Re: xserver-xfree86 and GeForce 2 MX 400
On Tue, 5 Nov 2002 18:31:20 +1100, Rob Weir <rweir@softhome.net>
wrote:
>On Mon, Nov 04, 2002 at 06:01:49PM -0500, Dale Scheetz wrote:
>> The problem is, all I've found so far on the web is info suggesting that
>> the "natural" resolution for this card is 2048 x 1536 @ 75 Hz. What I need
>> is a way to translate this information into refresh rates.
>
>I don't really know what the 'natural' resolution for a video card is.
>True, your card can probably handle that res, but it can also handle an
>order of magnitude below that.
>
From README.cirrus out of XF86 4.2:
>On older chips, the use of a higher dot clock frequencies has a negative
>effect on the performance of graphics operations, especially BitBlt, when
>little video memory bandwidth is left for drawing (the amount is displayed
>during start-up for 542x/3x/46/6x chips). For the 542x/3x chips, with
>default MCLK setting (0x1c) and a 32-bit memory interface, performance with a
>65 MHz dot clock can be half of that with a dot clock of 25 MHz. So if you
>are short on memory bandwidth and experience blitting slowness, try using the
>lowest dot clock that is acceptable; for example, on a 14" or 15" screen
>800x600 with high refresh (50 MHz dot clock) is not so bad, with a large vir-
>tual screen.
I guess the "natural" resolution & speed is that which gives the
"best" compromise between refresh rate and drawing performance. It's
probably that which Windoze calls the "optimal" rate.
The docs on SVGATextMode are v. good at explaining how to calculate
refresh rates and stuff.
Pigeon
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