB/s peak bandwidth on a 512-bit interface.

To enable its upcoming 24Gb GDDR7 SGRAM devices to achieve such high data transfer rates with predictable power consumption and reliability, Samsung had to implement multiple features such as low-power write clock (WCK) distribution for improved energy efficiency, resistor/capacitor optimized dual-stress transmitters for high signal integrity, and advanced voltage and timing margining enhancements to maximize performance reliability and stability under high loads.

SK Hynix

Unlike Samsung, which has described its 24Gb GDDR7 chips in detail, SK Hynix plans to focus on its 42 GT/s single-ended PAM-3 receiver for the GDDR7 memory interface. The key feature of this receiver is its single-ended hybrid decision feedback equalization (DFE), which ensures that the signal transmitted over the memory interface maintains its integrity even in the presence of high noise levels, crosstalk, and inter-symbol interference (ISI) that are expected at 42 GT/s.

This single-ended hybrid DFE is actually a key feature required to reliably achieve high data transfer rates, so let's discuss it in more detail.

Feedforward equalizers (FFE) often help reduce signal distortion caused by intersymbol interference, which occurs when a previously transmitted symbol interferes with the current symbol. While FFE is effective for linear ISI (caused by frequency-dependent losses), it is less effective for nonlinear ISI (caused by reflections, noise, or crosstalk). Nonlinear ISI often requires additional techniques, such as DFE. Decision feedback equalizers (DFE) use feedback from previously decoded bits (decisions) to cancel interference from previously decoded signals.

View more at EASELINK