XT build, need graphic/display advice

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XT build, need graphic/display advice

Postby lowlytech » 2018-5-16 @ 04:43

I have finally gotten the itch to try to find an IBM XT 8088 or clone locally and have a question on the display. I know CGA and EGA were common for this, but I have an ISA video card that has a 8/16bit jumper that I would hope to use to connect a VGA monitor. Will this have any negative impact over using a real EGA monitor since they are so expensive? I have heard that VGA is software compatible to EGA, but didn't know the pitfalls of not using EGA would be.
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Re: XT build, need graphic/display advice

Postby root42 » 2018-5-16 @ 07:05

For a start, the 16 bit VGA card is just fine. The compatibility with EGA is usually very high. I have an EGA card lying around, but since I have no EGA monitor and not yet the OSSC, I am not using it.

One other option is to build your own 8 bit VGA card. There is a project with PCB schematics, plus you have to order an old stock Trident 9000 IC and it involves a lot of soldering... ;) I am planning to do that if possible at one point, but right now it's not worth the money and time.

If I were you, I would be on the lookout for an 8 bit EGA or maybe VGA card plus save up on the OSSC scan converter. I tried out the cheaper ones, but they usually fail for the text resolutions.
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Re: XT build, need graphic/display advice

Postby VileRancour » 2018-5-16 @ 10:51

With VGA over EGA the only real issue may be the refresh rate. 200-line EGA modes are 60Hz (like CGA) but VGA will display them at 70Hz, so anything which depends on that for timing could have issues. Unlikely to be a real problem with most things, but good to keep in mind.

On the other hand... with 8088 games/software CGA support is more common than EGA; and VGA doesn't do CGA as well as it does EGA.
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Re: XT build, need graphic/display advice

Postby root42 » 2018-5-16 @ 11:25

I Would play older Lucasfilm and Sierra adventures on an XT rig. They do support EGA and occassionally VGA. There is quite a bit of overlap of games from around 1988-1991 that still support XTs and run EGA or VGA graphics. Performance will of course vary, and a 286 will be invariably faster...
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Re: XT build, need graphic/display advice

Postby lowlytech » 2018-5-16 @ 13:37

Thanks for the replies. I should mention I have a late model 286/12 system with VGA onboard (WDC video). So you think I should concentrate on CGA for my XT when I get it or would it still be worth to use this CL-GD5320 8/16 bit VGA card I already have? I guess that is considering I can even find a CGA monitor, as all my crt's I have are VGA. Granted I grew up with CGA monitors/monochrome, and I really don't have any deep love for them when compared to EGA from what I remember (never owned a system in the house til 94, so VGA was it, but messed with plenty of machines with the latter).
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Re: XT build, need graphic/display advice

Postby Jo22 » 2018-5-16 @ 14:51

VileRancour wrote:With VGA over EGA the only real issue may be the refresh rate. 200-line EGA modes are 60Hz (like CGA) but VGA will display them at 70Hz,
so anything which depends on that for timing could have issues. Unlikely to be a real problem with most things, but good to keep in mind.

I second that. IMHO, some EGA games were even made on VGA systems or with VGA in mind (I'm tinking of Commander Keen 4, EGATrek).
To me, and perhaps many others, EGA always had been a valid VGA mode rather than a superseded graphics standard.
Beeing the optimist I am, I believe that EGA as a mode had its prime when VGA appeared and actual EGA cards vanished from the market. :)

Also, with the exception of some details and the 60 vs 70HZ refresh rate difference, VGA is quite compatible to EGA.
The older ISA VGA cards usually have an EGA emulation mode for programs with auto-detection,
while the newer PCI VGA's at least kept the IRQ2/9 support.

That beeing said, there's nothing wrong preferring an actual EGA card and an oldschool monitor.
Even late 90's gems such as Gateway still supported EGA mode.
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Re: XT build, need graphic/display advice

Postby lowlytech » 2018-5-17 @ 04:05

Maybe I might ask this question a different way. I remember CGA to be awful... magenta, white, cyan, etc. Was a real CGA monitor and card different? Maybe I only experienced CGA on VGA systems and that is why I have such lackluster memories of it.
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Re: XT build, need graphic/display advice

Postby infiniteclouds » 2018-5-17 @ 06:57

If you've already got a 286 for VGA/EGA and you're now leaning towards a CGA XT machine I would recommend a Tandy 1000 or 1000SX. Both are 8088, 4.77mhz machines (the SX has a fast mode 7.16mhz and more expansion slots) and it isn't too hard to find ones sold with a monitor. This way you get your XT CGA machine with the added bonus of 16 colour TGA and 3-Voice music/extra sounds when a game supports it. Having never checked I just looked at the prices of EGA/CGA monitors on Ebay and I payed less money for my Tandy 1000SX and CM-11 than that last year even with shipping -- and that's without considering the price of a CGA/EGA card. Just make sure a keyboard is included or factor that into the price because they are not compatible with standard XT keyboards.

Especially if you're leaning towards just CGA this absolutely seems like the way to go.
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Re: XT build, need graphic/display advice

Postby reenigne » 2018-5-17 @ 07:39

lowlytech wrote:Maybe I might ask this question a different way. I remember CGA to be awful... magenta, white, cyan, etc. Was a real CGA monitor and card different? Maybe I only experienced CGA on VGA systems and that is why I have such lackluster memories of it.


CGA is (naturally) technically inferior to the graphics standards that came after it. But it was not bad for the time when it came out (1981) and superior to other home computers available at the time like the Apple II and the TRS-80. Games that used (modified) text modes or that were designed to be used with the composite output weren't limited to 4 colours, and even 4 colour games could look pretty nice if the graphics were made specifically for it rather than being automatically converted from EGA or VGA graphics (losing detail in the process). https://www.vogons.org/viewtopic.php?f=63&t=57720 has some examples (albeit non-contemporary) of how good CGA can look. As with poetry, sometimes the limitations make the art better than it would otherwise have been.

So I suppose it depends on what your aim is. If you want a "historically accurate" system then an XT should be paired with CGA or MDA (or both). EGA was really more contemporary with the AT than with the XT (though did find some use as an upgrade that could use existing CGA monitors). If your aim is to display as many games as possible "how they were meant to look" then by all means go for VGA (although be aware that many VGA games will run too slowly on an XT).
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Re: XT build, need graphic/display advice

Postby tayyare » 2018-5-17 @ 09:39

I don't know the CGA card prices, I never intended to have one really, but what I have is an Oak VGA with 8/16 bit operation (auto detect), hardware switches for CGA, EGA, MDA modes. and two sockets for monitör connection (15 pin VGA and 9 pin TTL for CGA/MDA/EGA). Oak VGA cards was not being respected much and were going for very low prices, so it could be also an option.

This is exactly what I have:

https://www.classiccomputershop.eu/Webwinkel-Product-235194352/OAK-OTI067-VGA-EGA-combo-graphics-video-16-bit-ISA-PC-card-adapter-DOS-Windows-3.x-286-386-90s.html
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Re: XT build, need graphic/display advice

Postby lowlytech » 2018-5-17 @ 14:32

I like the idea of the Tandy, and honestly when talking to people around my area they were more popular than IBM XT systems as far as ownership. About 3 weeks ago I talked to a customer and they said they hauled their tandy 1000 to the dump 6 months earlier.
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Re: XT build, need graphic/display advice

Postby BloodyCactus » 2018-5-17 @ 16:01

Unless you have a dedicated CGA or EGA monitor, I'd just go with VGA and use a 2port KVM with your 286 so you can share 1 monitor.
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