Hercules graphics card question

[QuantumII]

Hi

Will a Hercules graphics adapter be able to output CGA-emulated graphics onto a monochrome amber monitor (Which is currently connected to a MDA card) ?

My understanding is that it can, but I'm not sure I am willing to go trough the hassle of getting a card just to find out it won't work...

 

[Terry Yager]

My (unreliable?) recollection is that the Herc doesn't support CGA natively, but there were programs available to make it do so. If you find that you cannot use the Hercules card, I have a switchable CGA/MDA card here that does CGA emulation on a TTL mono display. Holla if you need it.

--T

 

[QuantumII]

My (unreliable?) recollection is that the Herc doesn't support CGA natively, but there were programs available to make it do so. If you find that you cannot use the Hercules card, I have a switchable CGA/MDA card here that does CGA emulation on a TTL mono display. Holla if you need it.

--T

Hi

Yes, that would be nice. How much do you want for it ?

I plan to use it in my Philips luggable with an integrated mono amber display you see

PM also sent.

 

[tezza]

Hi

Will a Hercules graphics adapter be able to output CGA-emulated graphics onto a monochrome amber monitor (Which is currently connected to a MDA card) ?

My understanding is that it can, but I'm not sure I am willing to go trough the hassle of getting a card just to find out it won't work...

Yes, it can but you need software. In the day I used to play CGA games on my hercules-enabled home PC using this technique. It was a small auxillary program you ran first before running the CGA application. I think it was called "cga.com"?

I think I still have it somewhere.

Tez

 

[Micom 2000]

Yes. I have an old "Buttonware" type floppy which I picked up in the late 80s titled "CGA Emulation Utilities" which was put out by a company called Athena Digital. Their flagship program was called "Athena BIOS", and dealt more extensively with display problems. The freeware disk has a bunch of individual programs dealng with this including:

distype.com
HGCIBM.com
HGCTEST.bas
SIMCGA.com
CGA.com
and a few others including some patches for specific games, and .doc's for each program.

Unfortunately the 5 1/4 FDD on the only computer I have set up for the I-net is not functioning so I can't send you an image of it, without a lot of sneaker-netting and repair. I have been so dismally unsuccessful lately at repair, I have been avoiding it in order to thwart for a while my burn-out and falling lack of confidence.

You might be able to find these programs in some of the DOS archives and possibly even hit the jackpot if Athena has released their BIOS program to the public domain.

Lawrence

 

[tezza]

Ah, I'm pretty sure the one I used to use was SIMCGA.COM now I think of it.

I'll have a look for those programs tonight.

Tez

 

[Chuck(G)]

Ah, I'm pretty sure the one I used to use was SIMCGA.COM now I think of it.

I'll have a look for those programs tonight.

Tez

I have SIMCGA patches for some of the classic games that need a little help.

In some cases, the simulated graphics look better (i.e. finer resolution) than the CGA version; in some, the lack of color really is a problem.

The Herc Graphics Plus card had a loadable font memory that allowed some pretty cool effects (character codes were 12 bit in that mode, rather than 8).

Another thing to look for is the Herc InColor card, that gave Hercules compatibility but also supported color. I don't know if it supported a CGA emulation mode or not.

 

[QuantumII]

Thank you all. If some of you manage to dig up some of the utils, it would be very nice indeed

 

[Trixter]

I have SIMCGA patches for some of the classic games that need a little help.

In some cases, the simulated graphics look better (i.e. finer resolution) than the CGA version; in some, the lack of color really is a problem.

Wait a second -- I thought SIMCGA worked by copying b800 to b000 on a timer interrupt. In other words, the CGA data was not touched, just copied over to a visible viewport. If that's the case, then how could patches to a game make the graphics a finer resolution?

 

[MikeS]

Wait a second -- I thought SIMCGA worked by copying b800 to b000 on a timer interrupt. In other words, the CGA data was not touched, just copied over to a visible viewport. If that's the case, then how could patches to a game make the graphics a finer resolution?

----------
Wouldn't the higher memory, resolution, dot pitch, scan rate, lack of convergence issues etc. of the Mono monitor and adapter make a difference? I certainly seem to recall CGA emulated on an MGA combo being much cleaner and crisper than on a CGA combo.

