AMD Radeon VEGA gpu All About Memory
Channel: BE KYPO
Date: 2017-05-09

All about memory

When it comes to onboard memory, Vega is downright revolutionary—just like its predecessor.

AMD’s current high-end graphics cards, the Radeon Fury series, brought cutting-edge high-bandwidth memory to the world. Vega carries on the torch with improved next-gen HBM2, bolstered by a new “high-bandwidth cache controller” introduced by AMD.

Technical limitations limited the first generation of HBM to a mere 4GB of capacity, which in turn limited the Fury series to 4GB of onboard RAM. Thankfully, HBM’s raw speed hid that flaw in the vast majority of games, but now HBM2 tosses those shackles by the wayside. AMD hasn’t officially confirmed Vega’s capacity, but the overlay during the Doom demo revealed that particular graphics card packed 8GB of RAM. And that super-fast RAM is getting even faster, with AMD’s Joe Macri stating that HBM2 offers twice the bandwidth per pin of HBM1.
But as it turns out, HBM was just the beginning. “It’s an evolutionary technology we can take through time, make it bigger, faster, make all these key improvements,” said Macri, a driving force behind HBM’s creation. Vega builds on HBM’s shoulders with the introduction of a new high-bandwidth cache and high-bandwidth cache controller, which combine to form what Radeon boss Raja Koduri calls “the world’s most scalable GPU memory architecture.”

AMD crafted Vega’s high-bandwidth memory architecture to help propel memory design forward in a world where sheer graphics performance keeps improving by leaps and bounds, but memory capacities and capabilities have remained relatively static. The HB cache replaces the graphics card’s traditional frame buffer, while the HB cache controller provides fine-grained control over data and supports a whopping 512 terabytes—not gigabytes, terabytes—of virtual address space. Vega's HBM design can expand graphics memory beyond onboard RAM to a more heterogeneous memory system capable of managing several memory sources at once.
That’s likely to make its biggest impact in professional applications, such as the new Radeon Instinct lineup or the cutting-edge Radeon Pro SSG card that graft high-capacity NAND memory directly to its graphics processor. “This will allow us to connect terabytes of memory to the GPU,” David Watters, AMD’s head of Industry Alliances, told PCWorld when the Radeon Pro SSG was revealed, and this new cache and controller architecture designed for HBM’s blazing-fast speeds should supercharge those capabilities even more.

To drive the potential benefits home, AMD revealed a photorealistic recreation of Macri’s home living room. The 600GB scene normally takes hours to render, but the combination of Vega’s prowess and the new HBM2 architecture pumps it out in mere minutes. AMD even allowed journalists to move the camera around the room in real-time, albeit somewhat sluggishly. It was an eye-opening demo.
Koduri stressed that games can also benefit from the high-bandwidth cache controller's fine-grained, dynamic data management, citing Witcher 3 and Fallout 4, each of which actually use less than half of the memory allocated by the games when they’re running at 4K resolution. “And those are well-optimized games!” he said. Memory demands are only getting greedier in high-profile games, and doubly so at bleeding-edge resolutions. Here’s hoping that the HB cache’s finer controls paired with HBM’s sheer speed—and other tweaks we’ll discuss later in this article—alleviates that somewhat.

AMD also says that future generations of games could take advantage of high-bandwidth memory design to upload large data sets directly to the graphics processor, rather than handling it with a more hands-on approach as done today.