Semiconductor History | SK hynix Icheon, October 2013 — Memory Moves Onto the Processor's Own Slab of Silicon

The large grey rectangle in the photograph is a graphics processor. The four smaller dark rectangles flanking it are memory, and the distance between them is a few millimetres. For thirty years memory had sat somewhere else. It went into sockets on a motherboard, connected by tracks measured in centimetres, and the width of that connection was the ceiling on how fast a processor could be fed. High Bandwidth Memory removed the distance. DRAM dies are stacked vertically, drilled through with copper vias, and mounted on the same silicon interposer as the processor, which allows a 1,024-bit interface instead of a few hundred. AMD had been working the problem since the middle of the 2000s and needed a memory maker willing to build something no customer had ordered. It went to SK hynix, and the two companies took the design to the JEDEC standards body from around 2010. JEDEC published the result as JESD235 in October 2013. The dating of the first working part is not as clean as the standard's. Most accounts credit SK hynix with producing the first HBM device in 2013; SK hynix's own newsroom dates the joint development with AMD to 2014. The company's telling and the outside record disagree by a year, and neither has corrected the other. What is firm is December 2013, when AMD's Bryan Black told a packaging conference that AMD was co-developing HBM with SK hynix and that stacks were already sampling. Volume production began at Icheon in 2015. The first product to carry it shipped that June: AMD's Radeon R9 Fury X, built on the Fiji processor shown here, with four HBM stacks giving four gigabytes and 512 gigabytes per second of bandwidth. It did not sell well. Four gigabytes was tight for a flagship graphics card in 2015, the stacks were expensive, and AMD later moved its flagship cards back to GDDR. The technology sat there, correct and unrewarded, until machine learning arrived with an appetite no motherboard trace could satisfy. Every generation since has been an allocation fight among three memory makers, and this campus built the first of them. The pin is Icheon because that is where the stacks are produced. The photograph is an AMD package rather than a plant, and it shows the geometry the whole argument is about. Photo: C. Spille / pcgameshardware.de, CC BY-SA 4.0, via Wikimedia Commons