Design007 Magazine

PCBD-Mar2015

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50 The PCB Design Magazine • March 2015 Guest Editor Kelly Dack stopped by the Cadence Design Systems booth at DesignCon 2015, where he sat down with Product Market- ing Manager Brad Griffin to discuss Cadence's advanced PCB design and signal integrity tools, and the company's focus on DDR. Kelly Dack: Brad, since you're the product marketing director for Cadence Design Systems, I'd like to ask a few questions about your DDR products. But first, please give us a brief over- view of DDR. Brad Griffin: I'd be happy to. One of the main points about a computer is that it has memory and you can store data in that mem- ory—that's kind of what makes it a computing device. So they've been finding ways over the life of electronics to store and retrieve data fast- er out of memory. Somewhere around 2002, we came up with this idea of doubling the data rate in DDR memory, or double data rate memory. Cadence's Brad Griffin Digs Deep Into DDR That was unique because basically, we clocked the data into the memory, both on the rising edge and on the falling edge of the clock. It was a clever way with the same sort of signaling to basically double the data rate speeds. KD: Was there an organization involved? Was it standardized? BG: That's really good question. As of right now, there's a standard committee called JEDEC, and I'm going to assume they were in place back in the 2002 timeframe, but I'd have to go back and check. But obviously there's memory companies and they have to be able to plug- and-play with different controllers as they're driving the memory, so there's probably always been a standard they've been marching toward. That process used to be a lot simpler. You'd be transferring data at maybe 100 megabits per sec - ond. You would send the data, clock it in, and it wasn't nearly as complicated as it is now. article

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