Berkshire-based Sondrel has tape-out of its largest chip design for a customer – with a 500mm2 footprint, over 30 billion transistors, 40 million flip-flops, and 23 thousand pads for I/O, power and ground.

Sonderel-tape-out

Up to 200 engineers were working on it simultaneously at times, according to the company.

“This initially started out as a design for 28nm technology,” said Sondrel director of physical design Stuart Vernon. “However, it soon became apparent that on 28nm it would either be one very big chip, which would not have been cost effective, or it would have to be be split into two connected chips, which would introduce parasitics and timing issues. So the decision was made to use the 16nm TSMC process node.”

Around a third of the floor plan is a customer IP block that handles real-time image processing.

Around that Sondrel wrapped a GPU, two CPUs, on-chip cache, PCI interfacing, USB interfacing and memory controllers for off-chip memory “using over 7km of metal tracks on a chip the size of a postage stamp”, said the company.

“It would be impossible to design a chip of this complexity in one go as it has 300 million placeable logic cells and the placement tool can only handle three million at a time without the run-time becoming excessive,” said Sonderel. “It was therefore divided into manageable-sized, functional blocks over four levels of a hierarchy structured like a pyramid. This enabled the design of the blocks to be divided between Sondrel teams that are located around the world. Once each block was finished, the big challenge was to bring them all together by creating abstract models of the lower blocks to provide input for the higher blocks so that the size of the part of design being implemented remained manageable. As the chip can run at up to 100W, even the heat output of the different parts of the chip have to be allowed for in the design to prevent hotspots.”

Once implemented, the whole design was run as one on a farm of 25 computers, each with 24 CPUs and 1.5Tbyte of memory. Physical validation checks took two days, and required over 100 software licenses.

“We are one of the few digital design companies that can handle a design of this size and complexity, and we have several more nearing completion,” said Sonderel CEO and founder Graham Curran. “A key part of this is our experience of managing the logistics of having teams in seven different locations and co-ordinating their work. For example, our teams in India and China work in the evenings to maximise the overlap with our teams in Europe.”

Sondrel was founded in 2002, and is based in Reading with offices in China, India, France, Morocco and North America.