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Xilinx unveils a new class of compute IC 

Programmable device company Xilinx has outlined an architecture that it claims represents a new class of computing chip.

The silicon architecture has been four years in the making, involved 1,500 engineers and cost over $1 billion in R&D investment.

ACAP's functional blocks. Source: Xilinx

Dubbed the adaptive compute acceleration platform (ACAP), the first device will be fabricated using TSMC’s state-of-the-art 7nm CMOS process and will tape out later this year. The largest ACAP devices will use as many as 50 billion transistors.

“Based on the limited information from Xilinx, it is difficult to say what ACAP is, much less whether it creates a new product category,” says Linley Gwennap, principal analyst at The Linley Group.

That said, Gwennap believes the next-generation Xilinx products are far more than simply moving its FPGA technology to a 7nm CMOS. “The company has clearly put significant effort into improving the capabilities of these products to address 5G wireless, machine learning (AI), and other advanced applications,” says Gwennap.


The largest ACAP devices will use as many as 50 billion transistors



Xilinx says the relentless growth in data coupled with the emergence of artificial intelligence (AI) is driving new computing requirements. At the same time, Moore’s law is slowing down while the speed of innovation is outpacing silicon development cycles.

Victor Peng, Xilinx’s CEO, stresses that while AI is still in its infancy, the technology will be adopted across multiple industries. Thousands of applications will integrate some form of intelligence and this will occur at the network edge and in the cloud. “You will see AI end-to-end,” says Peng.  


Victor Peng

In this new era, chip architectures will be heterogeneous and use processing accelerators. “If you are going to have an intelligent, connected world, it really needs to be adaptable,” says Peng. “It needs to be adaptable because you cannot predict all the needs of the future.”

Gwennap says many companies have already delivered heterogenous chips, given the term heterogeneous refers to a mix of CPU, graphics processor unit (GPU) and digital signal processor (DSP) cores. “This includes every smartphone and PC processor shipping today,” he says.

It also is not clear what ‘adaptive’ means, adds Gwennap: “But if you interpret it to mean FPGA, then both Xilinx and Altera (now Intel) have delivered chips mixing CPUs, DSPs, and FPGAs for years.”


It configures a processor to do a job then, pffft, it has gone



Xilinx is not yet detailing the ACAP architecture until the first devices are launched but it has listed the main architectural features.

“Overall, it can be programmed at the hardware level and it has enough architectural features that it can be programmed purely from a software perspective,” says Peng. This means that things can be changed not just at the software level but down at the hardware level, dynamically, while the device is running.

“It configures a processor to do a job then, pffft, it has gone,” says David Manners, the veteran chip journalist at Electronics Weekly who has been covering Xilinx since it was founded in the 1980s.

The ACAP architecture will include both application and real-time processors as well as programmable logic for digital signal processing (DSP) and a hierarchy of distributed memory. The chip will also feature a high-speed network-on-a-chip linking the functional blocks and arbitrating between them.

ACAP will support various generations of DDR memory and certain family devices will include high-bandwidth 3D stacked memory. There will also be device members that use RF analogue-to-digital and digital-to-analogue converters.

In turn, ACAP will have fast input-output circuitry with serial/deserialisers (SERDES) running at 33, 58 and even 112 gigabit-per-second (Gbps) rates. Xilinx demonstrated its latest 112Gbps serdes at the recent OFC show held in San Diego.

Certain ACAP devices will use a novel engine that is software and hardware programmable. Programming the engine at the software level will require some embedded expertise.

“We are always looking at how we can use our hardware programming expertise to get another level of optimisation beyond just software-programmable blocks,” says Peng. Xilinx will detail the engine’s workings later this year.

Xilinx says the 7nm ACAP will deliver a 20x AI compute performance improvement and 4x the 5G communications bandwidth compared to its current 16nm FPGAs.

The company has already delivered software tools for ACAP to select customers and expects first device shipments in 2019.


Data-centre focus

Peng, who has been CEO since January, says the data centre market is now Xilinx’s top priority segment.

Data centres require ever more computing while their networked architectures continue to evolve. This represents an attractive market for Xilinx especially given its programmable devices not only serve computing but also storage and networking requirements.

Xilinx has also been expanding its software development environments that let its devices be programmed at a higher level by developers that have little or no knowledge of the underlying hardware. This contrasts with traditional Xilinx FPGA users that by nature are hardware engineers. “There are easily 1000x more software developers than FPGA developers,” says Peng.

Companies such as Amazon, Alibaba, Huawei, Baidu, Nimbix and Tencent also offer FPGAs-as-a-service as part of their cloud offerings.

The central role of software in data centres may have caused chips to recede into the background, yet Xilinx will argue that the nature of the silicon has never been more important.      

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