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EGA and VGA Card in IBM 5155?

ibmapc

ibmapc

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Please excuse my ignorance. I posted a simalar question previously regarding using CGA and VGA cards together in my 5155 and learned that the VGA would be limited to mono mode if used together with a CGA card. Does the same limitation apply if I use an ATI EGA Wonder together with a VGA card? Can the two even exist together? Is there a particular VGA Card that would work best? I'm hoping to be able to run the 5155's internal display from the EGA Wonder and have the option to connect a VGA monitor to a second adaptor. I would not need to have both displays active at the same time. Just looking for options.
 
No, EGA and VGA generally will not work together--they use the same addresses for the BIOS extension, as well as memory and I/O port addresses conflicting. Sorry. :(
 
vwestlife said:
EGA and VGA can only coexist if either one of them is operating in monochrome-only mode.
Click to expand...

If that's the case, I should be able to run the EGA Wonder in monocrome mode for the internal monitor and use VGA monitor on the VGA card in color mode . Please confirm.
 
I was under the impression that the internal monitor used a monochrome CRT but otherwise was compatible with CGA, not MDA (which uses a different scan rate). So you'd have to operate the EGA card in CGA mode.

Doesn't seem like the solution you're after.
 
Chuck(G) said:
I was under the impression that the internal monitor used a monochrome CRT but otherwise was compatible with CGA, not MDA (which uses a different scan rate). So you'd have to operate the EGA card in CGA mode.

Doesn't seem like the solution you're after.
Click to expand...

I'm hoping you're incorrect. I guess it depends on what happens to the composite out put on the EGA Wonder in mono mode.
 
OK If both cards have externally accessable dip switchs, I should be able to configure as needed. ie, I could set the EGA Wonder to drive the internal monitor and set the VGA Card to mono mode. Then, before connecting VGA monitor, I could set the EGA Wonder for mono mode (as long as it does not send a harmfull signal to the internal monitor) and set the VGA for VGA. Maybe I could put an externally accessable switch in the line to the internal monitor if needed.
 
ibmapc said:
I'm hoping you're incorrect. I guess it depends on what happens to the composite out put on the EGA Wonder in mono mode.
Click to expand...
Assuming you set the switches (or use the SuperSwitch software) appropriately, the EGA Wonder can display EGA, CGA, MDA and Hercules on an EGA, Multi-sync, RGB, 25KHz, Composite or TTL Mono monitor.
 
MikeS said:
Assuming you set the switches (or use the SuperSwitch software) appropriately, the EGA Wonder can display EGA, CGA, MDA and Hercules on an EGA, Multi-sync, RGB, 25KHz, Composite or TTL Mono monitor.
Click to expand...

Does that mean I can display 640x350 on the composite monitor in the 5155?
 
ibmapc said:
OK If both cards have externally accessable dip switchs, I should be able to configure as needed. ie, I could set the EGA Wonder to drive the internal monitor and set the VGA Card to mono mode. Then, before connecting VGA monitor, I could set the EGA Wonder for mono mode (as long as it does not send a harmfull signal to the internal monitor) and set the VGA for VGA. Maybe I could put an externally accessable switch in the line to the internal monitor if needed.
Click to expand...
As far as having both an EGA and VGA adapter installed, I'd re-read Chuck's post #2 above. AFAIK an EGA or VGA in MDA or CGA mode is still an EGA or VGA, with conflicting BIOS and I/O port adresses even when they don't share the display memory.

It ought to be a fairly simple mod to add a couple of wires and a switch to en/dis-able either one though.
 
MikeS said:
Why not just try it instead of all this speculation?
Click to expand...
Because damage to parts due to incompatibility (especially the 5155's internal monitor)is not a good thing. But, if I can get some good info here before investing time and money in parts I'll be in more of a comfort zone. I am not willing to just plug in some parts and see if it will power up wthout smoking. I've owned the 5155 since new and have managed to keep from killing it. I'm trying to see how far I can upgrade it without detracting from it's value.
 
I don't see why you don't just stick with a VGA. It can go backwards to EGA. Just get an off-the-shelf VGA to TV type converter and you can drive the internal monitor. It'll be a bit blurry in any resolution above 640x200, but it'll work. I ran a 5155 with this setup years ago ... at one point I even put a Pentium 166 in the case (I know, desecration!) and played Duke Nukem 3D in shades of amber. Windows 95 in 640x480 was actually usable using one of the high contrast color sets. The only fault seemed to be if there was an "excessive" amount of full intensity color, but that may have been due to poor cable quality or something... and that was just a bit of vertical distortion. The 5155 monitor is basically a standard composite signal displayed in monochrome. You could run a TV projection through it (one of my original experiments.)

Also: Most cards are not designed to have their dips thrown while powered, so you don't want to do that.
 
Okay, I pulled out the PC O&A for the IBM Portable Personal Computer Display. It's short--just a page of specs and 2 pages of schematics. But it says:

Composite Video Signal:
  • 1.5 Vdc (peak to peak)
  • 60 Hz refresh rate
  • 15.75 KHz horizontal scan rate
Click to expand...

And there you have it--it accepts CGA signals. By comparison, MDA/HGC video is 50 Hz vertical, 18.432 KHz horisontal. If you try to drive your monitor with an MDA signal, it won't work. You may not ruin your display, but you won't get anything intelligible from it either.

If you want to extend the capabilities, consider adding a PGC, Hercules InColor or 8514/A. Maybe a TIGA card would also work.

See:

http://www.seasip.info/VintagePC/dualhead.html
 
southbird said:
I don't see why you don't just stick with a VGA. It can go backwards to EGA. Just get an off-the-shelf VGA to TV type converter and you can drive the internal monitor. It'll be a bit blurry in any resolution above 640x200, but it'll work. I ran a 5155 with this setup years ago ... at one point I even put a Pentium 166 in the case (I know, desecration!) and played Duke Nukem 3D in shades of amber. Windows 95 in 640x480 was actually usable using one of the high contrast color sets. The only fault seemed to be if there was an "excessive" amount of full intensity color, but that may have been due to poor cable quality or something... and that was just a bit of vertical distortion. The 5155 monitor is basically a standard composite signal displayed in monochrome. You could run a TV projection through it (one of my original experiments.)


Also: Most cards are not designed to have their dips thrown while powered, so you don't want to do that.
Click to expand...

How big is the converter. Can it be housed within the case?
 
ibmapc said:
How big is the converter. Can it be housed within the case?
Click to expand...

There's a million and one of them out there. But I do have one that was intended to be powered by USB (it doesn't NEED USB, it just took the +5V from it), and it was only about the dimensions of a business card and about an inch tall, so yeah, it could totally be wired to the power supply and contained within. The only "problem" you have to deal with is it will still come out of the machine to hook to the external VGA port (but that's where you come up with a clever right-angle connector or something.) When I put the P166 board in, I had a VGA with a built-in TV out port, so that was a lot easier to rig than a full VGA cable. But I don't know of any ISA cards similarly configured (not to say they don't exist, I just don't know of them.)
 
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