VOGONS


Reply 20 of 43, by Jo22

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Yes.

Gustavo wrote on 2022-10-15, 17:54:
Grzyb wrote on 2022-10-15, 13:01:

What VGA card you have in that Turbo XT?
Chances are, it supports register-level CGA compatibility mode...

Trident T8900D or 9000B, don´t remember now.

But the utility I mentioned sets the VGA card to 480 line mode to obtain a 60Hz refresh. That´s the reason 320x200 games get squashed.

There's an utility for Trident 8900 and it does support CGA mode.
It's called DMODE.EXE, afaik.

https://archive.org/details/Trident-TVGA-8900 … ty-Drivers-Disk

Edit: This source is even better, afaik. 😉

http://vogonsdrivers.com/index.php?catid=37

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Reply 21 of 43, by Grzyb

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7F20 wrote on 2022-10-15, 18:28:

All VGA modes are vertically line-doubled.

Not all.
Only those with 200 lines.

Nie tylko, jak widzicie, w tym trudność, że nie zdołacie wejść na moją górę, lecz i w tym, że ja do was cały zejść nie mogę, gdyż schodząc, gubię po drodze to, co miałem donieść.

Reply 22 of 43, by Jo22

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Grzyb wrote on 2022-10-15, 23:41:
7F20 wrote on 2022-10-15, 18:28:

All VGA modes are vertically line-doubled.

Not all.
Only those with 200 lines.

I assume that 7F20 meant to say that VGA doesn't normally go as low as to output signals with merely just 200 lines.
Ie. That x200 is automatically line doubled as x400, at least.

Personally, I think it's alternatively also possible to make use of the 400 lines directly, without the line doubling. Then it's 320x400 natively, so to say. With the extra lines increasing resolution of pictures etc.

However, I don't know what happens with "tweaked" VGA modes such as 320x199 (Jazz Jackrabbit menu?) or 320x240 (ModeX), though.
Does VGA output them unaltered? Or as 320x480? 🤷‍♂️
I mean, I know that VGA's CRTC is very flexible.
It can be reprogrammed to NTSC/PAL timings, even (50/60Hz, 15KHz).
Some people connected SCART TVs to VGA, even. .

Please forgive my ignorance. I've never really experimented with those tweaked modes.
My VGA interests in the 90s was more focused on mode 12h, 640x480 in 16c.
That's what productive applications, GUIs, shareware games, simulators and Quick Basic/Turbo Pascal programs used. 😅

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 23 of 43, by maxtherabbit

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Jo22 wrote on 2022-10-16, 00:16:
I assume that 7F20 meant to say that VGA doesn't normally go as low as to output signals with merely just 200 lines. Ie. That x2 […]
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Grzyb wrote on 2022-10-15, 23:41:
7F20 wrote on 2022-10-15, 18:28:

All VGA modes are vertically line-doubled.

Not all.
Only those with 200 lines.

I assume that 7F20 meant to say that VGA doesn't normally go as low as to output signals with merely just 200 lines.
Ie. That x200 is automatically line doubled as x400, at least.

Personally, I think it's alternatively also possible to make use of the 400 lines directly, without the line doubling. Then it's 320x400 natively, so to say. With the extra lines increasing resolution of pictures etc.

However, I don't know what happens with "tweaked" VGA modes such as 320x199 (Jazz Jackrabbit menu?) or 320x240 (ModeX), though.
Does VGA output them unaltered? Or as 320x480? 🤷‍♂️
I mean, I know that VGA's CRTC is very flexible.
It can be reprogrammed to NTSC/PAL timings, even (50/60Hz, 15KHz).
Some people connected SCART TVs to VGA, even. .

Please forgive my ignorance. I've never really experimented with those tweaked modes.
My VGA interests in the 90s was more focused on mode 12h, 640x480 in 16c.
That's what productive applications, GUIs, shareware games, simulators and Quick Basic/Turbo Pascal programs used. 😅

Jazz's custom mode is still line doubled. The OSSC reports it as 527 total lines (including vertical blanking).

