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Author Topic: 4850 and GTX 275 pixel clock  (Read 18095 times)
nnnta

Posts: 5


« on: October 24, 2009, 09:51:30 PM »

Hi,

I have both a 4850 and gtx 275.

My L227WTG 22" LCD can do 1680x1050 @ 75 hz with a 149Mhz pixel clock on the 4850 using powerstrip advanced timings but
with the gtx 275 the same resolution and refresh-rate gives in excess of 174Mhz pixel clock which the lcd starts to flicker.

Why does the gtx 275 give such high pixel clock and how do i reduce it to something like the 4850?

Also, i used to run 1680x1050@75hz on my 7900gt with no issues too.

thanks!
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Ashley Saldanha
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Posts: 1806


« Reply #1 on: October 25, 2009, 04:12:02 AM »

My L227WTG 22" LCD can do 1680x1050 @ 75 hz with a 149Mhz pixel clock on the 4850 using powerstrip advanced timings but
with the gtx 275 the same resolution and refresh-rate gives in excess of 174Mhz pixel clock which the lcd starts to flicker. Why does the gtx 275 give such high pixel clock and how do i reduce it to something like the 4850?

The only explanation is the other timing parameters are different. If you use the same timing string on both cards, the resulting pixel clock should be the same (or very near, +/- 1 MHz).


Quote
Also, i used to run 1680x1050@75hz on my 7900gt with no issues too.

Irrelevant - the 7900GT has nothing in common with the GTX275.
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nnnta

Posts: 5


« Reply #2 on: October 25, 2009, 01:14:22 PM »

i managed to get 75hz on the gtx 275 using the following.

PowerStrip timing parameters:
1680x1050=1680,48,32,80,1050,20,7,21,150660,512

Generic timing details for 1680x1050:
HFP=48 HSW=32 HBP=80 kHz=82 VFP=20 VSW=7 VBP=21 Hz=75

VESA detailed timing:
PClk=150.66 H.Active=1680 H.Blank=160 H.Offset=32 HSW=32 V.Active=1050 V.Blank=48 V.Offset=20 VSW=7

Linux modeline parameters:
"1680x1050" 150.660 1680 1728 1760 1840 1050 1070 1077 1098 +hsync +vsync

Where as the ATI 4850 gave me

PowerStrip timing parameters:
1680x1050=1680,48,32,80,1050,3,6,21,149143,532

Generic timing details for 1680x1050:
HFP=48 HSW=32 HBP=80 kHz=81 VFP=3 VSW=6 VBP=21 Hz=75

VESA detailed timing:
PClk=149.14 H.Active=1680 H.Blank=160 H.Offset=32 HSW=32 V.Active=1050 V.Blank=30 V.Offset=3 VSW=6

Linux modeline parameters:
"1680x1050" 149.143 1680 1728 1760 1840 1050 1053 1059 1080 +hsync -vsync
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Ashley Saldanha
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Posts: 1806


« Reply #3 on: October 25, 2009, 02:00:22 PM »

The difference is in the vertical sync width, resulting in a slightly different pixel clock.
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nnnta

Posts: 5


« Reply #4 on: October 25, 2009, 02:12:51 PM »

Is 1680x1050@75hz supposed to use around 150Mhz pixel clock?

Was wondering why my gtx 275 was giving me around 174Mhz.

I have to set the front porch to 20 to get 150MHz, but when i run a full screen program at the same resolution, it changes to a much higher pixel clock resulting in 1680x1050 on 840x1050 resolution
« Last Edit: October 25, 2009, 02:15:57 PM by nnnta » Logged
Ashley Saldanha
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Posts: 1806


« Reply #5 on: October 25, 2009, 03:02:54 PM »

Quote
Is 1680x1050@75hz supposed to use around 150Mhz pixel clock?

Supposed to? That's the wrong question. The question is "What timing does your monitor want?". A multisync CRT might want 188MHz, while a reduce blanking LCD might want 149MHz.

Run MonInfo on the LG and it will tell you exactly what LG recommends.
 
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nnnta

Posts: 5


« Reply #6 on: October 25, 2009, 09:55:33 PM »

Quote
Is 1680x1050@75hz supposed to use around 150Mhz pixel clock?

Supposed to? That's the wrong question. The question is "What timing does your monitor want?". A multisync CRT might want 188MHz, while a reduce blanking LCD might want 149MHz.

Run MonInfo on the LG and it will tell you exactly what LG recommends.
 


