On 3/17/06, James Richard Tyrer <[EMAIL PROTECTED]> wrote: > > The extra RAMDAC bits are used for gamma and color correction. You > still have only 8 bits per color in memory.
Understood. > The Philips 3xDAC has 10 bits per channel, and we are grounding the 2 > LSBs rather than connecting them to the FPGA. As I mentioned in another email, we simply haven't got the spare pins for it. If it becomes REALLY important, we can do temporal modulation. Tech Source and plenty of others have been doing it for ages with medical LCD displays at 60Hz. One of the design requirements is that OGA should be very good for 90% or more of desktop users. Very few are going to be overly concerned about gamma correction at all, let alone how many bits of precision on the DAC. I'm not, by any means, saying you don't have a valid point. But I am trying to determine how critical this is for most users and see how we could possibly solve the problem given the hardware constraints we have. There's another interesting point that you bring to light. The lower bits are grounded. If we can only afford the 8 bits from the FPGA, it would be technically better to connect the lower two bits to the same signals as the highest two bits. So I talked to Howard about it. He says that we can't even do that because those signal lines are already connected to two places, so we'd end up causing too much reflection. Besides, we can compensate for the tiny drop in peak voltage by adjusting resistors connected to the DAC. > > Isn't there only an amp for the highspeed DAC? Still, it's important > > that we get this right too. > > > Yes, I have now found the Philips TDA8777 which is about the same as the > Analog Devices one except for the sync and blanking. Do you think this one will do the job? _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
