Why DDR?

Hello everyone, I wonder if someone could explain me what's all the fuss around DDR. If you're driving data at double clock rate, why not feeding the chip with double clock (or DQS) rate in the first place? What do we gain from all the dual edge strobing mess?

Thanks, Avishay

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Idunno, but it's really big in Japan.


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Tim Williams

The data rate is what is the most important factor. The faster the better (or so we're told).

With single data rate, the maximum frequency content is always contained in the clock so it's the toughest signal to transmit. With double data rate, the frequency content of the clock now never exceeds that of the data.

Don't get too excited about whether it's SDR, DDR, FDR, or BFD. The data rate is the thing that drives the technology. The clock rate is only there for support.


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Die DDR wurde in 1949 proklamiert. Die Kommunisten steuerten es. Seit Oktober 1989 ist est mit der Bundesrepublik Deutschland vereinigte.

Reply to
Paul Burke

You save a factor of 2 on the frequency of the clock signal. Since that's the fastest signal involved, the factor of 2 is important.

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Reply to
Hal Murray

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