Multisync monitor option in early VGA cards

[musicforlife]

I have this early 8-bit VGA card called Paradise Pvga. It contains dip switch settings for:

- Switch 1 Monitor Type. ON: Multi frequency, OFF: Standard VGA
- Switch 2 VGA Mode Switching Style. ON: PS/2 Style - All modes available on all monitors, OFF: PC/AT Style - color on color, mono on mono
- Switch 3 Not used - Set to OFF
- Switch 4 (Not VGA Plus) 8bit vs 16bit AutoSense. ON: Auto sense 8/16bit BIOS access, OFF: Force 8bit BIOS access


I know that in early days when VGA just came, they manufactured several multisync monitors in order to be fully compatible with all the available options from digital rgbi to analog vga to handle varying setup changes.

I have 14" multisync CRT hence I'm tempted to use the Multisync option in the card but since there's no documents available about what it actually does, I am all the time wondering: What is the actual signal (vertical & horizontal sync amount) it outputs? Also are there any benefits to use multisync option instead of standard 31Khz VGA? I mean, if multisync monitors like mine can handle standard VGA, then why to include such option in first place?

I have also seen multisync monitor option in Tseng ET3000AX combo cards and many other early cards and I wonder does their multisync signal differ from each other?


Also, in paradise card the second switch says " ON: PS/2 Style - All modes available on all monitors, OFF: PC/AT Style - color on color, mono on mono". What does this actually mean???

 

[krebizfan]

The multisync modes can get you higher than VGA resolutions like 800x600 and even 1024x768 (if the monitor allows) plus some crazy 132 column text modes. Don't bother with the latter; those text modes are hard to read.

Some Paradise cards came with a program to fake other display types more accurately.

IIRC, PS/2 systems could run color VGA displays in monochrome grey styles which the AT VGA adapter didn't do. I am not sure if Paradise was using terminology to reflect this.

 

[Xacalite]

Your card is most likely Paradise VGA Plus, with PVGA1A chipset and 256 KB of RAM.
It supports one super VGA mode: 58h, ie. 800x600x16, and for this needs a multisync monitor.
I suspect that with SW1 set to standard VGA that mode is unavailable.

 

[kgober]

Your card is most likely Paradise VGA Plus, with PVGA1A chipset and 256 KB of RAM.
It supports one super VGA mode: 58h, ie. 800x600x16, and for this needs a multisync monitor.
I suspect that with SW1 set to standard VGA that mode is unavailable.

I concur. In this context "multi frequency" refers to a monitor that can do VGA plus SuperVGA. At that time there were a lot of fixed-frequency VGA monitors that could only handle 640x480, and attempting to run those at another frequency risked causing damage to them. So this switch would have blocked the card from generating frequencies your monitor couldn't handle (i.e. you had to specifically identify your monitor as "800x600 capable" using this switch).

Eventually higher resolutions like 800x600 and 1024x768 became so common and expected that all VGA monitors were expected to be multi-frequency, but it's easy to forget that this wasn't always the case.

 

[musicforlife]

Your card is most likely Paradise VGA Plus, with PVGA1A chipset and 256 KB of RAM.
It supports one super VGA mode: 58h, ie. 800x600x16, and for this needs a multisync monitor.
I suspect that with SW1 set to standard VGA that mode is unavailable.

I recall that's not true. I was using standard VGA setting and I was still able to put SVGA in Windows 3.1. I could test this later to confirm.

 

[Trixter]

Any mode with more than 480 lines requires a "multisync"/SVGA monitor. So either the SVGA mode you were using in Windows 3.1 was 640x480, or the Windows driver is ignoring whatever the DIP switch setting is (if you had it set to standard VGA).

 

[rmay635703]

Any mode with more than 480 lines requires a "multisync"/SVGA monitor. So either the SVGA mode you were using in Windows 3.1 was 640x480, or the Windows driver is ignoring whatever the DIP switch setting is (if you had it set to standard VGA).

