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CGA/EGA to VGA adapter

Marrr said:
Wait a min...
What exactly you need A/D conversion for? CGA/MDA/HGC/EGA all output TTL, so no need for A/D here.
Perhaps for CGA's Composite out? If so, it's not that necessary: standalone TV tuners with VGA-out and eg. RF-in, Composite-in, S-Video-in are easy to get and cheap.
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You didn't read his statement carefully:

andrew said:
Doing analog video is much more difficult problem
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Andrew was reacting to my statement about how the job got simpler than, say, legacy VGA because both the input and output signals could be kept digital.
 
Chuck(G) said:
Andrew was reacting to my statement about how the job got simpler than, say, legacy VGA because both the input and output signals could be kept digital.
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Ah, OK, so it was just theoretizing.
Come to think of it, a *complete* CGA->VGA solution should have a Composite input as well. But I'm definitely not going to insist on that, I will be absolutely happy with TTL->VGA in one box, and Composite->VGA in another.
 
Chuck(G) said:
We sold a couple hundred of the things, but our timing was exceedingly bad--minis sunsetted pretty fast and the demand for higher-resolution graphics displays such as EGA pretty much ended the venture. I still have one of the cards and am a little surprised that no others have turned up in the "What the heck is this?" department.
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Yeah, who would use a thing like that when EGA was already available and VGA was in the works?

I've never used SIMCGA even though I have a Hercules card, because I have it in my Pentium and it doesn't work on dual-display systems. The ghosting of the 5151 is neat on games that support Hercules natively (like Maniac Mansion).

By the way, if anyone ever read "DOS For Dummies", the author (this guy Dan Gookin) said that SIMCGA stinks and that you should either get a color monitor or go to your local arcade if you want to play games.

That wasn't very nice. I bet you'd like to throttle that guy for insulting a program you wrote.
 
Chuck(G) said:
Hi Andrew,

At this point, I'm not entirely convinced that any microprocessor is required at all--or that one would make the job any easier.

I think we could keep the design to PLCC and DIP, however.

Although the Propeller is a very cool chip, for the ultimate in doing the most with the least, there's a Russian fellow who's made a terminal that drives a VGA display (it looks to be limited by the internal RAM of the uC) using nothing more than an ATMega8!
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Hi Chuck! Thanks! That's impressive for an ATMega8! Cool!

What I am suggesting is to use a small microcontroller to keep it flexible for MDA/CGA/EGA if possible. I suppose you could use a CPLD in DIP/PLCC but wouldn't it be limited to a single frequency? I suppose you could use programming jumpers to tell it what sort of input to expect. I guess I am just thinking along the lines of what I am used to. I sounds a lot like a fast uC to me.

Of course, whatever you come up with is good with me. I'll design the PCB to whatever you want. Its just that using DIP/PLCC is what I am more familiar with and will be lower risk and easier to build, I think, compared to a SMT design.

Please let me know what you are thinking. I'll whip up a PCB prototype and we can toss ideas around. If its small enough we can make small prototypes to test the theory.

Thanks and have a nice day!

Andrew Lynch
 
Fallo said:
That wasn't very nice. I bet you'd like to throttle that guy for insulting a program you wrote.
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Hi! Anyone who does anything, ever, will take criticism from other people -- much of it pointless.

Believe me, its just background noise after a while.

Thanks and have a nice day!

Andrew Lynch
 
Fallo said:
By the way, if anyone ever read "DOS For Dummies", the author (this guy Dan Gookin) said that SIMCGA stinks and that you should either get a color monitor or go to your local arcade if you want to play games.

That wasn't very nice. I bet you'd like to throttle that guy for insulting a program you wrote.
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Nope, he's entitled to his opinion. I made a fair amount of cash licensing the program to little outfits like Electronic Arts and The Learning Company, so I'll console myself with that. A few other authors asked to include it with their books.

Let a thousand flowers bloom, I say. You've got to have thick skin in the publishing business.

In a way, he was right--a CGA with a color monitor does look best for color graphics, but that was a fair pile of cash back then (probably close to $750-1000 at the outset). By comparison, MGA cards and monitors were inexpensive but did a vastly superior job of displaying text.
 
