Will the Real Enchilada Please Stand Up?

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Will the Real Enchilada Please Stand Up?

By Peggy Aycinena
Posted 02/26/01, 07:29:16 PM EDT

On the theory that it's better to ask a stupid question than to make a stupid mistake, I often find myself asking company spokesmen: "What's an SOC?" The answer given in quick reply, usually with a bit of a pedantic chuckle: "An SOC is a system on a chip."

"Yeah, okay. So what's a system on a chip?" The answer to that question never comes as quickly and rarely with a chuckle-pedantic or otherwise. In fact, the answer is usually preceded by a sigh. Why?

Because, most technologists must deal with the same transient semantics in electronics that we all wrestle with. It's a whole lot easier to use a catch-all phrase like system on a chip, and let the meaning be implied, than to articulate the exact definition of such a phrase.

So, after the requisite sigh, what kinds of definitions are in use today for an SOC? Well, let's start with David Shanahan's column in this month's issue: "Today's SOC designs typically contain micro-controllers, digital signal processors, memories, peripherals, and physical-interface connections to external devices all in a single package." That's pretty straightforward, so why look any farther? Well, there are lot of folks out there using definitions other than David's that are neither as clear-cut nor as confident.

Here's a sampling of responses to the deceptively easy question: "What's an SOC?"

"First off, it depends on who you're talking to, because depending on the end-use, an SOC can mean so many different things."

"It's a combination of analog and digital on a chip-and a large chip at that."

"An SOC is a product that ends up in a cell phone and probably has DACs, and so forth."

"If you can just drop it into your design, it's an SOC."

"I can't define a system on a chip."

"If you've got a microprocessor, memory, software, controllers, digital hardware, and analog functions all integrated on a single piece of silicon, you've truly got a system on a chip."

"It's a successful chip that can be used in production."

"It's a chip that's designed with an end-system in mind."

"The world is analog. If you've got a chip that can interface with signals from an analog world and compute an output on a digital single-chip platform, you've got a system on a chip."

"If you've got everything that was once on the board now rolled up on the chip, you've got an SOC."

"If it's got over 100,000 gates, it's probably a system on a chip."

"It's a big chip."

"In its simplest sense, it's the integration of a microprocessor-or multiple microprocessors-and some memory, controllers, and interface to the board"

"If all kinds of stuff that was once on the board is now on the chip, that's an SOC."

"The definition's not important. It's only important that I-as an ASIC designer-think now in terms of designing systems and not just in terms of designing ASICs."

"Every chip that has a microprocessor in it is a system on a chip."

"It's a generic, knobbly thing."

And so the definitions go-adding confusion, not clarity, to a technology and a term that glibly describes and inefficiently defines the most promising wave in the future of design. Not surprisingly, I continued to be frustrated with the list of responses I had gleaned from industry until I recently met a feisty ASIC designer long on confidence and short on patience.

"So, what's an SOC?" I asked him.

He didn't hesitate for a moment. "An SOC," he said with a flourish, "is the whole enchilada!"

Excellent. I couldn't have put it better myself.

Okay. One down, three to go.

First: "What's an embedded system?" Second: "What's an HDL?" Third, and most important to recent polls in EDA: "What's a tape-out?"

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