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About using VGA monitor(HP 91) on XT (again).

J

JT64

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Oct 21, 2008
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Someone said that the VGA card in XT may not detect a color monitor and therefore switch to monochrome mode for the monitor.

Now i got another monitor a HP 91 monitor but still same problem remain, and i am thinking, is it really was a detection problem on the card, or could you just somehow switch mode with software.

Isn't there VESA drivers that is supposed to be able to set mode for the graphic card?

Or is there jumper settings for the CGA versus/and VGA that need to be set on the mothercard. Right now i can use both the CGA port on motherboard and the VGA card (but only one at a time).

When i attach the VGA monitor my CGA monitor only show a blinking marker, so i can not use both the CGA monitor and the VGA(MONO) at same time. But both are working without any jumper settings.
I am thinking maybe i must turn off CGA on motherboard to get color VGA, can that be it?

There is alot of jumper on mothercard unfortunatly i do not have the servicemanual. I guess they handle floppies,speed and ports, but maybe also onboard CGA on and off?

There is a MONOCHROME switch at back of computer when i use this none of the monitors sync, so that is not the problem for sure.

Is this really a problem for the VGA card related problem with the monitor, could it not be a jumper on the mothercard that have to change?

And if it is a VGA card monitor detection problem could you not fool it with software or a VESA driver mode?

Do i really have to cut a monitor wire or resolder?

JT
 
If I am understanding you, the CGA card is actually onboard?

If this is the case, then I am guessing there is a way to disable this. Is there a part number on the motherboard that you can google for a schematic?
 
Last edited:
Probably depends on the video card. What VGA card are you using ?

I had an ATI VGA Wonder that always came up in monochrome.
Finally figured out I had to run the setup program for the VGA card
to set this to color.
 
mikey99 said:
Probably depends on the video card. What VGA card are you using ?

I had an ATI VGA Wonder that always came up in monochrome.
Finally figured out I had to run the setup program for the VGA card
to set this to color.
Click to expand...

It is a WD90C11 based card with VGA bios and 512 KB ram.

See picture:
http://www.vintage-computer.com/vcforum/attachment.php?attachmentid=964&d=1226371124

I have tested all switches on card does not matter always monochrome mode, and using certain settings it do not work at all.

Maybe i should set the external CGA switch to monochrome, and try all switches on the VGA card again to see if any will get synch.

JT
 
lutiana said:
If I am understanding you, the CGA card is actually onboard?

If this is the case, then I am guessing there is a way to disable this. Is there a part number on the motherboard that you can google for a schematic?
Click to expand...

Yes the motherboard have 2 serial,1 parallell and a combined CGA and Monochrome port.

Here is a link about PC XTRA my XT have more memory though. It does not say that the CGA is on motherboard just what type of monitors supported in article.

http://www.atarimagazines.com/creative/v10n12/71_ITT_Xtra_an_IBM_PC_compa.php

JT
 
I am thinking that there is a way to disable the on board graphics. Probably via a jumper (or possibly a dip switch). If you can get the model of the motherboard you can most likely Google it for a list of all the jumper settings.
 
lutiana: I am thinking that there is a way to disable the on board graphics.
Click to expand...
I guess I didn't understand the OP then. :( I've only seen XTs which need a seperate adaptor for video. Those have a block of (8 iirc) dip swithces on the MB which need to be set for video and other things. Switches 5 and 6 are both set to on if you are using EGA/VGA. In case it actually is a regular XT, here are some more settings:

5 off, 6 off - MONO
5 on, 6 off - CGA 80x25
5 off, 6 on - CGA 40x25

You also need to set the other switches for coprosessor, floppy drives, and memory. I'm sure there are some XT experts here who can point to a page, otherwise I'll type out the whole list if it's needed.
 
I think (and I could be wrong on this) those settings are IBM specific, and none of those (once again I could be wrong here) have on board video.

It sounds like he has an HP system? With the correct model number we'd be better able to help.


Ole Juul said:
I guess I didn't understand the OP then. :( I've only seen XTs which need a seperate adaptor for video. Those have a block of (8 iirc) dip swithces on the MB which need to be set for video and other things. Switches 5 and 6 are both set to on if you are using EGA/VGA. In case it actually is a regular XT, here are some more settings:

5 off, 6 off - MONO
5 on, 6 off - CGA 80x25
5 off, 6 on - CGA 40x25

You also need to set the other switches for coprosessor, floppy drives, and memory. I'm sure there are some XT experts here who can point to a page, otherwise I'll type out the whole list if it's needed.
Click to expand...
 
I guess we'll just have to wait for JT64 to wake up! I suppose it's about 7 in the morning there. Let's hope he checks the net before breakfast, or at least before us pacifictimezonians go to bed. :)
 
lutiana said:
I am thinking that there is a way to disable the on board graphics. Probably via a jumper (or possibly a dip switch). If you can get the model of the motherboard you can most likely Google it for a list of all the jumper settings.
Click to expand...

I do not think the board is on the net at least not on stason, i googled alot for it.