That means the graphics card outputs the pixel clock according to what the monitor wants? My L227WTG can accept 149MHz reduce blanking. It seems to work only if i don't switch graphics modes. When i run a full screen game for instance it will revert back to 188MHz, causing the resolution to become 840x1050

Quote
Monitor
  Model name............... L227W
  Manufacturer............. LGE
  Plug and Play ID......... GSM566F
  Serial number............ 236954
  Manufacture date......... 2008, ISO week 7
  -------------------------
  EDID revision............ 1.3
  Input signal type........ Digital
  Color bit depth.......... Undefined
  Display type............. RGB color
  Screen size.............. 490 x 320 mm (23.0 in)
  Power management......... Standby, Suspend, Active off/sleep
  Extension blocs.......... None
  -------------------------
  DDC/CI................... Supported
  MCCS revison............. 2.1
  Display technology....... TFT
  Controller............... Mstar 0x0
  Firmware revision........ 1.7
  Firmware flags........... 0x10068
  Active power on time..... 67 hours
  Current frequency........ 81.50kHz, 75.50Hz

Color characteristics
  Default color space...... Non-sRGB
  Display gamma............ 2.20
  Red chromaticity......... Rx 0.653 - Ry 0.341
  Green chromaticity....... Gx 0.231 - Gy 0.666
  Blue chromaticity........ Bx 0.150 - By 0.062
  White point (default).... Wx 0.313 - Wy 0.329
  Additional descriptors... None

Timing characteristics
  Horizontal scan range.... 30-83kHz
  Vertical scan range...... 56-75Hz
  Video bandwidth.......... 150MHz
  CVT standard............. Not supported
  GTF standard............. Not supported
  Additional descriptors... None
  Preferred timing......... Yes
  Native/preferred timing.. 1680x1050p at 60Hz (16:10)
    Modeline............... "1680x1050" 119.000 1680 1728 1760 1840 1050 1053 1059 1080 +hsync -vsync
  Detailed timing #1....... 1680x1050p at 60Hz (16:10)
    Modeline............... "1680x1050" 146.250 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync

Standard timings supported
     720 x  400p at  70Hz - IBM VGA
     640 x  480p at  60Hz - IBM VGA
     640 x  480p at  75Hz - VESA
     800 x  600p at  56Hz - VESA
     800 x  600p at  60Hz - VESA
     800 x  600p at  75Hz - VESA
     832 x  624p at  75Hz - Apple Mac II
    1024 x  768p at  60Hz - VESA
    1024 x  768p at  75Hz - VESA
    1280 x 1024p at  75Hz - VESA
    1152 x  870p at  75Hz - Apple Mac II
    1440 x  900p at  60Hz - VESA STD
    1280 x 1024p at  60Hz - VESA STD
    1280 x  960p at  60Hz - VESA STD
    1152 x  864p at  75Hz - VESA STD

Report information
  Date generated........... 10/26/2009
  Software revision........ 2.30.0.797
  Operating system......... 5.1.2600.2.Service Pack 3

Raw data
  00,FF,FF,FF,FF,FF,FF,00,1E,6D,6F,56,9A,9D,03,00,07,12,01,03,EA,31,20,78,EA,56,B5,A7,57,3B,AA,26,
  0F,50,54,A7,6B,80,95,00,81,80,81,40,71,4F,01,01,01,01,01,01,01,01,7C,2E,90,A0,60,1A,1E,40,30,20,
  36,00,DA,28,11,00,00,1A,21,39,90,30,62,1A,27,40,68,B0,36,00,DA,28,11,00,00,1C,00,00,00,FD,00,38,
  4B,1E,53,0F,00,0A,20,20,20,20,20,20,00,00,00,FC,00,4C,32,32,37,57,0A,20,20,20,20,20,20,20,00,7D



This is MonInfo's output.
« Last Edit: October 25, 2009, 09:58:26 PM by nnnta » Logged
Ashley Saldanha
Administrator
*****
Posts: 1806


« Reply #7 on: October 28, 2009, 01:29:01 PM »

So your LG wants 1680x1050 at 60Hz (not 75Hz), with a pixel clock of either 119MHz (with reduced blanking) or 146MHz (without normal blanking). It is *not* a multisync device.

If you really want to try to push RB up to 75Hz, you can try this timing:
1680x1050=1680,48,32,64,1050,3,5,12,146376,5

And Yes, of course the graphics card tries to output what the monitor wants - that's a Plug and Play requirement. And what your monitor wants is spelt out in detail in the MonInfo report.
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nnnta

Posts: 5


« Reply #8 on: October 29, 2009, 01:01:49 AM »

1680x1050=1680,48,32,64,1050,3,5,12,146376,5
 causes the lcd to "flicker"
1680x1050=1680,48,32,64,1050,3,5,20,146376,5
gets me a stable picture at 75hz

but when i change graphics mode like launching some games, the card outputs 1680x1050 but the display gives me 840x1050

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Ashley Saldanha
Administrator
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Posts: 1806


« Reply #9 on: October 29, 2009, 03:44:31 AM »

Quote
but when i change graphics mode like launching some games, the card outputs 1680x1050 but the display gives me 840x1050

I'm not sure what that means exactly. If the display is already at 1680x1050, why are you changing modes when launching games?

Close PowerStrip and post your pstrip.ini file. Then give me a step-by-step procedure to reproduce the problem.
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Rodpad

Posts: 4


« Reply #10 on: August 13, 2010, 06:38:54 AM »

I have the same problem. Worked fine on my 4850. Flickering on my GTX 275.

I presume it's the vertical back porch that needs to be manually increased, outside of the automatic calculations Powerstrip does in the advanced timing options.

Do I paste over the existing line on Powerstrip's ini file?

