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Newbie with an XT - Options for displaying CGA

boggit

Experienced Member
Joined
Jan 4, 2024
Messages
180
Hello everyone!

I'm new to this community and, though I grew up with MS DOS and the x86 family, I have a limited knowledge about computer hardware (something I hope to correct with my new-found hobby).

I recently bought this beauty of a computer: an XT sans keyboard,floppy drive and hard drive. The only things included is the case, the motherboard (unsure if it is a 64-256 k board or a 256-640 k one, as I haven't received it yet) a floppy disk controller, a hard drive controller and a CGA card.

The 5143 monitor was available as a separate listing, but alas, I lost the bidding war for it. At the time, I figured I'd just use a VGA monitor with it, but it didn't take a whole lot of reading to realize that it is not that simple. I've published "want to buy"-posts in some relevant Facebook groups, but I'm not holding my breath. Also, I don't trust the postal service to deliver it in a working condition, so even if I found someone who had a 5143 for sale, I would have to travel to the seller to pick it up, and I lack both drivers license and car.

Thus, while waiting for my 40-ish pound parcel to arrive by mail, I've been scratching my head and looked through minuszerodegrees, these forums and other relevant places on the internet for guidance. From this information gathering, I have reached the conclusion that I have four different options for solving the display issue. Please help me by reading through the list of options below and telling me if I have understood the fact of the matter correctly or not.

1. Wait until I can get my hands on a proper CGA monitor.
Pros: * The historically correct option, ie the most "true" solution. * The 5143 looks great.
Cons: * Hard to find, might take years until I find someone willing to sell me such a monitor in working condition. * Will cost a shiteload of money even if I find someone willing to sell it to me. * Shipment challenge (as per the introductory text above).

2. Get a CGA digital to VGA analogue adapter and use a VGA to HDMI adapter so that I can use my existing LCD screen (something like this)
Pros: * I save space in my apartment. * I won't have to buy a new monitor.
Cons: * I might be forced to use a whole series of adapters, that all in all might cost €100-200, in order to get it to work. * I might not even find adapters with proper cases, so I'd have to 3D-print the housing myself in order for it to not look like absolute shite.

3. Switch out the CGA card for a VGA one.
Pros: * Makes it possible for me to use either my LCD monitor or a VGA CRT one. * Compatible cards seems to be readily available for not insane prices on Ebay. * Lets me use VGA and EGA modes in addition to CGA.
Cons: * Anachronistic setup. * Will probably not display true CGA mode but rather a crappy to half-decent CGA emulation unless I pay premium prices to get something like this.

QUESTION 1: I know that VGA mode will probably not run with any speed or agility on a 8088 system (unless the coders really knew what they were doing), but will VGA card in CGA mode be as fast as using a CGA card?

QUESTION 2: This card supposedly has "true" CGA emulation, with two ports. Will the true CGA emulation only be possible by using the CGA port on the card, ie with a CGA monitor?

4. Use a composite cable from the CGA composite port on the CGA card, connect it to this Tendak gadget, and use a HDMI cable from the Tendak to my LCD screen.
Pros: * I already own a Tendak gadget (works excellent for using an LCD monitor/TV with my Commodore 64) and a composite cable, so no pricey investments are required and I can use this solution as soon as I get my computer. * I can even use the extra artifact colors if I buy a cheap PAL to NTSC-adapter.
Cons: * The quality is almost guaranteed to be poor, with text being hard to read and so on. * Might not even display colors.


So, are these four options pretty much what I have to choose from, or am I missing something? Which alternative would you recommend?
 
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Hi and welcome to the site.

Having gone through a similar procedure, I would encourage you to read this thread (ignore the MDA in the title). It is actually my story about what I did with my CGA card in an XT clone. As you say, there are other important threads here and elsewhere.

A few other points/opinions I would mention.

I discarded trying to get a genuine legacy CGA monitor because a) they are much too expensive and you have the shipping expenses/dangers and b) I had concerns about how long a used one would last.

Your number 2 requires a little better understanding - at least it did for me. Many such devices in that heading will require some additional circuitry,

Know what signals your potential monitor will take - assume nothing unless you have the specs.

The 'BoginJr' circuit, including the recommendation to use RGB over the original G, works pretty well for me - but at some point, I just wanted some color.

CGA sucks if you are going to compare it to 'modern' video - just keep that in mind.

There are, apparently, VGA boards that will work with 8 bit isa. They are hard to find, but people track them, so do your homework and keep your eyes out for one. I never found one and got tired of "untested" syndrome.