But i looked closer on board there is actually three blocks of switches. Two blocks with 10 or 12 and one block with 4 or 5.

I probably could take out the motherboard but they really made a good job make it unreachable building a big bracket with housing over it holding floppies and AC so i am not over keen doing that. I basically would have to dismount every screw.

The switches are easy to reach though with a screwdriver, i just would need the manual, fiddling with 24 switches will turn out impossible.
I also got a 5.25 floppy drive that i mounted into it, but the board is probably set for one floppy. I interchanged the 3.25 and 5.25 floppy to see if the drive B: was detected(I have no 5.25 floppies), but it was not so this probably also motherboard setting.

There was one set of ITT PC XTRA manuals sold on E-bay last week, would be nice with a scan if someone here know who bought it.

JT
 
lutiana said:
I think (and I could be wrong on this) those settings are IBM specific, and none of those (once again I could be wrong here) have on board video.

It sounds like he has an HP system? With the correct model number we'd be better able to help.
Click to expand...

The board is an "ITT" model number 401470-02, , model is called PC-XTRA.

JT
 
I don't know why i did not check before, but i moved the card to a pentium 500 mhz modern computer with one 16-bit ISA slot.

Turns out the card and monitor works perfect together in fullcolor VGA mode, so either it is a switch on motherboard that need to be adjusted or the card fails to initialise properly because it is 16-bit in a 8-bit slot?

What do you think switch or 8-bit slot cause the Monochrome mode?

I think i am stuck without a manual 3 switch boxes with at least 22 switches is way to much to fiddle with by pure random test.

I also checked up the FCC-ID on graphic card, it is
1CUPVGA-GWV11 or more probably ICUVGA-GWV11 it does result null result at
http://www.fcc.gov/oet/ea/fccid/

JT
 
JT64 said:
I don't know why i did not check before, but i moved the card to a pentium 500 mhz modern computer with one 16-bit ISA slot.

Turns out the card and monitor works perfect together in fullcolor VGA mode, so either it is a switch on motherboard that need to be adjusted or the card fails to initialise properly because it is 16-bit in a 8-bit slot?

What do you think switch or 8-bit slot cause the Monochrome mode?

I think i am stuck without a manual 3 switch boxes with at least 22 switches is way to much to fiddle with by pure random test.
Click to expand...

Ok, what is the exact make and model of the computer your trying to run this in?

I doubt that 8 bit mode would drop it into monochrome, and I am thinking it may not be the switches on the card, but we need a clear picture of make and model of the computer itself to help you any further.

At least you know now that the VGA card does work.
 
lutiana said:
Ok, what is the exact make and model of the computer your trying to run this in?

I doubt that 8 bit mode would drop it into monochrome, and I am thinking it may not be the switches on the card, but we need a clear picture of make and model of the computer itself to help you any further.

At least you know now that the VGA card does work.
Click to expand...

I'm not sure what you mean by make, the brand is ITT XTRA/PROFESSIONAL SERIES and the "ITT model number is 401470-02".
i do not think this computer that common it has serial 001153.
I think that is as close i will get.

ITT no longer in buisness so i have no idea for where to look a manual.

There is possibly a FCC-ID at the motherboard, but this motherboard really well built in with brackets for AC and floppies.

The work to pick out motherboard is compared to dismantle and build chassi with motherboard on a Compaq. They really built things in well.

It has 640 KB + 128 KB extended, 2 serial, 1 parallell and one CGA/Monochrome port with switch on motherboard.
On motherboard it three switch blocks, 2 with 8 switches and one with 4 switches so it was "only 20 switches" but i feel that at least 16 to many.

I have a feeling my attached VGA will boot in color as soon i turn off the onboard CGA, but i am not sure. Could anything go wrong if i test the switches one and one?

JT
 
JT64 said:
I have a feeling my attached VGA will boot in color as soon i turn off the onboard CGA, but i am not sure. Could anything go wrong if i test the switches one and one?

JT
Click to expand...

Could this cause harm? I am honestly not sure. I am thinking not but as you cannot find any manuals on it (nor can I, but look here) a brute force attempt may not be too hard.

Perhaps post a picture (or pictures) of the motherboard and someone might recognize it.

If I were to guess I'd say that it would be the jumpers/dips switches closest to the CGA port that might do it.

Hope this helps.
 
The HP91 is a (nice) monitor; I've been using it on one of my systems for several years with various VGA-equipped machines with no problems at all. If JT wants, I'll try a VGA-equipped XT with it, but I don't expect any problems.
 
Chuck(G) said:
The HP91 is a (nice) monitor; I've been using it on one of my systems for several years with various VGA-equipped machines with no problems at all. If JT wants, I'll try a VGA-equipped XT with it, but I don't expect any problems.
Click to expand...

No i do not think that the problem is either the VGA card works fine in the pentium III, so i do not think it is related to monitor detection.

I suspect that the motherboard with onboard CGA somehow force the VGA board into monochrome mode. I guess i have some 20 switch trial and error experience in front of me, let us hope the old machine hold together for it.

JT
 
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