This card produces a 56Hz output in 800x600 from what I remember, LCDs tend to be quite picky with what they'll display and many ISA cards output timings many LCDs are not particularly fond of, especially low end things like these Tridents.

Tiido wrote on 2023-05-28, 01:14:

This card produces a 56Hz output in 800x600 from what I remember, LCDs tend to be quite picky with what they'll display and many ISA cards output timings many LCDs are not particularly fond of, especially low end things like these Tridents.

Is there a way to force the card outputs a certain refresh rate? I found an article about this, but it didn't work. Beside this, I really don't understand the logic behind it. When the card output 640x480 256 color to the LCD, the LCD detects that the refresh rate is exactly 59hz. What in the earth is the reason that it can output 59hz when in 640x480 but can not do the same in 800x600 mode. It's only 3hz lower than 59hz, not a big difference. I cannot think of it being unable to produce that 3hz more frequencies to make the LCD happy.

It's possible the card is configured for 800x600 with interlace.
Try SVM.EXE - AFAIR there are options to test various refresh rates and interlace settings.

Also, are you sure that card has 512 KB of RAM?
It looks weird...
4 x 41256 = 128 KB
I don't know about those IBM chips, but they may be 41256 equivalents, so another 128 KB, and that would be 256 KB total - but that's not enough for 640x480x256...

GunKneeNeon wrote on 2023-05-28, 12:05:

Beside this, I really don't understand the logic behind it. When the card output 640x480 256 color to the LCD, the LCD detects that the refresh rate is exactly 59hz. What in the earth is the reason that it can output 59hz when in 640x480 but can not do the same in 800x600 mode. It's only 3hz lower than 59hz, not a big difference. I cannot think of it being unable to produce that 3hz more frequencies to make the LCD happy.

The LCD info is probably rounding down, 640x480 is usually 59.94fps which is practically 60fps while 56fps is significantly different.

Grzyb wrote on 2023-05-28, 13:31:

It's possible the card is configured for 800x600 with interlace.

I cannot find the jumper settings specifically for my card anywhere, but here is a topic for 8900D which has a very similar jumper layout to mine. The jumpers settings in the manual says J7(open) is for non-interlaced monitors. I had my J7 open as well, see the picture I posted before.

Grzyb wrote on 2023-05-28, 13:31:

Try SVM.EXE - AFAIR there are options to test various refresh rates and interlace settings.

Input not supported when select 800x600-256 NI(the three 800x600-256 modes have the same result).

Grzyb wrote on 2023-05-28, 13:31:

Also, are you sure that card has 512 KB of RAM? It looks weird... 4 x 41256 = 128 KB I don't know about those IBM chips, but the […]
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Also, are you sure that card has 512 KB of RAM?
It looks weird...
4 x 41256 = 128 KB
I don't know about those IBM chips, but they may be 41256 equivalents, so another 128 KB, and that would be 256 KB total - but that's not enough for 640x480x256...

The test result of the Tellset utility:

The BIOS info screen when booting up:

OK, I'm inclined to believe those IBM 90x0711 chips are 256K x 3-bit.

Does 800x600 16-color work with your monitor?
And how about 1024x768 ?

Grzyb wrote on 2023-05-28, 16:29:

Does 800x600 16-color work with your monitor?
And how about 1024x768 ?

Yes, in SVM they both worked. Though 1024x768-16 showed a low quality image with vertical green lines in it.
In Windows 95, again the 800x600-16 mode worked, however when selecting 1024x768, the color palette option automatically turned into 256-color, which obviously wouldn't work. This was with the Windows' stock Trident Super VGA driver. With Trident Chip for ISA/VSL V1.0 driver, there was only 256-color option under color palette.

TVGA9000C supports two non-interlaced 800x600 256-color modes:

Not sure how to select them... TVGACRTC.EXE may be the proper tool.

Grzyb wrote on 2023-05-28, 17:09:

Not sure how to select them... TVGACRTC.EXE may be the proper tool.

