On 5/24/05, Jack Carroll <[EMAIL PROTECTED]> wrote: > Thinking about internal vs. external DACs... I find it hard to > believe that a set of DACs resident on a chip full of logic can operate as > cleanly as an external DAC. For one thing, the lead frame inductance is > pretty much guaranteed to cause pseudo-random bouncing as the various gates > and registers shove charge around. For another thing, a process optimized > for logic probably isn't going to deliver the most accurate and > fastest-settling analog switches, or the lowest-capacitance circuit nodes. > Good analog processes tend to run at higher voltages than the latest and > fastest CMOS can survive, I think. So I tend to think some users will > happily pay for state-of-the-art off-chip video DACs, and others won't. > Maybe when it comes time to design the second-generation boards > implemented with ASICs, the DACs might be placed outboard to eliminate cable > effects. A DVI-to-analog external accessory might even become a product in > its own right, usable with anybody's fast graphics board. > There might even be a board family down the road, with a larger > outline than the regular one, that carries both the ASIC and one or two > FPGAs to extend the logic itself. That, too, could extend the production > life of the first ASIC.
According to our senior ASIC designer, electrically isolating a DAC inside of the ASIC is not a problem. Apparently, the power can be decoupled, and there are opportunities to add external caps to keep the power rail smooth. I agree that there could be greater cross-talk, but I'm getting the impression that this will make the difference between 300MHz and 350MHz, but I'm just guessing. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
