Xref: utzoo comp.os.msdos.misc:375 comp.sys.ibm.pc.misc:2255 comp.windows.ms:5860
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!julius.cs.uiuc.edu!apple!vsi1!hsv3!jls
From: jls@hsv3.UUCP (James Seidman)
Newsgroups: comp.os.msdos.misc,comp.sys.ibm.pc.misc,comp.windows.ms
Subject: Re: NEC 3D OK in interlaced 1024 x 768 ??
Message-ID: <5099@hsv3.UUCP>
Date: 2 Oct 90 23:06:35 GMT
References: <1618@mitisft.Convergent.COM> <1990Sep28.235629.15785@rick.cs.ubc.ca> <5061@hsv3.UUCP> <1990Oct2.152122.25078@ee.rochester.edu>
Reply-To: jls@headland.UUCP (James Seidman)
Organization: Video Seven / Headland Technology
Lines: 29

In article <1990Oct2.152122.25078@ee.rochester.edu> stanojev@ee.rochester.edu (Bob Stanojevich) writes:
>I am not sure but it seems to me that there is no point to have non-interlaced
>monitor if the pixel clock frequency is smaller them 90Mhz since the
>refresh rate will be below 50Hz-55Hz what is considered minimum for any
>reasonable flicker free non-interlaced display. Many of high end displays
>have 66 - 70 Hz refresh rate and that requires pixel clock of 120 - 150 Mhz
>for megapixel display.

You certainly don't need clocks that high!  As a rough order of magnitude
for clock speeds, you can use this formula:

(horiz. resolution) * (vert. resolution) * (frame rate) * 1.33 = (pixel clock)

In any case, there's a big advantage to having a 60 Hz non-interlaced display
over an interlaced one at 88 Hz.  And this 60 Hz 1024x768 display can be
done at a mere 65 MHz pixel clock.

>So far almost all SVGA boards have clocks in the
>range of 40-50 Mhz. I can not see how they can achieve better refresh rate
>then 45-50Hz in non-interlaced mode with that clock speed..

I'll strongly disagree with this one.  Names that I can come up with off
my head which have greater than 50 MHz clocks on their SVGA boards are
Video-7, Orchid, Everex, Sigma, WDI, and ATI.  (Many manufacturers are
missing here, as I said these are off the top of my head.)-- 
Jim Seidman (Drax), the accidental engineer.
"There's a certain freedom to being completely screwed." - The Freshman
UUCP: ames!vsi1!headland!jls
ARPA: jls%headland.UUCP@ames.nasa.arc.gov