Be very wary of cheap XXX to HDMI adapters. Do some homework there because I think that they are not as suitable as they sound.

There are a couple of boards that probably work well but are no longer available and/or are very hard to find. If you can't/don't want to build one yourself, get used to seeing that when you search.

The color device that I ended up with here works pretty darn well, at least for how I am using it. It works fine with my thrift-shop monitor using a HDMI to VGA converter and it works fine with my cheap, but modern flat screen HDMI. It is not cheap, but I am satisfied with it. Also, see the github story on that project in general because you may be able to build one yourself.

That's what I think anyways :)
 
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RGBtoHDMI.

One of these with the TTL board can handle CGA/EGA/MDA(Hercules) to HDMI.
That way you can play with more video cards/modes/computers without having to buy more adapters.
 
RGBtoHDMI.

One of these with the TTL board can handle CGA/EGA/MDA(Hercules) to HDMI.
That way you can play with more video cards/modes/computers without having to buy more adapters.
Thank you for your reply!

I looked into that gadget, but $120 plus shipping is a little steep for me, at least for something that does not really add new capacities to the computer besides letting me use my existing HDMI monitor for it. If I buy a VGA card for a third of the cost of the RGBtoHDMI, not only can I use a VGA monitor (or my LCD using ubiquitous VGA to HDMI adapters), but I can also run EGA and VGA modes (slow as that may be for a 8088 computer).

It is certainly worth considering, though, especially if I can use it to run smooth Amiga graphics on my LCD monitor in addition to the XT system.

  • What would you say are the main disadvantages for switching out the CGA card for a VGA card instead of buying the RGBtoHDMI?
  • Would I need anything more, apart from the RGBtoHDMI device itself, to connect my CGA card to a HDMI monitor?
 
If you have a TV with SCART or analog RGB input in general, you can also very cheaply build a CGA-to-RGB converter. You only need very few components to do so, mostly passives. The 5153 CGA display is also bascally just a gelded TV set.

This is one variant to do it:
 
Hi and welcome to the site.

Having gone through a similar procedure, I would encourage you to read this thread (ignore the MDA in the title). It is actually my story about what I did with my CGA card in an XT clone. As you say, there are other important threads here and elsewhere.

A few other points/opinions I would mention.

I discarded trying to get a genuine legacy CGA monitor because a) they are much too expensive and you have the shipping expenses/dangers and b) I had concerns about how long a used one would last.

Your number 2 requires a little better understanding - at least it did for me. Many such devices in that heading will require some additional circuitry,

Know what signals your potential monitor will take - assume nothing unless you have the specs.

The 'BoginJr' circuit, including the recommendation to use RGB over the original G, works pretty well for me - but at some point, I just wanted some color.

CGA sucks if you are going to compare it to 'modern' video - just keep that in mind.

There are, apparently, VGA boards that will work with 8 bit isa. They are hard to find, but people track them, so do your homework and keep your eyes out for one. I never found one and got tired of "untested" syndrome.

Be very wary of cheap XXX to HDMI adapters. Do some homework there because I think that they are not as suitable as they sound.

There are a couple of boards that probably work well but are no longer available and/or are very hard to find. If you can't/don't want to build one yourself, get used to seeing that when you search.

The color device that I ended up with here works pretty darn well, at least for how I am using it. It works fine with my thrift-shop monitor using a HDMI to VGA converter and it works fine with my cheap, but modern flat screen HDMI. It is not cheap, but I am satisfied with it. Also, see the github story on that project in general because you may be able to build one yourself.

That's what I think anyways :)

Thank you for your extensive and informative reply! I hadn't seen your thread before, and I will give it a full read-through.

Building my own boards would be quite a few bridges too far for me, at least at the moment, as I lack both space in my apartment and know-how when it comes to hardware in general and soldering stuff in particular.

I am leaning towards switching to a VGA card, as there are several ones where at least the main chip is listed among the 16 bit ISA cards that works on 8 bit ISA computers, and that are cheap enough ($30-40) that if I buy one and it doesn't work, it's not the end of the world.

I would like to know more about the disadvantages of that path, however, if anyone can fill me in.
 
If you have a TV with SCART or analog RGB input in general, you can also very cheaply build a CGA-to-RGB converter. You only need very few components to do so, mostly passives. The 5153 CGA display is also bascally just a gelded TV set.

This is one variant to do it:

Thanks! I really appreciate that you take your time to give me advice on this.

I might consider this if I can find pre-built CGA-to-SCART adapter or set to buy (preferably shipping from Europe), but I won't build any cards myself, at least not anytime soon.
 