31.46kHz line rate, 59.71Hz frame rate

Reply 24 of 43, by Gustavo

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sofakng wrote on 2022-10-13, 20:16:
Does anybody know if it's possible to output 320x200 (EGA) on a VGA card? […]
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Does anybody know if it's possible to output 320x200 (EGA) on a VGA card?

If I understand correctly, VGA cards doublescan the output resolution so 320x200 is output as 640x400 (confirmed on my PC monitor and scalers).

I'm testing an upscaler (DExx, from the creator of the OSSC) which can upscale to 1440p to 640x400p is too much for the scaler to handle. However, 240p is fine.

(I'm also using a weeCee x86 if that makes a difference...)

I´m sorry but, only now, I understand what you meant.

All you need is to set VGA modes in your card to 15.7Khz. That is the important value, the horizontal frequency. It is used by, now old, video equipment: VCRs, DVDs, TV broadcasting etc, and is capable of up to 240 lines of visible resolution at 60 fps (480 interlaced/30fps);

There are TSR utilities for DOS that do that. I couldn´t find many, most is very old software, but you may get lucky with this one:

https://github.com/reenigne/reenigne/tree/master/vga_157

UPDATE:
found another one:

VGATV for DOS driver The original driver, made for MS-DOS back in 1997.
Notice that VGATV´s default is PAL (50hz), not NTSC timing. Checkout the command line switches in .TXT file.

http://mirrors.arcadecontrols.com/VGATV/pwp.n … /dosDriver.html

Reply 25 of 43, by Grzyb

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Jo22 wrote on 2022-10-16, 00:16:

However, I don't know what happens with "tweaked" VGA modes such as 320x199 (Jazz Jackrabbit menu?) or 320x240 (ModeX), though.
Does VGA output them unaltered? Or as 320x480? 🤷‍♂️

The minimum for VGA monitors is 350 lines.
So, anything below that must be double-scanned.

Nie tylko, jak widzicie, w tym trudność, że nie zdołacie wejść na moją górę, lecz i w tym, że ja do was cały zejść nie mogę, gdyż schodząc, gubię po drodze to, co miałem donieść.

Reply 26 of 43, by 7F20

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Jo22 wrote on 2022-10-16, 00:16:
Grzyb wrote on 2022-10-15, 23:41:
7F20 wrote on 2022-10-15, 18:28:

All VGA modes are vertically line-doubled.

Not all.
Only those with 200 lines.

I assume that 7F20 meant to say that VGA doesn't normally go as low as to output signals with merely just 200 lines.
Ie. That x200 is automatically line doubled as x400, at least.

Not only that, but 240 is always 480, and 300 is output as 600 lines. But yeah, 640x480 is obviously not doubled to 960!

Reply 27 of 43, by mkarcher

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7F20 wrote on 2022-10-18, 01:06:

Not only that, but 240 is always 480, and 300 is output as 600 lines. But yeah, 640x480 is obviously not doubled to 960!

There is no standard mode with 240 lines, but yes, custom modes with 240 lines work by double-scanning into 480 lines, which is a supported mode. There also is no standard mode with either 300 lines or 600 lines (800x600 would be Super VGA). Modes with 350 lines (EGA mode 640x350; Text modes downgraded to EGA resolution) are also not double-scanned to 700 lines.

Reply 28 of 43, by kdr

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The EGA mode (640x350) on a VGA monitor is especially interesting, because the VGA card produces a 449 line frame which is exactly the same as the 449 line frame used for the 720x400 text mode, except for different polarity on the sync pins. This triggers a circuit in the VGA monitor that boosts the vertical size of the picture - if it weren't for this special circuit the EGA mode would have enormous black bars on the top/bottom of the screen and wouldn't be shown in the correct aspect ratio.

Reply 30 of 43, by maxtherabbit

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sofakng wrote on 2022-10-19, 00:00:

I’m going to try some of the utilities mentioned but I’m confused how any of the tools can force 15 kHz when it sounds like everybody is saying VGA is always line doubled?

