• Please review our updated Terms and Rules here

CGA graphics on a monochrome ttl monitor

Q

QuantumII

Veteran Member
Joined
Aug 12, 2008
Messages
503
Location
Oslo,Norway
Hi all,

What's the different options I have to accomplish this ?

I've got a card wich has switchable MDA/CGA on it (Thanks Terry :) ) , but I cannot get anything else that monochrome graphics on it. Switching it to CGA (before I power on the PC) only gives a blinking cursor in the upper left corner. When I switch it to MDA it works as a monochrome adapter.

And no, replacing the monitor is not possible, as it's the built-in monitor in the Philips we're talking about. (It connects to the graphics board with a standard 9-pin TTL connector, like a regular monitor.
 
QuantumII said:
Hi all,

What's the different options I have to accomplish this ?

I've got a card wich has switchable MDA/CGA on it (Thanks Terry :) ) , but I cannot get anything else that monochrome graphics on it. Switching it to CGA (before I power on the PC) only gives a blinking cursor in the upper left corner. When I switch it to MDA it works as a monochrome adapter.

And no, replacing the monitor is not possible, as it's the built-in monitor in the Philips we're talking about. (It connects to the graphics board with a standard 9-pin TTL connector, like a regular monitor.
Click to expand...

Here's what's going on. When you set the card to CGA, it writes all the video data to B800:0. Since nothing is being written to B000:0, you get a blank screen on the monochrome monitor. I would take it that this video card has only one connection for a monitor, correct? If so, you would have to disconnect the monochrome monitor and use a RGB display to get the CGA output, and you couldn't use both at the same time.

Otherwise, the only way you can use CGA graphics on the monochrome display is with SIMCGA. That's assuming the card is a Hercules clone and not an MDA clone.
 
Have you looked up the MODE command to select the active display for DOS?
 
I take it that you can get monochrome text, just not monochrome graphics.

If that's the case, I suspect that the card can do CGA and MDA, but not CGA and MGA (aka "Hercules" graphics). Even SIMCGA is out of the question in that case.

Your choices would seem to be using either a real Hercules-type MGA card and the monochrome monitor or a CGA monitor on the card you've got (in CGA mode).
 
What kind of card is it anyway? If it's just "switchable" then you'd probably need a CGA monitor unless it can do Herc graphics. If it's something like the ATI cards, then you can emulate various modes on the same monitor. And of course there were also dual mode mono TTL/CGA monitors, but they're hard to find.
 
Have you remembered to ajust the swiches on the MB?

As I've understood, your computer is your XT, and it has the video settings of what the BIOS is going to use on the motherboard (SW1, nr 5 & 6). If you forget to change them from MDA to CGA, the BIOS will try to display stuff in the monocrome memory range, while the adapter tries to display from the CGA range.

I can tell that it does display CGA on an MDA because of he was able to see the blinking cursor.

*Edit*
I really don't know how to set the Philips BIOS to CGA mode. If you tried on your XT, it would be fine (see above). Is there some swiches on the Philips MB?
 
Last edited:
per said:
Have you remembered to ajust the swiches on the MB?
Click to expand...

Yes, at least according to the XT DIP switch settings. I have no documentation for the motheboard, so it's just guessing (Sw 5 & 6 on the 1st DIP bank) They make no difference..

Regarding replacing the monitor.. It's a built-in CRT which I cannot replace. Maybe hercules is the way to go then ?
 
QuantumII said:
Yes, at least according to the XT DIP switch settings. I have no documentation for the motheboard, so it's just guessing (Sw 5 & 6 on the 1st DIP bank) They make no difference..

Regarding replacing the monitor.. It's a built-in CRT which I cannot replace. Maybe hercules is the way to go then ?
Click to expand...

Try to use the card in the IBM XT, and use the monitor in the Philips. I assume you got a long enough cable.

When you got i connected, turn both units on at the same time. The philips should make some noises indicated that no videocard was found, and the monitor should display what's going on in the IBM XT.

If your card tried to output to an RGBI monitor, you would have gotten nothing on the display and maybe a fried monitor, not even a blinking cursor, as of the RGBI uses another pinout than the Monochrome monitor, so your card is capable of displaying CGA stuff to Monochrome monitors.
 
Last edited:
per said:
Try to use the card in the IBM XT, and use the monitor in the Philips. I assume you got a long enough cable.

When you got i connected, turn both units on at the same time. The philips should make some noises indicated that no videocard was found, and the monitor should display what's going on in the IBM XT.

