Connecting a DOS PC to a PVM

[hosser]

Hi guys,

I maintain an old DOS PC to play my old favourites like UFO: Enemy Unknown, DooM, Quake, Monkey Island etc. I realise I could just play most of these on a modern PC using DOSBox or source ports or whatever, but I am a sucker for authenticity and nostalgia so I like to play them in their original format. I don't think I need to explain that to most members of this forum!

At the moment I connect the DOS PC to my modern Dell LCD monitor, but I'd really like to see what it looks like on my PVM as I feel this would be a more authentic display for such an old machine. I've tried using a VGA > BNC cable to connect the PC to my PVM (combining the H and V sync cables with a T-shaped BNC coupler) but there's obviously an issue with the sync because the image isn't at all stable (though it does work).

After a bit more reading it seems this is due to the PC outputting 31KHz signal rather than the 15Khz expected by the PVM? Please correct me if I'm wrong. I also have no idea what resolution the DOS command-line runs at.

As I understand it you can get around the scan frequency issue by using a scan converter. What I'd like to know is, would an Extron VSC 100 do the job or do I need one of the more expensive Super Emotia units?

Any advice greatly appreciated.

[kamiboy]

Old DOS mode 13h games like DooM run in a very strange resolution. I doubt you can find anything that can convert it into something that a SONY monitor can display.

Your best bet is using an old Pac graphics card with S-video out. That will work, but look pretty crappy.

[Fudoh]

At the moment I connect the DOS PC to my modern Dell LCD monitor, but I'd really like to see what it looks like on my PVM as I feel this would be a more authentic display for such an old machine.

Starting in the late 80s, these titles were meant to be output on a 31khz display, so I wouldn't call a PVM more authentic.

DOS (boot/prompt) is 400p70 and MCGA/VGA games are 200p70. A Extron VSC unit will convert that for you into 480i60, but you're adding interlacing and it won't look great.

[hosser]

Good info chaps - thanks very much. I guess I will just keep using my LCD then.

[BONKERS]

You would be far better off tracking down old CRT 31khz PC monitors.

[BuckoA51]

You could always look for an old VGA CRT monitor.

[hosser]

Yeah, I think there's one at work I can have actually, I was just hoping I could use an existing display in my setup and not add another bulky CRT to it. Another display would make four displays total in my living room, not sure I want the authenticity of a CRT that badly!

[antron]

There is a dos program called arcmon.exe that will force it to 15kHz. You can call it in your autoexec.bat. You will then need to combine the syncs.

I've run mame and many other emulators this way. I never tried anything 3d like doom. Probably won't look good.

[hosser]

There is a dos program called arcmon.exe that will force it to 15kHz. You can call it in your autoexec.bat. You will then need to combine the syncs.

I've run mame and many other emulators this way. I never tried anything 3d like doom. Probably won't look good.

Sounds interesting but seems it only supports a handful of video chipsets. Can't remember what card is in my DOS PC but pretty sure it's not one of the supported ones.

[kamiboy]

Interesting that such a tool exists, but I am not sure whether it can work for mode 13h games. I guess it depends on how the tool is programmed. Even if it does work it will prolly cause problems with games since they have been coded to run at a higher refresh rate than 60hz.

If anyone tries this I am curious to know your results.

[mvsfan]

I saw a 36" dell dimension Vga Crt monitor for sale on craigslist a while back for $200.

Something like that would be excellent for a DOS pc.... Or even a Dreamcast mabeye..???
Most of these tubes only do up to 640X480 or 800x600.

Smaller Vga crts you can find for practically nothing.

[Ed Oscuro]

That Dell 36" probably runs its maximum at HD resolution or better.

[viletim]

Interesting that such a tool exists, but I am not sure whether it can work for mode 13h games. I guess it depends on how the tool is programmed. Even if it does work it will prolly cause problems with games since they have been coded to run at a higher refresh rate than 60hz.

If anyone tries this I am curious to know your results.

I used to play DOS games like this, connected to a TV. There were several TSRs written for the propose, and I remember Mon-Arc and VGATV were the two with the best compatibility. Not all video cards are compatible, I went through a few of them before I found a good one. Mode 13h works fine (don't pretty much all early VGA games use this mode?), as do the text modes. The text mode get replaced by another one with a different font but there is not adverse affect on the software.

[mvsfan]

That Dell 36" probably runs its maximum at HD resolution or better.

I guess id have to know which monitor it was but that monitor was from the 90s and it was 4:3.

would it really be hd resolution?

[hosser]

Cool, looks nice. And this is just a DOS PC connected via an Extron Emotia? You didn't have to use any programs to force a specific resolution or anything?

Does the DOS command line display on your PVM? Is it readable?

If so I'll get an Emotia.

[Fudoh]

The Emotia is fine with all classic DOS video modes, but what I would like to know (from copados33)

- How do you accomplish the 200p to 240p mapping. Did you maximize the vertical size on the Emotia or the display ? Doesn't this hurt the quality (PVM line mapping <> pixel output). On a standard 240p signal from the Emotia I would expect the image to be letterboxed (200 active lines + 20 black ones top and bottom).

- How does the 70Hz to 60Hz conversion work out for you ? (Dos is 400p70, MCGA is 200p70)

[hosser]

It is just a DOS PC, no extra software, the Emotia takes anything up to 60-65hz 31khz and downscales it to 15khz.

