Nope, they would have conflicting memory ranges and I/O ports. Someone showed a proprietary CAD graphics card with two VGA connectors some weeks back. But that would only work in Windows or with special software.

Not any two random cards, but there were dualhead cards back in the day. Miro had at least one, the miro Crystal/Magic 20 twin PCI, and they had a similar VLB card. I believe Teamware had a dualhead ISA card.

Of course these wouldn't give you dualhead in DOS, but apps (generally CAD-stuff) written to support them could use them, and I believe there were Win3.x drivers too.

Windows 98 was the first version of windows to natively support dual monitors, and even then you had to have cards that wouldn't conflict with one another. As said above, dual monitor setups were generally reserved for CAD programs and some borland IDEs.

May I ask why you want to do this? There is very little software support for dual monitors until long after the 286 era, and unless you plan to write your own software to utilize the monitors there is really no point to doing so.

I used VGA plus a Hercules card back in the day to be able to code and debug simple games, first in Turbo C then later in C++ using DJGPP and gdb. That was pretty useful and worked reasonably well.

I'm planning to build a 286 and a 486 system; I've got the motherboards and most of the parts I need.
I intend building custom cases.
At work, they were throwing out cardboard product features that had built-in LCD displays, and my boss let me have them. One is 9", one is 6" and one is 5" (ro maybe 4", I forget).

I thought it might be a neat idea, when building the cases, to install one of the small LCDs as a system monitor display or a second monitor.
What I can still do is install the LCDs with their controller boards into the front of the cases, put my own custom mpg videos on the LCD controllers, and display that in the case front.

But I would have rather been able to use the small display. What gave me the idea was watching either an LGR or an 8-Bit-Guy video about the Roland MT32, which displayed a custom message on its LCD when Space Quest started playing on the connected computer.

dkarguth wrote:

Windows 98 was the first version of windows to natively support dual monitors, and even then you had to have cards that wouldn't conflict with one another. As said above, dual monitor setups were generally reserved for CAD programs and some borland IDEs.

May I ask why you want to do this? There is very little software support for dual monitors until long after the 286 era, and unless you plan to write your own software to utilize the monitors there is really no point to doing so.

root42 wrote:

Nope, they would have conflicting memory ranges and I/O ports. Someone showed a proprietary CAD graphics card with two VGA connectors some weeks back. But that would only work in Windows or with special software.

yep
http://retronn.de/imports/hwgal/hw_n9_gxitc_front.html

Okay, I was watching 8-Bit Guy talk about building his dream computer on YouTube today, and he talked about the "Gameduino".
Now this looks like something I might could use to talk to a 2nd, built-in display on a 286 or 486...

The question still is... how would I talk to it from the computer?

Here's the Arduino page on it:
http://playground.arduino.cc/Main/Gameduino

Would it be possible to interface it to a second parallel port (LPT2) or 2nd (3rd?) serial port?

I really hate the idea of attaching a pi zero(W) to the case display and talk to that from the PC. Using a more powerful computer for a 286 to talk to a 6" LCD? Uhm. No.

If I wanted to just interface, say, a simple b/w character LCD to my 286, how would I go about it?

Maybe I need to search the forums for "Arduino" and see if anybody else has tried this kind of thing.

You can use the parallel port to interface with SPI. You need 4 pins for SPI, which would be one nibble of every byte you send to the parallel port. Should be relatively straightforward.

See also here:

http://michaelgellis.tripod.com/parallel.html

https://www.seasip.info/VintagePC/dualhead.html

Very good source of information

Hamby wrote on 2019-02-05, 20:23:

I know on old x86 to 486 systems you can have both a VGA and a mono adapter and use two monitors.

But is there any way to have two VGA displays (showing different content) on a 286-486 system?

Time for necroposting)))
COLORGRAPHIC TWIN TURBO drivers and manual?