Under Windows 3.0 I vaguely recall getting a special hacked driver so I could display 800x560 using my standard VGA equipment.

Seemed to work, not sure why it wasn’t the full 600 lines though.
but the image on screen seemed tall and squished

 

[2icebitn]

Under Windows 3.0 I vaguely recall getting a special hacked driver so I could display 800x560 using my standard VGA equipment.

Seemed to work, not sure why it wasn’t the full 600 lines though.
but the image on screen seemed tall and squished

Maybe the refresh rate was lowered to accomodate higher vertical resolution. That's where the hacking came in. It was probably 560 lines because the original NEC M* and M* II was only rated up to 560 lines. Iirc Sony was the very next company to release a m* and there's could do 600 lines.

Nothing is absolutely etched in stone. Everything has some variability. Back in the day people were hacking CGA monitors to accept EGA signals. Not every monitor could do it though.

 

[musicforlife]

Any mode with more than 480 lines requires a "multisync"/SVGA monitor. So either the SVGA mode you were using in Windows 3.1 was 640x480, or the Windows driver is ignoring whatever the DIP switch setting is (if you had it set to standard VGA).

Oh, I forgot to mention the main thing. I am not actually bothered about the SVGA thing in windows but in dos, when multisync option is set, none of my semi-modern VGA screens are able to view that signal even though they can go lower than 60hz refresh rate hence this makes me wondering what kind of weird non-standard resolution multisync is producing here.

 

[Xacalite]

I have a similar card - 8-bit, based on PVGA1A, with FCC id: DBM5UEPS2V00001, apparently Philips OEM variant.
Connected it to a typical SVGA monitor, and did some tests...

SW1 set to "standard VGA" - all modes work as expected, except for 58h (800x600x16) where monitor goes into power saving mode

SW1 set to "multifrequency":
- text mode - monitor gets out of sync, measures the frequencies as 27.9 kHz / 62 Hz
- 200-line graphics modes - 31.5 kHz / 62 Hz
- 350-line graphics modes - 31.5 kHz / 62 Hz
- 480-line graphics modes - 31.5 kHz / 60 Hz

I don't understand it... perhaps this way it's supposed to be more compatible with CGA/EGA? You know, they are 60 Hz, and VGA displays 200- and 350-line modes at 70 Hz, causing problems with some timing-sensitive software.
But why such a weird frequency for text mode?

 

[Xacalite]

Maybe the refresh rate was lowered to accomodate higher vertical resolution. That's where the hacking came in.

Exactly.
Search for "svgabg55.zip", run VGADEMO.EXE -> Tweak16 -> 800x600x16
Yes, even a plain VGA can be tweaked into 800x600, but the frequencies are 29.3 kHz / 45 Hz, making it pretty much useless.

 

[musicforlife]

I have a similar card - 8-bit, based on PVGA1A, with FCC id: DBM5UEPS2V00001, apparently Philips OEM variant.
Connected it to a typical SVGA monitor, and did some tests...

SW1 set to "standard VGA" - all modes work as expected, except for 58h (800x600x16) where monitor goes into power saving mode

SW1 set to "multifrequency":
- text mode - monitor gets out of sync, measures the frequencies as 27.9 kHz / 62 Hz
- 200-line graphics modes - 31.5 kHz / 62 Hz
- 350-line graphics modes - 31.5 kHz / 62 Hz
- 480-line graphics modes - 31.5 kHz / 60 Hz

I don't understand it... perhaps this way it's supposed to be more compatible with CGA/EGA? You know, they are 60 Hz, and VGA displays 200- and 350-line modes at 70 Hz, causing problems with some timing-sensitive software.
But why such a weird frequency for text mode?

