Derivative ICs: A Look At The Options

By Ann Steffora Mutschler
With the cost of designing and producing even moderately advanced SoCs skyrocketing, semiconductor companies and systems houses must find ways to defray the cost across a larger number of end uses than ever. As such many companies have adopted a platform-based derivative design approach, with that the platform serving as the first SoC design of a new family.

That strategy is expected to become far more widespread as mainstream process nodes push beyond 40nm, outsourcing of entire subsystems becomes more popular, and stacking of die gains traction.

“There used to be this idea that you would define this platform and all the chips would be derivatives of that platform,” said Drew Wingard, CTO at Sonics. “Now it’s more of, ‘No, we can’t afford to think about trying to build the platform itself. Instead, we are going to build the first chip, but we are going to use a platform-based design approach, which basically says we’re going to set ourselves up so that we can make derivatives.’ The way to sell this to more people is to personalize it for different customers or for different markets or for different regions of the world by making these derivatives. I think that’s a very common need that’s expressed to us by our customers, and it’s all of course about defraying the cost.”

But what exactly is a platform? A commonly cited definition was provided by Alberto Sangiovanni-Vincentelli, a professor of electrical engineering at the University of California at Berkeley, who is best known for co-founding both Synopsys and Cadence. He defined a platform as a set of choices that you’ve made, and because you’ve made those choices you can then abstract upwards from them to a higher level of design abstraction. And because you’ve fixed those aspects, you can refine downward.

“So the question then in a platform design is, ‘What things do you fix, what decisions do make and what decisions do you make flexible,’” said Wingard. “What things can you make different in each of the different derivatives? That’s what gets interesting about this whole theory of platform-based design.”

Of course, companies like Intel have been derivative powerhouses from the very beginning, noted Naveed Sherwani, president and CEO of Open-Silicon. “That’s actually what their strength is. They would have one or two teams chase new designs, then they would have 5, 10, or 15 teams do derivatives. The challenge is not actually to do derivative engineering. The challenge is how to do derivative engineering in the most cost-effective fashion.”

What is considered cost-effective today, however, is a different formula from what applied five years ago.

“Derivatives are being used to chase smaller and smaller markets because markets are fragmenting,” Sherwani said. “We have the long tail effect. We don’t have that $3 billion market to chase. Those are few and far between. Now we have to go chase that $200 million or $400 million market. Previously you could be more inefficient in your derivative design and you could afford to be late, but now you have to be very efficient because you are chasing a smaller market.”

A second consideration is to determine if a derivative will be outsourced. That requires effort in every aspect of chip development. “You have to have a full vertical team, and that’s not quite the case when we’re doing ASICs. Somebody is giving us fully functional RTL and our job is to do physical design, tape it out and get a working part. That is a completely different phenomenon when you go to derivative design,” Sherwani continued.

Closely connected with this decision is the rapid rise in various forms of die stacking—system in package or 2.5D with a silicon interposer—which has given semiconductor and systems developers a greater degree of freedom to choose the right option for their situation.

In this realm, Jack Harding, president and CEO of eSilicon explained the company is seeing large semiconductor and systems companies who say, “I’ve got this large inventory of successful parts. I’ve got for example, 180nm die sitting on the shelf and I’ve got this other 65nm die I got from the guy down the street and I got this RF radio I got from Skyworks and I’m going to put that all together and make some sort of product as opposed to actually making a brand new chip. The thought process is much like making a derivative. You’re making an architecture, you’re considering the software implications, you want to use as much of each, but you’re approaching it from two radically different perspectives.”

One involves making a chip that is a superset of something a company has already created. A second involves piecing it together with components the company can acquire. “Or we can try to piece it together with stuff that you have or you think you can get,” Harding said. “Let’s make a chip that is packaged or a device is good enough and get that to your customers in six months instead of three years and the NRE is $100,000 instead of $6 million. If it really takes off, then we’ll go and make the ASIC and we’ll make that single, advanced node part. If you think about the need to have a derivative, there are really two vectors to go down. One is the die-level, advanced-packaging approach. The second is to simply modify the RTL and re-tape out a version of the chip which is kind of ‘close enough.’”

A third option, of course, is to never make a chip and simply go to an FPGA.

Outsourcing grows, but not because of cost
No matter which approach is used, outsourced teams play larger roles than in the past. “A lot of global companies have that mantra of you build one design in one location and then you ship it somewhere else for derivatives,” said Michal Siwinski, group director of product marketing in the system and software realization group at Cadence. “I’m seeing at least in the leading companies something a little bit different. The geo teams are not just being treated as a cost reduction. Rather, due to the sheer complexity of what it takes to build these massive SoC platforms, you basically have these globalized teams that might take a lead on a specific derivative.”

In general, the big savings that made headlines a decade agp by outsourcing to lower-cost labor areas are no longer an option.

“Due to the complexity of re-integration, I’m not seeing that so much now,” Siwinski said. “A whole product line with its derivatives might be led by one geography versus the other, but in general the complexity of doing that derivative and the time and cost are at this point so prohibitive on their own. If you consider that a new design is $150 million, and the derivative might be $100 million, that’s still not cheap. So it’s not about notions of having lower cost to the derivatives. Rather it’s utilizing a global workforce where a lot of that expertise needs to be built in all the geographies.”

Architectural decisions drive derivatives
With all of this complexity, there is a lot more up-front work required to define what the platform is and what new market segments it can serve, in addition to the main business unit’s market. “There’s more coordination within the corporation and more cooks in the kitchen up front,” said Kurt Shuler, vice president of marketing at Arteris. “That takes a long time and there’s a lot of coordination of the different groups, because what happens is when that platform goes from one business unit to another business unit, the IP that that second business unit uses may be totally different than what the guys who created the platform for.”

Jon McDonald, a technical marketer at Mentor Graphics noted, “When you think about outsourcing, it all comes back to understanding what needs to be done. The traditional approach when people just started RTL design was that it was easy when a group is all in one location. If you have a design group and they’re all together, they have meetings daily or weekly. Everybody is talking and you communicate a lot of things informally. When you go to outsource something you’ve got to have a contract. And it’s not just a business contract. There’s got to be a development contract. If that development contract is not very specific and very rigorous, there are opportunities for miscommunication, there are opportunities for something to be delivered that doesn’t satisfy the need.”

To combat this, in many situations the delivery contract is an executable transaction level model, which is completely unambiguous and allows each party to say, “This is what I need: this is the performance I need. You need to deliver a subsystem or part or whatever it is that does exactly what this does with this performance and this architecture,” he continued. “By putting a little bit more into the upfront specification/the upfront architecture, if you have an executable model for the upfront architecture and a prime [mil/aero contractor] hands that to a subcontractor, it makes the process so much easier because they know what it needs to do.”