Video Memory Bus - Hasta la vista, buses...

One of the most unaddressed topics for mobility products has been memory bus termination. Buses are routed on high speed PCB traces that work in the similar sense to transmission lines. If you leave the "lines" open, electrical signals could reflect back and distortion with the communication of the controller and controlled devices. Signal distortion can produce or contribute to things like erroneous bits in data, false memory addresses, etc. The way to avoid this is to use termination to close each end of the buses with resistor circuits.

As far as we know, there are no mobile GPU designs that use full termination (also called parallel termination). Serial and no termination have been the traditional methods used for virtually all notebook designs. Note that ATI's own brand of desktop cards implement full termination. This is in the sense of the GPU memory bus not the AGP bus, which are independent of one another.

This is what Rahul Sood, President of Voodoo PC, had to say on the topic:
There are traditionally three memory termination options depending on trade-offs amongst performance, power consumption and PCB space. They are: no termination (lowest speed, least PCB space requirement), serial, and full termination (highest speed, largest PCB space requirement).

For short traces (< 2 inches), the so called "half parallel" termination, essentially full termination without the series resistor, is a good compromise between performance and space requirement.
The implementation of full termination comes with several trade offs, like increased power consumption/thermal emissions and an increase in necessary PCB real estate, while the system generally benefits from performance and the ability to crack up the clocks. We have been told that there may be a fully terminated Mobility Radeon 9700 design popping up sometime soon, but the details are still sketchy at this point.
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  • Platter - Saturday, February 14, 2004 - link

    Suppose, just for the sake of argument, that the recent official announcement from IBM regarding the 970FX has something to do with ATI's 'Big One™'?

    PowerBook G5, anyone?
  • Andrew Ku - Monday, February 9, 2004 - link

    Ok, so to answer some of the inquires posed to me - if you currently own a Mobility Radeon 9600 (one of the three) based notebook, you are more or less set to go. The Mobility Radeon 9700 in the majority of cases behaves like an OC'ed version of its predecessor. However, the M10 is still a very hardy chip seems like it is going to have a long life cycle.

    As for waiting time, it looks like the bulk of the design wins won't start to be announced until the end of Feb. So go with a M10 based notebook if you plan to buy within the next few months or if you are just looking for the "traditional notebook." It's going to take some time before mainstream sees M11 in their mobile systems. And when it does, M11 will be in DTR notebooks for the most part.
  • Serp86 - Thursday, February 5, 2004 - link

    i think that the performance difference is quite enoght to justify calling it a 9700.
  • yomer - Thursday, February 5, 2004 - link

    So Andrew, Dell is supposed to be one of the bunch in adopting the M9700. Might Dell be called BIG? I wanted to buy an IBM t41p with a mobility firegl T2(based on the 9600) with 128MB. Should I wait and buy a notebook with the new M9700? Is it worth it? How much should we wait in oder to be able to buy one of thoes notebooks here in the US?
  • TrogdorJW - Wednesday, February 4, 2004 - link

    #9, it's all marketing. There will be enough people out there that don't know hardware who will just assume the 9700M is the same as the desktop 9700. Too bad for them. The important thing is that the M11 *is* quite a bit faster than the R9600 Mobility Pro, right? Or maybe they should have called the part the Mobility Radeon 9800 SE? ;)
  • CaptainSpectacular - Tuesday, February 3, 2004 - link

    ok ATI, what's with the naming scheme. this is absolutely awful! This part has nothing to do with the desktop 9700. I understand the dilema as presented, but what's wrong with 9650? or some other similar variation? the name 9700 is flat out misleading, regardless of how you justify it. This is almost as bad as nvidia calling the NV17 a GeForce4 series card (ok, not nearly that bad, but same idea...)
  • Slappi - Tuesday, February 3, 2004 - link

    Well if it is BIG I would think the biggest notebook maker is Toshiba and they are all Nvidia now so....... that would be huge.

    Do I get a cookie?
  • Andrew Ku - Tuesday, February 3, 2004 - link

    #6 - Sorry, no hints. You can count all the big guys on a single hand, and so there isn't much point in the old'e guess and check.
  • yomer - Tuesday, February 3, 2004 - link

    Andrew please! Tell me that the big name is not IBM!!
  • Andrew Ku - Tuesday, February 3, 2004 - link

    #2 - From our talks with the OEMs and ODMs, we understand that the pricing between the two chips is basically pocket change for prospective notebooks owners.

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