VOGONS


First post, by RTLV_Design

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Hello all,

Im fairly new to the Vogons forums themselves but I have been very into the field of reverse engineering and have a bit of a proposal for you guys. I have had my hands on a few OG IBM CGA cards for a while, and am considering redesigning it for 1) my own 8088-Based PC/104 board, along with a potential MicroXT SBC concept I have been toying with. Is this something others would be interested in, or is this more of a personal pipedream? I would love to do my best to actually take the original CGA card and just compress it down as well, still in the ISA format. Feel free to let me know.

Regards,
Rob

Nothing helps the future more than respecting and learning from the past.

Reply 1 of 28, by Ozzuneoj

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Interesting idea. This may sound a bit redundant, but are you intending it to be connected to an actual CGA monitor?

I just ask because it seems like the cards themselves are still fairly common, where as the monitors are more scarce and harder to keep running, since they're all 30+ years old now.

Now for some blitting from the back buffer.

Reply 2 of 28, by RTLV_Design

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Ozzuneoj wrote on 2021-03-09, 06:39:

Interesting idea. This may sound a bit redundant, but are you intending it to be connected to an actual CGA monitor?

I just ask because it seems like the cards themselves are still fairly common, where as the monitors are more scarce and harder to keep running, since they're all 30+ years old now.

CGA Monitor Compatibility is definitely a must, but I would like to include either VGA or a digital converter so people can use it with modern display solutions, or standard CRT monitors. I am open to other options though!

Nothing helps the future more than respecting and learning from the past.

Reply 3 of 28, by Ozzuneoj

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RTLV_Design wrote on 2021-03-09, 06:47:
Ozzuneoj wrote on 2021-03-09, 06:39:

Interesting idea. This may sound a bit redundant, but are you intending it to be connected to an actual CGA monitor?

I just ask because it seems like the cards themselves are still fairly common, where as the monitors are more scarce and harder to keep running, since they're all 30+ years old now.

CGA Monitor Compatibility is definitely a must, but I would like to include either VGA or a digital converter so people can use it with modern display solutions, or standard CRT monitors. I am open to other options though!

I was actually going to suggest that. With compatibility for both, it sounds pretty neat. 😁

As mentioned, there are lots of cards out there that do CGA... but they are eventually going to get more scarce. A modern equivalent that isn't likely to blow a tantalum capacitor and take out someone's rare monitor (not sure if that actually happens) certainly has practical value in my book. 😁

Is EGA feasible? I'm sure that adds exponentially to the complexity of the card...

Now for some blitting from the back buffer.

Reply 4 of 28, by Tronix

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The author (@TubeTimeUS) of the SoundBlaster clone (SnarkBarker) is also doing a project to create a replica of the CGA card of FPGA... It's support VGA analog output for modern VGA monitors and TTL 5V output for vintage CGA or Mono monitors

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Reply 5 of 28, by Jo22

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Cool! Any chance of getting Composite CGA out of it?
That's the coolest part about CGA, IMHO! 😁

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 6 of 28, by debs3759

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Jo22 wrote on 2021-03-09, 08:59:

Cool! Any chance of getting Composite CGA out of it?
That's the coolest part about CGA, IMHO! 😁

I think you would need to consult the creator to ask that.

See my graphics card database at www.gpuzoo.com
Constantly being worked on. Feel free to message me with any corrections or details of cards you would like me to research and add.

Reply 7 of 28, by Benedikt

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Jo22 wrote on 2021-03-09, 08:59:

Cool! Any chance of getting Composite CGA out of it?
That's the coolest part about CGA, IMHO! 😁

What else would the footprint for the RCA jack be good for?

Reply 9 of 28, by rmay635703

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maxtherabbit wrote on 2021-03-09, 14:25:

out of all the early PC graphics standards, CGA is by far the least interesting IMO

CGA is Probably easiest to clone
but I would argue for a TGA2 video adapter which inherently supports CGA (and herc),

coupled with a Tandy sound card you wouldn’t need to hack the games ,as much

Reply 10 of 28, by Benedikt

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maxtherabbit wrote on 2021-03-09, 14:25:

out of all the early PC graphics standards, CGA is by far the least interesting IMO

But the easiest to implement, if we ignore MDA, which wasn't much of a graphics standard.
Besides, there was an abundance of mutually incompatible "super CGA" cards and solutions from the pre-EGA and early EGA era.
The most interesting ones are the PCJr. and Tandy graphics adapters, because they were so widely used.
A new card for Tandy graphics would basically allow people to turn arbitrary XT clones into machines that are mostly Tandy compatible.
Cards for Tandy sound already exist.

EDIT: Argh! I'm too slow.

Reply 12 of 28, by Benedikt

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This could be combined with all-modes-on-all-screens functionality similar to what the ATI Wonder cards provided, e.g. CGA in 16 shades of green on an MDA screen (via PWM ... I think), but additionally with support for VGA screens.
While the infamous "not invented here" syndrome affects us all, a cooperation would really make sense here.
In fact, I would have used the same ice40 FPGA that TubeTimeUS uses and I would have used it with very similar level shifting and DAC circuitry.

Reply 13 of 28, by RTLV_Design

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Apologies for the late reply, my alarms didnt go off this morning which is quite lovely.

In response to a few of these, lets get going.

1) If I were to go the FPGA route, I could probably integrate everything from CGA, EGA, Tandy, and VGA on one chip. I would need to look at how many logic cells would be necessary, but I don't see why that wouldn't be possible with an EPROM that can be cycled through to program the FPGA on boot. Something like a Cyclone 5 would be more than enough for any of these, or all of these at once.

