Using VMG-4000

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dexterslab
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Using VMG-4000

Postby dexterslab » Fri May 22, 2009 8:04 am

i've spent the last few days reading up on VGA signalling and the VMG-4000 is causing some confusion because it doesn't seem to use standard terminology to generate the display signal.

eg for VESA standard 1024x768@60hz the timings would be:
Pixel Clock: 65Mhz
Horiz
Front porch: 24
Sync pulse: 136
Back porch: 160

Vertical
Front porch: 3
Sync pulse: 6
Back porch: 29

If i put these into VMG-4000 i just get unrealistic horiz and vert frequencies that dont work, as you can see from the pic below which is the same rez the numbers are completly different (this is a profile i downloaded from some site). Can someone explain exactly what each of the boxes (shown in red) are and how they relate to the timing details above?

vmg4000.gif
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Re: Using VMG-4000

Postby dexterslab » Fri May 22, 2009 9:42 am

it's amazing what you can work out with a calculator... so i answered my own question :mrgreen:

in case anyone else needs this info, it's all detailed below:

ok here goes, lets say we want 1024x768 @ 60hz (perfect for LCD monitor)

VESA XGA Timing are:
Horiz Front porch 24
Horiz Sync pulse 136
Horiz Back porch 160
Vert Front porch 3
Vert Sync pulse 6
Vert Back porch 29

To convert to VMG timings:
Schwarzsch = Total length of black area (Front Porch+Sync Pulse+Back Porch)
Impulsstart = Start point of sync pulse (pixels or lines + Front Porch)
Impulslange = Sync pulse length (Sync Pulse)

so in this case the numbers for VMG would be (with the pixel clock set to 65Mhz):
Horiz Schwarzsch = 320
Horiz Impulsstart = 1048
Horiz Impulslange = 136
Vert Schwarzsch = 38
Vert Impulsstart = 771
Vert Impulslange = 6

Attention to sync polarity should also be noted, though i just select these to get the best picture, rarther than following the spec.

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Re: Using VMG-4000

Postby wongck » Fri May 22, 2009 3:52 pm

Don't your graphic card drivers comes with some defaults settings?
My Nova card have loads of settings and I just have to choose one.
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Re: Using VMG-4000

Postby dexterslab » Fri May 22, 2009 7:21 pm

wongck wrote:Don't your graphic card drivers comes with some defaults settings?
My Nova card have loads of settings and I just have to choose one.


the original crazydots drivers did, but nvdi doesn't

dont think i could bare to use it without nvdi, would be way too slow

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Re: Using VMG-4000

Postby wongck » Sat May 23, 2009 2:45 pm

Mmmm.... do you have any benchmark?

for my Nova card, it seems to need to disable some screen drivers of NVDI for it to work, i.e. it actually does not use NVDi but it's own VDI routines.
The develper told me that NVDI does not know how to handle the resolution ( ro was that colour -- can't remember).
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Re: Using VMG-4000

Postby dexterslab » Sat May 23, 2009 5:49 pm

never had issues with resolution, i use 1280x800x16 for most things

640x480x256 with NVDI3:

SNAP0002.gif
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Re: Using VMG-4000

Postby wongck » Sun May 24, 2009 2:27 am

Here is the benchmark from my system at 640x480 using the drivers that came with the Nova.
1200x800 is too small for me on my LCD, at 1024x768 it about right.

Image
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Re: Using VMG-4000

Postby dexterslab » Sun May 24, 2009 9:30 am

1280x800 looks pretty good on my 20" widescreen :mrgreen:

what colour depth was yours set to?

this is the same test, but in 16 colour not 256
SNAP0001.gif
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Re: Using VMG-4000

Postby wongck » Sun May 24, 2009 11:37 am

dexterslab wrote:1280x800 looks pretty good on my 20" widescreen :mrgreen:

So I only am using a 17" LCD - explains the reason why it looks small :lol:
The 640x480 was at 256. Sorry I missed that info out.
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Re: Using VMG-4000

Postby wongck » Sun May 24, 2009 3:12 pm

I noticed that your Genbench is newer than mine, so I downloaded v4.03 and tested it.
It seems to have some difference in the numbers.
My 640x480x256 seems to be even slower on this new version.
I am not sure why, may be it's what machine configuration it is comparing to.

Image
My Stuff: FB/Falcon CT63 CTPCI ATI RTL8139 USB 512MB 30GB HDD CF HxC_SD/ TT030 68882 4+32MB 520MB Nova/ 520STFM 4MB Tos206 SCSI
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