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Hi Andrew,

One area that I expect a bit of trouble with is "expanded" EGA cards. For example, I've got a couple here that will do Mode 12H on a multisync monitor (640x480). That's almost VGA territory and things start getting pretty fast there.

I want to take a look at some LCD display synchronization circuitry to see how they derive their pixel clock from a variable sync rate. It might involve a uC; I'm just not sure.

We could always go with DIP switches or jumpers and let the user tell us what he's got, but that clearly won't work with the multiple mode EGA cards.

I don't know at this point; I'll have to do some research.
 
Chuck(G) said:
Let a thousand flowers bloom, I say. You've got to have thick skin in the publishing business.
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Well, the book did say it was "for dummies", didn't it? All the same, it was probably the most famous book about DOS ever made as well as the progenitor of a series of books on all kinds of subjects unrelated to computing. I did learn some interesting things in its sequel "More DOS for Dummies", like using PROMPT $P$G $A to put a space after the command prompt and make it look less crowded.

Chuck(G) said:
In a way, he was right--a CGA with a color monitor does look best for color graphics, but that was a fair pile of cash back then (probably close to $750-1000 at the outset). By comparison, MGA cards and monitors were inexpensive but did a vastly superior job of displaying text.
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This guy didn't really like CGA either, although I'll admit it's an acquired taste. To be fair though, he only said that it had low-resolution text (which it does) and didn't have any comments on the graphics. The popularity of Hercules was because you got graphics along with sharp monochrome text. Lotus 123 alone probably sold many Hercules cards, although it wasn't until 1985 or so that games started supporting it.
 
More help, Please!

More help, Please!

OK guys, I'm getting a little frustrated. I've tried a couple options for my display with no luck. Here is what I've tried. I bought one of those CGA to VGA converters off ebay (http://www.jammaboards.com/store/cga/ega/yuv-to-vga-converter-pcb-gbs-8220/prod_291.html). These things come with minmal instructions so I've done the best I can. From the CGA out of the video card I connected red, blue, green, ground, Hsync, and Vsync. The converter intermitently sees a signal and erratic garbage comes out on the screen. The GUI interface is usable on my monitor, so I know its not completly dead and at least some connections are correct.

I also have some 8bit/16bit VGA paradise cards. They came with documention and programs. The literature explains percisely how to operate in an 8bit pc/xt system. I have been unable to get my monitor to see a signal from these cards (tried both CRT and LCD). I have also set the switches on the XT MOBO correctly for VGA. I have multiple copies of this card, and have tried several slots, so I think I can rule out a bad card.

The only success I have is the CGA out in composite format works fine (from the CGA card). But this is not good enough for everything I want to do. Any help on fixing either of the two options I have explored above would be greatly appreciated. I am doing everything I can to avoid purchasing a CGA monitor.

Thanks again...
 
I figured out the problem with the cga to vga converter. The converter is looking for the Hsync and Vsync to be combined. I'm still having a small problem where the screen jumps a bit once in a while but otherwise it is wokring.
 
Here's a very simple circuit to generate combined sync if your converter requires it:

cga.gif


You could also do the same thing with a couple of diodes, a transistor and a resistor.
 
hargle said:
I'm up for anything! I wish we could go 1 step back and make a "perfect video card" for our machines. Something that outputted to a VGA monitor, but was either switchable between CGA/EGA/VGA on the fly, or was capable of being VGA, but accepting all the tricks that CGA used with proper compatibility and speed.

I'm really quite video dumb though, so I don't know if anything like this would even be possible, and it would probably require a serious amount of FPGA work to accomplish. Anyway, sorry for the topic drift.

--
I bet a majority of the users here were SIMCGA users. I used it to play Thexder 1 on my mono 5150 back in the early 90's! The ghosting on it was really quite trippy.
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Now i may be very ignorant because i really do not know anything about the subject, but would it not be easier make a DVI/HDMI card. Isn't it just about a circuit with memories and a chip with two clocks? At least for graphics, but textmode fonts was in hardware so maybe no good idea and of course scaling will be an issue.

Is the 8-bit ISA bus architecture able to receive both audio data and video data over same bus. What about bandwidth 8*6 Mhz is that enough transfer both vid and audio?

JT
 
The problem doesn't go away if you employ HDMI. You still would need to make an adapter that's hardware-compatible (on the PC side) with CGA/MGA and contains the logic to perform pixel doubling (HDMI only allows for pixel rates 24MHz and above).