2) I DO still want to do a chip-for-chip replica of the original CGA card, for nostalgia and for the sake of archiving the hardware.

3) I am very happy to cooperate with others, as I would love to make the best possible product for everyone 😀

Nothing helps the future more than respecting and learning from the past.

Reply 14 of 28, by Benedikt

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RTLV_Design wrote on 2021-03-09, 19:21:

2) I DO still want to do a chip-for-chip replica of the original CGA card, for nostalgia and for the sake of archiving the hardware.

3) I am very happy to cooperate with others, as I would love to make the best possible product for everyone 😀

In that case, you can find the CGA's (presumably) complete schematic diagrams in the appendix of its manual.
You can find an archived copy and further information on minuszerodegrees.
There is also the question of which original IBM CGA you want to clone, because the earlier model and the later model produce different colors on their composite output.

I do not think that cooperation between multiple people makes an awful lot of sense for a simple replica board layout with known schematics, but who knows. Maybe you will find someone.

Reply 15 of 28, by Jager

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RTLV_Design wrote on 2021-03-09, 19:21:
Apologies for the late reply, my alarms didnt go off this morning which is quite lovely. […]
Show full quote

Apologies for the late reply, my alarms didnt go off this morning which is quite lovely.

In response to a few of these, lets get going.

1) If I were to go the FPGA route, I could probably integrate everything from CGA, EGA, Tandy, and VGA on one chip. I would need to look at how many logic cells would be necessary, but I don't see why that wouldn't be possible with an EPROM that can be cycled through to program the FPGA on boot. Something like a Cyclone 5 would be more than enough for any of these, or all of these at once.

2) I DO still want to do a chip-for-chip replica of the original CGA card, for nostalgia and for the sake of archiving the hardware.

3) I am very happy to cooperate with others, as I would love to make the best possible product for everyone 😀

https://www.andavno.com/?cat=8 - chip-for-chip replica.
And my vote goes to cga/hercules/tandy/plantronics only, without ega & vga modes, since they'll need a bios extension.

Reply 16 of 28, by Benedikt

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I guess that makes another exact replica kind of pointless, unless you want to clone the other of the two versions.
+1 for a more versatile super-CGA card.
A CGA card with HGC+-style RAM font support would also be interesting. Or a HGC+ clone in general.

Reply 17 of 28, by RTLV_Design

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Jager wrote on 2021-03-09, 21:30:
RTLV_Design wrote on 2021-03-09, 19:21:
Apologies for the late reply, my alarms didnt go off this morning which is quite lovely. […]
Show full quote

Apologies for the late reply, my alarms didnt go off this morning which is quite lovely.

In response to a few of these, lets get going.

1) If I were to go the FPGA route, I could probably integrate everything from CGA, EGA, Tandy, and VGA on one chip. I would need to look at how many logic cells would be necessary, but I don't see why that wouldn't be possible with an EPROM that can be cycled through to program the FPGA on boot. Something like a Cyclone 5 would be more than enough for any of these, or all of these at once.

2) I DO still want to do a chip-for-chip replica of the original CGA card, for nostalgia and for the sake of archiving the hardware.

3) I am very happy to cooperate with others, as I would love to make the best possible product for everyone 😀

https://www.andavno.com/?cat=8 - chip-for-chip replica.
And my vote goes to cga/hercules/tandy/plantronics only, without ega & vga modes, since they'll need a bios extension.

As he seems to have dropped the project, or is not updating it further, this does still seem to leave a space in the market for a Chip-for-chip replica, along with proper released documentation of hardware functionality.

Nothing helps the future more than respecting and learning from the past.

Reply 18 of 28, by RTLV_Design

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Benedikt wrote on 2021-03-09, 21:22:
In that case, you can find the CGA's (presumably) complete schematic diagrams in the appendix of its manual. You can find an arc […]
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RTLV_Design wrote on 2021-03-09, 19:21:

2) I DO still want to do a chip-for-chip replica of the original CGA card, for nostalgia and for the sake of archiving the hardware.

3) I am very happy to cooperate with others, as I would love to make the best possible product for everyone 😀

In that case, you can find the CGA's (presumably) complete schematic diagrams in the appendix of its manual.
You can find an archived copy and further information on minuszerodegrees.
There is also the question of which original IBM CGA you want to clone, because the earlier model and the later model produce different colors on their composite output.

I do not think that cooperation between multiple people makes an awful lot of sense for a simple replica board layout with known schematics, but who knows. Maybe you will find someone.

I do believe that I have the first revision. Finding a part number on this is not exactly easy, but the silkscreened number at the rear of the board is 6278550A5048264032, with CG-94V0 and 941 on the rear.

Nothing helps the future more than respecting and learning from the past.

Reply 19 of 28, by Jo22

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Benedikt wrote on 2021-03-09, 22:22:

A CGA card with HGC+-style RAM font support would also be interesting. Or a HGC+ clone in general.

Interesting idea, since both CGA and HGC (aka MGA) are using the same CRTC and can co-exist, even.
They are like brothers, so to say. That's why I added a HGC clone in my XT class PC in first place, also.

The HGC clone card can be used as as a primary device (MODE MONO) or as a secondary device (MODE CO80).
HGC's graphics mode can also be used in Half-Mode (MSHERC.COM /HALF) without interferring with CGA's video memory.

Another interesting idea would be to implement Hercules InColor some day.
There's not much software support (MS Flight Sim, CompuShow2000 etc), but the hi-res graphics are maybe nicer than EGA. ^^

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//