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

To: grok who wrote (28840)	9/6/1999 11:27:00 PM
From: Dave B	Read Replies (1) \| Respond to of 93625

KZ, As I understand it, the traces go from the chip set to the first RIMM and then across the length of the first RIMM then over to the second RIMM and across it and then over to the 3rd RIMM and across it. That sounds like 8" or a little more. This was also discussed in the March/April discussion earlier this year. If you have the signal split off when it gets to the RIMM or DIMM (stubs I believe they're called) then you have to deal with reflections of the signals off the chips on the DIMM or RIMM. It really messes up the quality of the signal (the truly technical folks can explain it in more detail) and slows down the entire system (you have to wait for the reflections to settle). Current DIMM's split the signal (the trace goes up into the DIMM as well as to the next DIMM) and have this problem. RIMMs carry the signal up and across the RIMM so that the only stubs are the tiny little stubs to the individual pins of the chips (or maybe not even that -- I'm not sure). Dave

To: grok who wrote (28840)	9/7/1999 12:27:00 AM
From: Bilow	Read Replies (1) \| Respond to of 93625

Hi KZNerd; A note on those 8 inch busses... The maximum number of direct RDRAMs that you can put on one bus is eight. You will have to take my word that this maximum is related to the maximum length of the bus. Board designers will attempt to place those eight chips as close as possible. From this link, courtesy of Samsung: usa.samsungsemi.com The package dimensions for the edge bonded uBGA on page 61 of 64 is 7.7 x 12.7 mm. Eight across the short dimension would have a total width of 61.6mm or 2.5 inches. Spacing them out by a (sloppy) factor of two, would give a total distance of about five inches. Wire lengths should be held to around 6.5 inches. Adding the controller might take the wire length to 7 inches or so. While it might be possible to use longer busses, there isn't any reason or need to do so. -- Carl