If your card tried to output to an RGBI monitor, you would have gotten nothing on the display and maybe a fried monitor, not even a blinking cursor, as of the RGBI uses another pinout than the Monochrome monitor, so your card is capable of displaying CGA stuff to Monochrome monitors.
Click to expand...

Yes, that might be a nice experiment. The cable is very short (5 cm) but if I place the units very very close to each other , it should work :)
 
QuantumII said:
Yes, that might be a nice experiment. The cable is very short (5 cm) but if I place the units very very close to each other , it should work :)
Click to expand...

Ok, I tried this now! It works fine.

By the way. CGA performance was WAY better than with a VGA card in CGA mode..

And now the great news:

The Philips now can dispay CGA graphics. I was just flipping the DIP switches at random, one at the time, and found the two controlling the graphics.

It's bank 1, sw 3 and 4 (not 5 and 6 like on an XT).


Mission accomplished. Thanks all

cgaonttl_s.jpg
 
Last edited:
QuantumII said:
Ok, I tried this now! It works fine.

By the way. CGA performance was WAY better than with a VGA card in CGA mode..

And now the great news:

The Philips now can dispay CGA graphics. I was just flipping the DIP switches at random, one at the time, and found the two controlling the graphics.

It's bank 1, sw 3 and 4 (not 5 and 6 like on an XT).


Mission accomplished. Thanks all

cgaonttl_s.jpg
Click to expand...

Nice that yo got it working.

BTW, what card is it?
I got a similar card (I agree, it is totally superb).

If it is the ATI Graphics Solution, I can provide a driver for it (needed for Hercules graphics or if you want to change to other modes like 132*25 or 132*44 textmode).
 
QuantumII said:
It only says CGA_CARD..No info on manufacturer.. I think it's a generic CGA card clone.
Click to expand...

Can you provide a picture (not nessecary, a Chipset number and ammount of RAM, and nr. of swiches/oupouts will do just as good)?

It problably only got CGA and MDA then. Maybe Hercules, however, I really doubt that it got 640*200 in 16 coulors and 132 columns texmodes...

But that's what we got EGA and VGA cards for :)
 
per said:
Can you provide a picture (not nessecary, a Chipset number and ammount of RAM, and nr. of swiches/oupouts will do just as good)?

It problably only got CGA and MDA then. Maybe Hercules, however, I really doubt that it got 640*200 in 16 coulors and 132 columns texmodes...

But that's what we got EGA and VGA cards for :)
Click to expand...

Yeah, I can take a picture of later and post it here.
 
Nope, CGA-on-TTL Mono, or straight MGA. Nothin' fancy. No Herc emulation, ATI Graphics, etc...just a no-name whitebox thinggy.

The monitor in your Phillips might be a monochrome CGA-compatible that may not be capable of displaying MGA rez, etc.

--T
 
Last edited:
Terry Yager said:
The monitor in your Phillips might be a monochrome CGA-compatible that may not be capable of displaying MGA rez, etc.

--T
Click to expand...

I thought the situation was sorted (problem: Motherboard swiches)...

It is rather fancy how a program can display 16 shades of gray on a monitor only supporting 3 (signal off, intensity high doesn't really count since it is the same as signal off normal intensity).
 
Terry Yager said:
Nope, CGA-on-TTL Mono, or straight MGA. Nothin' fancy. No Herc emulation, ATI Graphics, etc...just a no-name whitebox thinggy.

The monitor in your Phillips might be a monochrome CGA-compatible that may not be capable of displaying MGA rez, etc.

--T
Click to expand...

After I figured out the Motherboard's DIP switches, I can confirm that all modes work.

MDA, CGA 80, CGA 40. :)

The monitor is not working with native CGA, it needs a cga-on-ttl card to work.
 
per said:
I thought the situation was sorted (problem: Motherboard swiches)...

It is rather fancy how a program can display 16 shades of gray on a monitor only supporting 3 (signal off, intensity high doesn't really count since it is the same as signal off normal intensity).
Click to expand...

Yes it works. Man you're quick! You posted this while I was writing the above post confirming that all modes work.
 
QuantumII said:
Yes it works. Man you're quick! You posted this while I was writing the above post confirming that all modes work.
Click to expand...

last class ended right before, so I was just checking for new posts right then. I can't talk much now; gonna catch the bus ;) .
 
You must log in or register to reply here.
Back
Top