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

To: Tenchusatsu who wrote (31385)	10/1/1999 9:26:00 PM
From: Brian1970	Respond to of 93625

Dang! 294 posts since Wednesday!! You guys tire me out (and that's not easy)...

To: Tenchusatsu who wrote (31385)	10/1/1999 10:16:00 PM
From: Bilow	Read Replies (4) \| Respond to of 93625

Hi Tenchusatsu; Re those layer counts... The only reason I have ever heard for someone going from four layers to six, is to improve routing, usually because of a high trace count. Increasing the number of layers causes the traces to be farther apart from one another on any give layer, for instance. My guess is that they are getting noise reception from non Rambus traces onto the Rambus channel. Those long lines act like radio antennas, so they have to be real careful. On the one hand, the Rambus channel is deliberately designed to use fewer traces, so you would think that they could get away with fewer layers. But on the other hand, the spaces and traces on Rambus are larger. Trace width is larger in order to reduce impedance, (I believe). Space width is larger to reduce cross talk. So I would guess that they have some less than optimal signal connections near the Rambus channel, and going to six layers will allow them to get the noisy non-RDRAM signals away from the RDRAM layer a little quicker, maybe even completely separated by a ground plane. Of course INTC will announce new specs for motherboard design. I bet they will require wider spacing between Rambus wires, and other Rambus wires, or other system wires. One of the worst experiences for a design is having to pass FCC requirements, by the way. There is a big test at an FCC testing site, (frequently owned by the corporation), where emissions are tested for the system. The FCC engineers ask for changes to the circuitry, not all of it in the direction of improving signal integrity. (G) But I wouldn't think that the FCC guys would be allowed near the Rambus termination, it is just too optimized to trick around with. I would have thought that Rambus would have problems with FCC, but none of the reports indicate this. I really don't know. Should be interesting, though. Incidentally, it seems that you never see boards with an odd number of layers (except single layer boards). I believe that this is because the equipment always does two sides at a time... I think that it is really weird that INTC hasn't announced more about the cause of the problem. Maybe they are giving suggestions to their big customers, but it seems like they might get more little houses to consider putting out an RDRAM design (for embedded applications, for instance,) if they give a few hints as to what they think needs to be changed. Maybe they have a formal bug reporting and fix verification sequence that they have to go through. But I think it would be better if they shot just a little from the hip right now. I am sure that there is a guy somewhere in Intel that knows what the problem is, and knows how to fix it right now. But it is a big company, and it takes a while to make decisions. -- Carl