And I'm not using a PVM, just a cheapo CRT TV, on a PVM it will look a look a thousand times better

Very nice. Why do you recommend the Emotia over say, a cheaper VSC 100 unit from the same company? Does it support something that the VSC 100 does not? Thanks.

[Fudoh]

The Emotia and Super Emotia will output in true low-res 240p (means that you get proper scanlines).

All other Extron VSC units and units like the Emotia Xtreme or Super Emotia II merely output in 480i. It works, but you get an interlaced output without pronounced scanlines.

[kamiboy]

The one time I used my Emotia was to connect to a X68000 and the results were horrendous. Part of the issue I think was that the Emotia mixes the wrong two scan lines together when down converting and the only way to fix that is by adding another device to the already messy chain, which I of course refused to do.

[hosser]

The Emotia and Super Emotia will output in true low-res 240p (means that you get proper scanlines).

All other Extron VSC units and units like the Emotia Xtreme or Super Emotia II merely output in 480i. It works, but you get an interlaced output without pronounced scanlines.

Ah. Thanks. I definitely want an Emotia then.

The one time I used my Emotia was to connect to a X68000 and the results were horrendous. Part of the issue I think was that the Emotia mixes the wrong two scan lines together when down converting and the only way to fix that is by adding another device to the already messy chain, which I of course refused to do.

That doesn't sound encouraging. Do you still have it?

[Fudoh]

You can find some alternatives to the Emotias here: http://scanlines.hazard-city.de/

[kamiboy]

That doesn't sound encouraging. Do you still have it?

I do, but if you ask because you are looking to acquire one I would recommend you to look elsewhere first. I want too much for my unit, and I prefer trades. I have a post about it in the trade section.

[hosser]

That doesn't sound encouraging. Do you still have it?

I do, but if you ask because you are looking to acquire one I would recommend you to look elsewhere first. I want too much for my unit, and I prefer trades. I have a post about it in the trade section.

Ah, I was actually going to ask if you had any other sources you could test it with (a DOS PC would be ideal but I realise not many people keep those around these days...). I'm really curious to see what the DOS PC > Emotia > Sony PVM setup would look like, but not curious enough to lay down the cash to find out!

[kamiboy]

I am a bit curious myself, but my Emotia is packed for shipping to a future owner, I cannot be arsed to bust it open for a test.

Not to mention my so called DOS PC, which is also packed away, and a bother to reassemble.

[hosser]

I am a bit curious myself, but my Emotia is packed for shipping to a future owner, I cannot be arsed to bust it open for a test.

Not to mention my so called DOS PC, which is also packed away, and a bother to reassemble.

Nah no worries man, I totally get that.

[kamiboy]

He he, come to think of it, my PVM/BVM's are packed away as well.

[Fudoh]

I use an old Pentium 3 with Windows 98 equipped with an Ati rage 128 AGP and run most of my DOS games from there, I do not use "real" DOS.

if you start them directly, it's still "DOS". The increased refresh rate was used to accomodate for the lower line count (200/240 and 400/480), while maintaining the 31khz standard. The 70Hz issue is one of the reason why DOSBOX emulation isn't ideal - as the underlying Windows is usually running fixed at 60Hz these days.

You need a game which runs smoothly and with locked v-sync to test the framerate conversion. Can't think of anything right now.

The resolution mapping is easy to check: if you got a game which uses a sharp 1-pixel-line font (like Doom for its weapon stats in the lower right corner) you can check if these are properly mapped to use just a single scanline on your CRT or if they're blurred across two scanlines.

[ZellSF]

I use an old Pentium 3 with Windows 98 equipped with an Ati rage 128 AGP and run most of my DOS games from there, I do not use "real" DOS.

if you start them directly, it's still "DOS". The increased refresh rate was used to accomodate for the lower line count (200/240 and 400/480), while maintaining the 31khz standard. The 70Hz issue is one of the reason why DOSBOX emulation isn't ideal - as the underlying Windows is usually running fixed at 60Hz these days.

Just want to point out that this isn't the fault of DOSBox or Windows, it's display manufacturers.

Both my LCDs can do 70hz (one through fixed refresh, other through G-Sync) and both display DOS games perfectly with DOSBox/Win8.

[hosser]

An update: Today I managed to get my DOS PC to output to my PVM

I dusted off my XRGB3 which I haven't used in a while. Connected it to my PVM with a VGA > RGBHV BNC cable and joined the H and V sync cables with a BNC T coupler. Then I enabled low screen resolutions on the XRGB3, set the output resolution to 320x240 and set the D2 input to RGBHV (yeah I'm using the D2 input on the XRGB - do I remember reading that was a bad idea? I don't have a D-Input > VGA converter so no choice at the moment).

It works. But it looks pretty bad. The command line is not very readable. Turning the LP filter off helped a bit, and setting the drawing method to non-interlace made it a little less blurry. Any sharpness setting other than 7 looks horrible. Fiddling with the screen size settings doesn't help.

I fiddled with the dot-by-dot setting a bit and the X1 setting looks amazing (I can read the text perfectly) BUT unfortunately this is because it zooms in so far, meaning you can only see the top left quarter of the screen area. So that's no good.

Anything else I can change on the XRGB to get a better picture or is this the best I am likely to get with this setup?

Photo 1 | Photo 2

[kamiboy]

Have you tried the software solution?