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Technology Stocks : Rambus (RMBS) - Eagle or Penguin
RMBS 92.37-0.4%3:59 PM EST
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To: Bilow who wrote (50106)8/18/2000 7:44:57 AM
From: John Walliker  Read Replies (1) of 93625
 
Carl,

He said it was a serial interface that ran at 10Mbits/sec, and consisted of four wires: A differential clock, and differential data. The peak transition rate on each wire was 10 million per second, both clock and data, just as in DDR. He said that because of the differential drive and the balanced peak bandwidth between clock and data, it could drive quite long lines. In his lab, he got it to run long enough to hold ten bits in the wire simultaneously.

Do you know how he overcame frequency dependent dispersion? Your numbers imply a cable length of about 200m. I worked on a digital television distribution system in 1974 which operated at a clock frequency of around 13MHz (3 x colour subcarrier) without double clocking. The transmission velocity of long strings of the same state was different from that of rapidly alternating bits. This meant that for some data patterns the relative timing between clock and data became too large, even with regenerators at 50m intervals. I would therefore be very surprised if the system you described could have worked reliably without data scrambling before transmission to overcome this problem. It was to overcome such problems that the Manchester coding used in Ethernet was invented.

John
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