I'm not sure what exact register twiddling it does, but VGATV 100% works. I've played many a game on my RGB monitor (15kHz only)

Reply 31 of 43, by Gustavo

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sofakng wrote on 2022-10-19, 00:00:

I’m going to try some of the utilities mentioned but I’m confused how any of the tools can force 15 kHz when it sounds like everybody is saying VGA is always line doubled?

It intercepts the BIOS calls and uses a modified video mode. I´ll post the README from the second utility:


--- The program -----------------

This program allows you to use your TV as a monitor, given that you use the
proper hardware to connect your VGA to the output equipment.

The driver is a TSR (Terminate and Stay Resident) which will try to make
sure your VGA card is, at all times, properly programmed for TV timings, which
are quite different from VGA standards:

- Standard VGA timings are normally 31.469KHz horizontal frequency, and
70.08Hz vertical frequency. Non-interlaced.

- PAL and NTSC are interlaced. PAL (Phase Alternating Line) has a horizontal
frequency of 15.625Khz and 50Hz vertical frequency. NTSC (National
Television Standards Committee) has 15.750Khz and 60Hz respectively.

There will be programs which won't work well, others won't work at all,
because they either use an unsupported video mode, or program the video card
directly, after they've set the mode. Plus, some chipests aren't fully or at
all supported.

Supported resolutions so far: due to the way the program works, resolutions
"per si" are not supported, but rather widths, heights and combinations among
them. This makes the driver more flexible among different SVGA chipsets.
Because of the number of values supported, I won't discriminate them here.
You can find however, a compatibility table on the web site. This table is by
no means complete. More than likely the video cards featured could support
more video modes under VGATV, not to mention other chipsets (albeit with no
interlace support).

Note that since NTSC has less vertical resolution than PAL, modes above 480
lines appear more overscanned than PAL.

--- The requirements ------------

For this to work, you need the following:

a) a IBM PC or compatible computer system (clone for short 😀. And yes,
your 4.77Mhz IBM PC will do. The PCI/AGP card detection uses 32-bit code
which won't run on 286 or less CPUs. Behaviour is undefined if for some
reason VGATV thinks you have a PCI bus on your system;

b) a VGA card. 3D cards only (like the first 3DFx's Voodoos) aren't
supported;

c) some memory to load this driver; if you can run DOS, you can run this.
To save memory, you can try loading it high. Like :

LH VGATV, in AUTOEXEC.BAT

d) an output device like a TV or 15Khz monitor.

Reply 32 of 43, by 7F20

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mkarcher wrote on 2022-10-18, 21:02:
7F20 wrote on 2022-10-18, 01:06:

Not only that, but 240 is always 480, and 300 is output as 600 lines. But yeah, 640x480 is obviously not doubled to 960!

There is no standard mode with 240 lines, but yes, custom modes with 240 lines work by double-scanning into 480 lines, which is a supported mode. There also is no standard mode with either 300 lines or 600 lines (800x600 would be Super VGA). Modes with 350 lines (EGA mode 640x350; Text modes downgraded to EGA resolution) are also not double-scanned to 700 lines.

It's possible to get 300x2=600 in 50Hz, but yeah it's not a standard mode. I was just trying to illustrate the concept of the VGA double scanning to accommodate lower vertical resolutions. And yeah, 350 is 350, but it's @70Hz.

Reply 33 of 43, by sofakng

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OK - I'm trying to run VGATV on the "weeCee" (Volaris Z9s chipset) and it detects the chipset as Tseng Labs but it the OSSC reports the signal as 263p (31.54 kHz, 119.93H) (using NTSC command-line option).

If I try to play a Sierra game (ie. PQ1 AGI), the OSSC can't sync. The OSSC LCD flashes between 263-p (63.08kHz 239.86Hz) on/off (but no video signal is sent).

Is the source for VGATV available?

Reply 35 of 43, by maxtherabbit

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sofakng wrote on 2022-10-24, 22:15:

OK - I'm trying to run VGATV on the "weeCee" (Volaris Z9s chipset) and it detects the chipset as Tseng Labs but it the OSSC reports the signal as 263p (31.54 kHz, 119.93H) (using NTSC command-line option).