4. Use a composite cable from the CGA composite port on the CGA card, connect it to this Tendak gadget, and use a HDMI cable from the Tendak to my LCD screen.
Pros: * I already own a Tendak gadget (works excellent for using an LCD monitor/TV with my Commodore 64) and a composite cable, so no pricey investments are required and I can use this solution as soon as I get my computer. * I can even use the extra artifact colors if I buy a cheap PAL to NTSC-adapter.
Cons: * The quality is almost guaranteed to be poor, with text being hard to read and so on. * Might not even display colors.

Does anyone have input/thoughts regarding this? I could just try it out as soon as my computer arrives, of course, but since it lacks both floppy drive and hard drive, I won't be able to fully test the graphics until I've bought proper peripherals.
 
Since you are in Europe, have a look at MCE2HDMI

and another implementation for SCART
 
Does anyone have input/thoughts regarding this? I could just try it out as soon as my computer arrives, of course, but since it lacks both floppy drive and hard drive, I won't be able to fully test the graphics until I've bought proper peripherals.

I got my computer today and, lo and behold, the composite -> Tendak -> HDMI solution actually worked right away!

The text looks much more blurry on this picture than what actually appeared on my screen. Still not sure if I'll only get monochrome or not, but this should be quite adequate until I can identify a more long-term solution.

Oh, and the POST codes indicate keyboard error, hard drive error and floppy drive error, all of which makes sense as I have none of those things yet.

IMG_7864.jpg
 
I don't suppose it would be possible to have both a CGA card and a VGA card slotted into the motherboard at the same time (maybe using BIOS or something to disable the one I don't want to use during startup)?
 
CGA and VGA cards conflict with each other. They cannot be disabled in software.
Some VGA cards can coexist with CGA, but will only operate in MDA/Hercules emulation mode, to avoid conflicting with the color text and graphics modes.
 
and another implementation for SCART

Could that device be used together with a SCART to VGA adapter (such as this one) to hook up my VGA monitor to the CGA card?

EDIT: This is the VGA monitor that I have, in case that makes any difference:

Skärmavbild 2024-02-05 kl. 12.38.41.png
 
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Could that device be used together with a SCART to VGA adapter (such as this one) to hook up my VGA monitor to the CGA card?

It looks like it will work, it's an active converter. In practice no one knows with these adapters, or what kind of picture you'll get.
Again, there is a better solution that is confirmed to work well. But I understand that the price might be deterrent.
 
Hi Boggit,

Just go for a VGA card. Most ISA Trident cards work fine on an XT. The have jumpers to force 8 bit mode; or autodetect mode.

Many games do run 'faster' in VGA mode than CGA mode. Incredible, but it is true. Probably because EGA/VGA mode doesn't need any graphic conversion to be displayed.

Also, Trident cards do have fine CGA compatibility too. There is nothing wrong with it.
 
dd
It looks like it will work, it's an active converter. In practice no one knows with these adapters, or what kind of picture you'll get.
Again, there is a better solution that is confirmed to work well. But I understand that the price might be deterrent.
Fair enough. Is the CGA2SCART PRO developer, Retro Erik, active on these forums?

Hi Boggit,

Just go for a VGA card. Most ISA Trident cards work fine on an XT. The have jumpers to force 8 bit mode; or autodetect mode.

Many games do run 'faster' in VGA mode than CGA mode. Incredible, but it is true. Probably because EGA/VGA mode doesn't need any graphic conversion to be displayed.

Also, Trident cards do have fine CGA compatibility too. There is nothing wrong with it.
Yeah, I'm using a Trident TVGA 8900C-based VGA card now that works well, with a perfectly decent CGA compability mode. I suppose it is just the idea of being True that pulls me towards running with a CGA card.
 
If you like soldering, take a look at this simple circuit I've made to connect a CGA card to a VGA monitor. It's very simple, but you'll need a 15kHz capable monitor or TV.
It changes the CGA palette to something I find more pleasing.



I tried a circuit like that on my RCA RT1970 and it did not work. The reason is not that it is a bad circuit, but that the monitor requires at least 31KHz in PC Input Mode. 15KHz is fine for Component Mode, but not for PC input mode. You are right to say...
...but you'll need a 15kHz capable monitor...
...but that capability needs to be at the VGA input. IOW my monitor is fine with NTSC composite, so it can do 15KHz, but not at the VGA input.

I bookmarked it somewhere, but a fellow has a circuit/device (I think it is pi pico based) that will output a few video modes that is especially useful to take with you to check out the thrift-store monitors to test. I should find that again as, IMO, flat screens that will work with retro video modes are not too easy to find.
 
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