Ahh.... We've made a progress here. See my picture of the TVGACRTC utility. The frequencies from 75.0-98.0MHz are supported, which correspond the refresh rates from 58.41-76.32Hz respectively. All divided by 1.

However, the images are not correct like this one.

How do you know those frequencies are supported for that board? They are rather high for an old ISA card.
Typically the pixel clock for 800x600@60fps would be 40MHz...

jmarsh wrote on 2023-05-28, 19:07:

How do you know those frequencies are supported for that board? They are rather high for an old ISA card.

Well, I'm not saying the board support that. I'm saying such refresh rates are supported by my LCD. Only rates in this scope output images to my monitor.

None of the frequencies in the left column produce an image at all on the LCD?

jmarsh wrote on 2023-05-28, 19:27:

None of the frequencies in the left column produce an image at all on the LCD?

Yes, any refresh rate out of 58.41-76.32Hz generates an Input not supported error and a blank screen.

The datasheet can be downloaded from http://www.vgamuseum.info/index.php/component … ident-tvga9000c

For 800x600x256 NI, the highest pixel clock listed is 50.3 MHz...

Grzyb wrote on 2023-05-28, 19:37:

For 800x600x256 NI, the highest pixel clock listed is 50.3 MHz...

50.3MHz only corresponds to 39.21Hz refresh rate. Does that mean what supported by the VGA is not supported by the LCD and vice versa?

I've tested the frequency range with 800x600-16 mode, the board can produce acceptable image when set to 98MHz Divided by 2, result in 76.56Hz fresh rate. Does that mean the board can work at 98Mhz(at least temporarily)?

GunKneeNeon wrote on 2023-05-28, 19:48:

50.3MHz only corresponds to 39.21Hz. Does that mean what supported by the VGA is not supported by the LCD and vice versa?

I'm lost...
According to the datasheet, 50.3 MHz pixel clock corresponds to 72 Hz VSYNC.

Something's wrong... misconfigured jumpers? Mismatched software?

Grzyb wrote on 2023-05-28, 20:01:

I'm lost... According to the datasheet, 50.3 MHz pixel clock corresponds to 72 Hz VSYNC. […]
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GunKneeNeon wrote on 2023-05-28, 19:48:

50.3MHz only corresponds to 39.21Hz. Does that mean what supported by the VGA is not supported by the LCD and vice versa?

I'm lost...
According to the datasheet, 50.3 MHz pixel clock corresponds to 72 Hz VSYNC.

Something's wrong... misconfigured jumpers? Mismatched software?

I'm also confused that the default frequency selected by TVGACRTC in 800x600-256 mode is 72.0MHz, which corresponds to 56.07Hz refresh rate. That's not supported by my LCD. However, with 36.0Mhz selected in 800x600-16 mode which corresponds to 56.25Hz refresh rate, it works! WTF!

As for the jumper configuration, I never find a doc specifically for TVGA9000C. Well, not really, here is the doc about 9000C, but it seems not for this card. Because the card doesn't have jp3-jp5.

PS: Sorry to post so many screenshots, the site doesn't allow me to copy the text. The whole doc is here. The TVGA9000 part is more reasonably.

I think the app is lying to you and configuring for 800x600x256 interlaced rather than non-interlaced.

There was this problem with earlier Tridents:

1The Trident 8800 chips have a problem with 256 color modes, as they always double
2the pixels output in 256 color mode. Thus a 640x400 256 color mode (5Ch) actually
3uses a 1280x400 frame, requiring at least a multi sync monitor.
4This problem is fixed on the 8900.

With 16 colors, 36 MHz pixel clock = 56 Hz refresh rate...
With 256 colors, a pixel actually needs 2 clock cycles, so the same refresh rate requires 72 MHz pixel clock...

That would make perfect sense, but 8800 and 9000C are completely different chips, the latter is newer and shouldn't have that limitation.

Again, must be something wrong with configuration and/or software, something that makes it behave like the 8800.