If I try to play a Sierra game (ie. PQ1 AGI), the OSSC can't sync. The OSSC LCD flashes between 263-p (63.08kHz 239.86Hz) on/off (but no video signal is sent).

Is the source for VGATV available?

Oh interesting, you've found one that does the 240p120 thing

If you try a non-sierra game do you actually get 240p120 or does it still go crazy and drop sync?

I have one Tseng ET4000AX card which will also do 240p120 when you try to use VGATV with it, but it actually works during games - which is pretty damn cool on a VGA CRT since you get the big fat scanlines

Reply 36 of 43, by Jo22

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pentiumspeed wrote on 2022-10-24, 22:51:

What is the reasons running 70hz at all? chipset designers etc?

Cheers,

I assume it was for flicker free text-mode, rather than graphic mode.

Previously, IBM MDA monitors were usually made with a CRT that had long persistence green phosphor,
causing afterglow and a stable picture.

Of course, amber and paper white monochrome monitors existed, too.

But when VGA was released, it was the first IBM standard technically on par with MDA.

The high quality 80x25 text mode with 9x16 characters runs in 720x400 mode.
Well, in the 386/486 and ISA bus times, originally, at least.

Pentium PCs in the 90s started to use 640x350 or 640x480 graphics mode instead, not sure.

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"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 37 of 43, by kdr

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pentiumspeed wrote on 2022-10-24, 22:51:

What is the reasons running 70hz at all? chipset designers etc?

VGA was designed to provide a 640x480 picture at 60hz. The card generated a 525 line frame and this results in a 31.5khz horizontal sync.

IBM designed the VGA monitor as a fixed frequency device, so any additional video modes had to stick to the same 31.5khz sync as 640x480 used.

For the 400-line modes (720x400 text and 320x200 doublescanned graphics) the VGA generates a 449 line frame, which results in a 70hz vertical refresh given the fixed 31.5khz horizontal frequency.

For the 350-line mode (640x350 graphics) the VGA also generates a 449 line frame, but the sync polarity is modified which triggers a circuit in the monitor to "expand" the vertical size so that the 350 lines of active video will fill the entire screen.

Reply 38 of 43, by Jo22

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kdr wrote on 2022-10-25, 00:09:

For the 350-line mode (640x350 graphics) the VGA also generates a 449 line frame,
but the sync polarity is modified which triggers a circuit in the monitor to "expand"
the vertical size so that the 350 lines of active video will fill the entire screen.

Thank a lot of the explanation! 😃👍

Though I wonder if all RGBHV monitors had this installed.

I could be wrong, but I believe to remember that a few CRT monitors I used ran EGA modes (640x350) in a "squashed" fashion.

Or more precisely, EGA Trek.
I played that game on numerous PCs in the past decades.
And a few times, it wasn't being drawn full screen as it should be.
The aspect ratio wasn't right, I mean.

On LCD monitors (486 notebook, cheap TVs etc) it was sometimes looking compressed to no surprise, though.
Early LCD/TFT devices were kind of strange.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 39 of 43, by 7F20

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maxtherabbit wrote on 2022-10-24, 23:24:
Oh interesting, you've found one that does the 240p120 thing […]
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sofakng wrote on 2022-10-24, 22:15:

OK - I'm trying to run VGATV on the "weeCee" (Volaris Z9s chipset) and it detects the chipset as Tseng Labs but it the OSSC reports the signal as 263p (31.54 kHz, 119.93H) (using NTSC command-line option).

If I try to play a Sierra game (ie. PQ1 AGI), the OSSC can't sync. The OSSC LCD flashes between 263-p (63.08kHz 239.86Hz) on/off (but no video signal is sent).

Is the source for VGATV available?

Oh interesting, you've found one that does the 240p120 thing

If you try a non-sierra game do you actually get 240p120 or does it still go crazy and drop sync?

I have one Tseng ET4000AX card which will also do 240p120 when you try to use VGATV with it, but it actually works during games - which is pretty damn cool on a VGA CRT since you get the big fat scanlines

The AGI games are internally 160x200, so depending on the video path the output resolution might not be right or what is expected.