I know you can have a VGA and a mono graphics card in the same PC with two separate displays, but is there any way to have a CGA card and either a VGA or EGA card in the same pc on different displays? Both would have to be ISA cards, since we're talking PC/XT/AT (8088/8286).
No, EGA and VGA are supersets of CGA, so they use the same I/O ports and they all use int 10h BIOS extensions.
MDA and CGA work together because they were designed that way. MDA uses different I/O ports, and both MDA and CGA int 10h functionality is in the PC/XT BIOS itself, not an extension ROM on the card. Hercules also works, because it is basically MDA with a few extra I/O ports, and doesn't use any BIOS extensions.
CGA uses memory at B8000 and I/O at 3Dx
EGA set for monochrome monitor uses memory at B0000 or A0000 and I/O at 3Bx
Should work.
With VGA... hard to tell, there are many (S)VGA cards with DIP switches to set them for mono - then they should work alongside CGA, but others - probably not.
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.
This probably doesn't apply to your situation, but there's a utility that can be used with Tandy RL/TL systems to switch the video between the onboard extended CGA graphics chipset and and a VGA card. They're not simultaneously addressable as such, but you can display a static image on either monitor before switching to, and using, the counterpart.
wrote:EGA set for monochrome monitor uses memory at B0000 or A0000 and I/O at 3Bx
Should work.
In theory, yes. But only if software is actually written to use EGA monochrome, which hardly any software is.
wrote:In theory, yes. But only if software is actually written to use EGA monochrome, which hardly any software is.
For the graphics mode F - indeed, there's little software.
For the text mode 7 - there's plenty.
Also, some cards officially support coexistence with CGA, see eg. EGA Wonder 800+ - in such a case it powers up as MDA/Hercules.
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.
I actually encountered a similar conundrum last week while trying to achieve better CGA support with an S3 Virge/GX. The palette wouldn't switch so Wizardry looked pretty bad. Obviously, running a CGA card alongside the VGA card doesn't work, but I did have an ATI CGA Wonder available. That card has a monchrome and CGA mode selector, as well as a CGA/monochrome monitor selector. So, running it in tandem with a VGA card I was able to run it as a Hercules card. I yanked the BIOS chip from the Virge, set the CGA Wonder to CGA mode, and voila, better CGA support.
For the more technically informed on such shenanigans, will I always need to remove the BIOS chip for this or can I install a switch to connect/disconnect a handful of power/VCC pins? Will that cause any issues with phantom power reaching the BIOS? Might I burn the apartment building to the ground?
I spend my days fighting with clunky software so I can afford to spend my evenings fighting with clunky hardware.
wrote:For the text mode 7 - there's plenty.
Yea, but that's MDA mode. Why bother putting an EGA card in your system for just that? A simple MDA/Hercules clone will be fine.
wrote:For the more technically informed on such shenanigans, will I always need to remove the BIOS chip for this or can I install a switch to connect/disconnect a handful of power/VCC pins?
These are BIOS extension ROMs, and the motherboard BIOS will scan for these ROMs at startup, and execute their initialization routine when found.
So you'll need to reboot the machine after you switch the BIOS on/off.
But I suppose it might work if you put a switch on some power pins, as long as you only switch when the machine is powered off.
When there's no power on the ROM, the motherboard BIOS will not detect the extension ROM, so the VGA BIOS won't initialize the card and install its int 10h handler.
(I take it your Virge is a PCI card? That might explain why it works... I don't think it would work with an ISA VGA card)
wrote:These are BIOS extension ROMs, and the motherboard BIOS will scan for these ROMs at startup, and execute their initialization ro […]
wrote:For the more technically informed on such shenanigans, will I always need to remove the BIOS chip for this or can I install a switch to connect/disconnect a handful of power/VCC pins?
These are BIOS extension ROMs, and the motherboard BIOS will scan for these ROMs at startup, and execute their initialization routine when found.
So you'll need to reboot the machine after you switch the BIOS on/off.
But I suppose it might work if you put a switch on some power pins, as long as you only switch when the machine is powered off.
When there's no power on the ROM, the motherboard BIOS will not detect the extension ROM, so the VGA BIOS won't initialize the card and install its int 10h handler.(I take it your Virge is a PCI card? That might explain why it works... I don't think it would work with an ISA VGA card)
Yeah, I was largely familiar with how the BIOS chips work on these cards, hence why I figured a simple power down (or in the brute force case, removing the chip) would do the job nicely. My next step is to test it with the power pins disabled and see what happens. The Virge/GX is a PCI card and a very compatible one to boot.
I spend my days fighting with clunky software so I can afford to spend my evenings fighting with clunky hardware.
wrote:I actually encountered a similar conundrum last week while trying to achieve better CGA support with an S3 Virge/GX. The palette wouldn't switch so Wizardry looked pretty bad. Obviously, running a CGA card alongside the VGA card doesn't work, but I did have an ATI CGA Wonder available. That card has a monchrome and CGA mode selector, as well as a CGA/monochrome monitor selector. So, running it in tandem with a VGA card I was able to run it as a Hercules card. I yanked the BIOS chip from the Virge, set the CGA Wonder to CGA mode, and voila, better CGA support.
If you are really adventurous you could try to create a hybrid BIOS for your use case and burn it into an EPROM.
wrote:For the more technically informed on such shenanigans, will I always need to remove the BIOS chip for this or can I install a switch to connect/disconnect a handful of power/VCC pins? Will that cause any issues with phantom power reaching the BIOS? Might I burn the apartment building to the ground?
I strongly advise against switching the power pins because of the voltage that will still be applied to the input pins. As a rule of thumb, that voltage should never exceed the supply voltage, which would then be 0V. Tapping into the chip enable line should be safe, though.
Back to topic:
There might be hybrid cards out there that allow you to switch the IO port addresses to MDA mode but can still be talked into outputting color, anyway.
This might be a long shot but the theoretical possibility is there.
