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Technology Stocks : Rambus (RMBS) - Eagle or Penguin -- Ignore unavailable to you. Want to Upgrade?

To: John Walliker who wrote (33581)	11/2/1999 6:53:00 AM
From: Bilow	Read Replies (1) \| Respond to of 93625

Hi John Walliker; You are using 0.8V / 28 ohms = 29mA as the output current of devices driving the Rambus channel. If you look in the data sheet for RDRAM, you will notice that the outputs are specified for 30mA to 90mA. The typical worst case output current is 60mA. The "typical" is for a standard impedance bus. The worst worst case output current, from the RDRAM specs, is 90mA. Engineers generally design for worst case specifications, and I believe that the Intel engineers are no different than other engineers in this. So I used about 90mA for my calculations. This is why my numbers are about 3x yours. The incoming data bus width is 18 signals wide, but there are also some clocks to take care of. Anyway, try redoing some of the calculations with these comments in mind. -- Carl P.S. One of the reasons for the higher than expected pin count in the RDRAM interface could be that the repeater hubs also include drive circuits for the various clocks that are required... You would think that the clock driver chip would have to be near the end of the Rambus channel, and so would be on a different chip, but it could be that they decided to route it out of the controller chip in order to reduce parts count (and cost). This would be rather inadvisable, I would think. I should call up Intel and get a copy of their interim data sheet for the part and quit making these guesses... But that would seem too much like work. Why don't you call them up and figure out what is happening with the pin counts of the 82803 and 82804?