But CGA or 200-line EGA is 15.7 Khz and 350-line EGA is 21.8 kHz so I don't think EGA monitor could stretch into 27Khz

 

[krebizfan]

But CGA or 200-line EGA is 15.7 Khz and 350-line EGA is 21.8 kHz so I don't think EGA monitor could stretch into 27Khz

ATI EGA Wonder would output 640 by 480 graphics modes and also had text formats with many, many columns. Needs a multi-sync monitor and I presume a higher kHz. I can't find a source detailing the signal specifics for this.

 

[Xacalite]

But CGA or 200-line EGA is 15.7 Khz and 350-line EGA is 21.8 kHz so I don't think EGA monitor could stretch into 27Khz

Exactly.
It would be logical for the card to output 15.7 kHz for 200-line modes, 21.8 for 350-line, and 31.5 for 480-line. And 27.9 kHz might be logical for 400-line, ie. VGA text modes.
But this card doesn't behave this way.

BTW: you mentioned some success with the 800x600 mode - what kind of monitor were you using?

 

[rmay635703]

Exactly.
It would be logical for the card to output 15.7 kHz for 200-line modes, 21.8 for 350-line, and 31.5 for 480-line. And 27.9 kHz might be logical for 400-line, ie. VGA text modes.
But this card doesn't behave this way.

BTW: you mentioned some success with the 800x600 mode - what kind of monitor were you using?

Under Windows 3 I used an old plain VGA Tandy VGM monitor with 800x560 using a generic VGA card

I never noticed any real flicker and used the screen several years after we sold our name brand machine to get a generic tower.

 

[Chuck(G)]

Flicker is a highly personal thing. CRT TV, if viewed by my peripheral vision flickers noticeably. LED Christmas lighting flickers intolerably for me. If I view a hillside filled with homes with mixed incandescent and LED Christmas lighting, I can pick out every LED string from a half-mile away. The reason is simple--Christmas LED strings are fed from the 60Hz line frequency with little or no persistence between half-wave cycles. Most inexpensive LED strings divide the string into two parts, with each half lighting on alternate half-cycles.

 

[bobba84]

I know the feeling - but here we run on 50Hz, so it's worse. I've been to people's houses that have (cheap) LED lights inside, and they gave me a headache.

 

[musicforlife]

Exactly.
It would be logical for the card to output 15.7 kHz for 200-line modes, 21.8 for 350-line, and 31.5 for 480-line. And 27.9 kHz might be logical for 400-line, ie. VGA text modes.
But this card doesn't behave this way.

in Windows 3.1, I was able to get Super VGA in both standard and multisync mode, weird. Anyway, you also forget that both CGA and EGA uses digital RGBI while analog VGA is not able to produce that hence you can't have multisync option to be used for EGA monitor.

BTW: you mentioned some success with the 800x600 mode - what kind of monitor were you using?

I am using 14" CRT multisync monitor which is capable of both analog VGA/RGB and digital RGBI with horizontal sync 15-35Khz.

 

[Xacalite]

Anyway, you also forget that both CGA and EGA uses digital RGBI while analog VGA is not able to produce that hence you can't have multisync option to be used for EGA monitor.

I don't expect this card to drive EGA monitor, I just point to the fact that using CGA/EGA frequencies would make the card to be more compatible with CGA/EGA timing-sensitive software.
But this card obviously doesn't output CGA/EGA frequencies, so I can't see any sense in that "multisync" setting of SW1.

I am using 14" CRT multisync monitor which is capable of both analog VGA/RGB and digital RGBI with horizontal sync 15-35Khz.

I've tried it with a typical SVGA monitor, 30-70 kHz, and 800x600 doesn't work, just goes into power saving mode, irrelevant of the SW1 setting.
Perhaps wrong sync polarity, or something...

 

[2icebitn]

Could be. I had a Sony 19" monitor a million years ago. It should have worked with a Mac, but for some reason I could never get it to sync with a PowerMacs output. Correct frequencies, correct sync parities. With my Emachines video card it would. I never found out exactly why, but I just chalked it up to sync widths. Or shape etc.