Commodity support chips might be a problem--HDMI manufacturers pay a royalty on each device sold as well as a fairly hefty "setup" fee. (That's why Dell doesn't use HDMI on its monitors, but uses a royalty-free interface called DisplayPort).

All in all, engineering an HDMI card for the 8-bit ISA bus couldn't be made to even remotely break even. However, if you know of some supportive collector with very deep pockets, we could start talking about it... :)
 
Chuck(G) said:
The problem doesn't go away if you employ HDMI. You still would need to make an adapter that's hardware-compatible (on the PC side) with CGA/MGA and contains the logic to perform pixel doubling (HDMI only allows for pixel rates 24MHz and above).

Commodity support chips might be a problem--HDMI manufacturers pay a royalty on each device sold as well as a fairly hefty "setup" fee. (That's why Dell doesn't use HDMI on its monitors, but uses a royalty-free interface called DisplayPort).

All in all, engineering an HDMI card for the 8-bit ISA bus couldn't be made to even remotely break even. However, if you know of some supportive collector with very deep pockets, we could start talking about it... :)
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I probably have a very naive idea about what both older graphic and newer cards is and what they do, i thougt a PC XT in graphic mode, basically piped and wrote "pixel update" information to a memory matrix on the graphic card, and that this same memory also continously is read by some sort of DA that make alot of analogue stuff that totally escapes me. But it is probably alot more to it i understand by your comments.


How do computer memories deal with read/write can they be read one speed and written to in another speed. If not how is such things handled?

EDIT: Oh and another thing, the DOS textmodes VGA,CGA,EGA do they have fonts stored in the graphic card bios or how is this handled? What information does bios basically contain? I thought it just handled what graphic mode was set how to read out the memory bufferts?

I probably should read a book about XT hardware and one about ASSEMBLER for X86 could you recommend one, i'm really not interested in the analogue conversion but want to understand how graphic modes is set how graphic memory written and read from and howto. Where can i read about pixel doubling?

JT
 
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MODEL GBS 8200
CGA EGA YPbPr to VGA Converter

Note:
The high definition converter GBS-8200 it’s professional of game convert.Support all games(Amusement、Play station、Xbox、wii……)convert to CRT monitor 、LCD monitor 、PDP monitor…… Auto scan CGA EGA YUV signal, VGA outputs , output high resolution signal.

Features:
♦ Supports CGA EGA YUV signal input.
♦ Supports VGA output 640*480,800*600,1024*768,1360*768
♦ CGA/EGA signal auto scan(15K,24K,31K)
♦ YUV(YPbPr) signal auto scan(480i,576i,720i,1080i,480p,576p,720p,1080p)
♦ Chinese and English OSD.
♦ Supports position control & zoom control.
♦ True digital 24-bit A/D converter for true 16.7-million color conversion.
♦ Supports all VGA monitor (CRT、LCD、PDP、PROJECT……)

Specifications:

Power DC5V 2A +/- 0.5v P7 or P9
Input signal CGA/EGA 14.5-16.5K23.5-25.5K30.5-32.5K Auto scan P3 or P11 or P10
RGBHV 30.5-32.5K Auto scan P10 or P11
VGA 30.5-32.5K Auto scan P10 or P11
Ypbpr 480p,576p,720p,1080p Auto scan P2
Ycbcr 480i,576i,720i,1080i Auto scan P2
Output signal VGA 640*480,800*6001024*768,1360*768 P4 and P12
User control Input Switch, Image Zoom, Image Position,Output Resolution ,R\G\B gain adjust. Menu KeyR\G\B VR
Dimensions 115*105*20mm

More info: http://www.gbs100.com/69
 
i agree with the guys saying just get an 8-bit compatible VGA card. i simply cannot reccomend a diamond speedstar w/ tseng ET4000 chipset enough for older machines. they're quite fast. VGA modes are still going to be slow in an 8088 even with that, but at least the CPU won't be bottlenecked by slow VRAM that many other cards have. it's a 16-bit card but 8-bit compatible.

i've usually just got my 8088 machines plugged into an LCD monitor, and it looks great. now if only they accepted AT keyboard signals. that would make it so much easier to just use with my KVM switches.
 
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