72hz in 1920x1080 is what I'm striving for and know my monitor can do (ala the 4850)
Powerstrip wants to do the following for 1920x1080 @ 72hz (flickering) on the 275. I don't have the 4850 timings to hand:
Quote
1920x1080=1920,88,44,148,1080,4,5,36,178200,512



My Moninfo details:
Quote
Monitor
  Model name............... G2420HDBL
  Manufacturer............. BenQ
  Plug and Play ID......... BNQ785F
  Serial number............ V2A08713SL000
  Manufacture date......... 2010, ISO week 8
  -------------------------
  EDID revision............ 1.3
  Input signal type........ Digital
  Color bit depth.......... Undefined
  Display type............. RGB color
  Screen size.............. 530 x 290 mm (23.8 in)
  Power management......... Active off/sleep
  Extension blocs.......... None
  -------------------------
  DDC/CI................... Not supported

Color characteristics
  Default color space...... sRGB
  Display gamma............ 2.20
  Red chromaticity......... Rx 0.649 - Ry 0.338
  Green chromaticity....... Gx 0.289 - Gy 0.609
  Blue chromaticity........ Bx 0.146 - By 0.070
  White point (default).... Wx 0.313 - Wy 0.329
  Additional descriptors... None

Timing characteristics
  Horizontal scan range.... 24-83kHz
  Vertical scan range...... 50-76Hz
  Video bandwidth.......... 170MHz
  CVT standard............. Not supported
  GTF standard............. Not supported
  Additional descriptors... None
  Preferred timing......... Yes
  Native/preferred timing.. 1920x1080p at 60Hz (16:9)
    Modeline............... "1920x1080" 148.500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync

Standard timings supported
     720 x  400p at  70Hz - IBM VGA
     640 x  480p at  60Hz - IBM VGA
     640 x  480p at  75Hz - VESA
     800 x  600p at  60Hz - VESA
     800 x  600p at  75Hz - VESA
     832 x  624p at  75Hz - Apple Mac II
    1024 x  768p at  60Hz - VESA
    1024 x  768p at  75Hz - VESA
    1280 x 1024p at  75Hz - VESA
    1152 x  870p at  75Hz - Apple Mac II
    1152 x  720p at  60Hz - VESA STD
    1280 x  720p at  60Hz - VESA STD
    1280 x  960p at  60Hz - VESA STD
    1280 x 1024p at  60Hz - VESA STD
    1600 x  900p at  60Hz - VESA STD
    1680 x 1050p at  60Hz - VESA STD
    1920 x 1080p at  60Hz - VESA STD

Report information
  Date generated........... 13/08/2010
  Software revision........ 2.52.0.857
  Data source.............. Real-time 0x0031
  Operating system......... 6.1.7600.2

Raw data
  00,FF,FF,FF,FF,FF,FF,00,09,D1,5F,78,45,54,00,00,08,14,01,03,80,35,1D,78,2E,60,85,A6,56,4A,9C,25,
  12,50,54,A5,6B,80,71,00,81,C0,81,40,81,80,A9,C0,B3,00,D1,C0,01,01,02,3A,80,18,71,38,2D,40,58,2C,
  45,00,DD,0C,11,00,00,1E,00,00,00,FF,00,56,32,41,30,38,37,31,33,53,4C,30,30,30,00,00,00,FD,00,32,
  4C,18,53,11,00,0A,20,20,20,20,20,20,00,00,00,FC,00,47,32,34,32,30,48,44,42,4C,0A,20,20,20,00,BA
« Last Edit: August 13, 2010, 07:13:39 AM by Rodpad » Logged
Ashley Saldanha
Administrator
*****
Posts: 1806


« Reply #11 on: August 14, 2010, 02:23:14 PM »

Try this:

PowerStrip timing parameters:
1920x1080=1920,88,44,148,1080,4,5,36,178200,1

Generic timing details for 1920x1080:
HFP=88 HSW=44 HBP=148 kHz=81 VFP=4 VSW=5 VBP=36 Hz=72

VESA detailed timing:
PClk=178200.00 H.Active=1920 H.Blank=280 H.Offset=72 HSW=44 V.Active=1080 V.Blank=45 V.Offset=4 VSW=5

Linux modeline parameters:
"1920x1080" 178.200 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
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Rodpad

Posts: 4


« Reply #12 on: August 14, 2010, 04:40:59 PM »

Thanks for the swift response.

Where do I input these options in the powerstrip.ini file?
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Ashley Saldanha
Administrator
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Posts: 1806


« Reply #13 on: August 15, 2010, 03:25:53 AM »

You don't.

1. Copy this string to the clipboard.

Code:
1920x1080=1920,88,44,148,1080,4,5,36,178200,1

2. PowerStrip menu > Display profiles > Configure
3. Switch to 1920x1080 if you aren't there already
4. Click Advaced timing options
5. Click the little paste-from-clipboard speed button (between Cancel and Apply)

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Rodpad

Posts: 4


« Reply #14 on: August 15, 2010, 03:28:23 AM »

Ah I see. Done.

Flickers the same as before I'm afraid.
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