I'd think the finer resolution is a given, but patches were needed by some CGA games etc. in order to run at all on a herc compatible.

 

[Chuck(G)]

Wait a second -- I thought SIMCGA worked by copying b800 to b000 on a timer interrupt. In other words, the CGA data was not touched, just copied over to a visible viewport. If that's the case, then how could patches to a game make the graphics a finer resolution?

Sorry, I wasn't being very clear--it's the display, more precisely, the row spacing that's finer. Another thing that seems to make a difference is that CGA used colored pixels; SIMCGA naturally uses dithered monochrome, so it looks smoother.

I'll have to check some old DC600 backup tapes for the last SIMCGA I worked on, but I'll get it dug out. I honestly never thought the subject would surface again...

 

[Chuck(G)]

I dug around a bit; here's SIMCGA 4.2E from late 1989. It's not the last version--that's on a DC1000 tape somewhere. I can dig it up if anyone's really interested. The attached file also doesn't have the patches and patcher for some games.

If anyone's interested in the later stuff and/or the patches, let me know and I'll go after them. All I have to do is learn to use Irwin EZTAPE all over again...

 

[Trixter]

Thanks very much for digging this out; I always wondered what technique you used, and now I know:

The trick used here is to program the HGC to display more lines of 3
lines per character time instead of 4 (The CGA displays 2). A service
routine hooked into the hardware timer interrupt (int 8) copies one line
to the third displayed line to give a filled-out image.

For mine, I reprogrammed the monitor frequencies so copying memory wasn't needed. This was obviously risky (monitor go poof!) and non-portable, which is why I never distributed my work.

Not to jump on you for 20-yr-old documentation, but one thing struck me:

All-in-all, the image looks superior to that obtained with the CGA.

I disagree. Just because something is reformatted and repositioned doesn't mean it looks better. If that were the case, I could toggle the "B&W" bit of CGA to run all 320x200 games in 640x200 "monochrome" and they'd look "superior".

 

[Chuck(G)]

For mine, I reprogrammed the monitor frequencies so copying memory wasn't needed. This was obviously risky (monitor go poof!) and non-portable, which is why I never distributed my work.

I tried doing that, but after a couple of fried flyback transformers, decided that it wasn't practical at all.

What I really wanted to do was used the DMA controller to do automatic block copying, but the *(^&% PC did a half-baked job of interfacing the DMA controller, so memory-to-memory copy using DMA isn't possible.

I disagree. Just because something is reformatted and repositioned doesn't mean it looks better. If that were the case, I could toggle the "B&W" bit of CGA to run all 320x200 games in 640x200 "monochrome" and they'd look "superior".

Yes, but you're getting half again as many lines on the screen. There is a visual effect.

As an example of something similar many late NTSC TVs "de-interlace" the video signal and display each non-interlaced frame twice. The claim is made for better resolution, even though neither the frame rate nor the bandwidth has changed.

By the same token, displaying your 320x200 CGA screen on a 640x480 VGA screen, doubling up pixels really does look better than native CGA display.

Or so it seems to me. I despised the CGA for its lousy resolution. 80x25 text to my princess-and-the-pea visual sensitivities is downright unreadable. I wouldn't even consider it then I bought my 5150, even though the sales guy offered me one heckuva deal. I bought an MDA and then moved to Herc when I needed graphics.

To this day, old graphics software still looks good on Herc and terrible on CGA.

 

[MikeS]

<snip>
To this day, old graphics software still looks good on Herc and terrible on CGA.

----
Amen! I don't get Trixter's point at all; we're talking about a higher resolution monitor here, not just changing resolution on a CGA monitor with its coarser multiple dots per pixel.

 

[Chuck(G)]

----
Amen! I don't get Trixter's point at all; we're talking about a higher resolution monitor here, not just changing resolution on a CGA monitor with its coarser multiple dots per pixel.

Another advantage of Herc is that a program doesn't have to wait for the retrace interval to update the screen when hi-res characters or graphics are being used. Makes for snappier displays, even on an XT.

The schematic capture program I started out using on a 5150, Schema, was horrible on CGA, but very good on Herc.

 

[Trixter]

What I really wanted to do was used the DMA controller to do automatic block copying, but the *(^&% PC did a half-baked job of interfacing the DMA controller, so memory-to-memory copy using DMA isn't possible.

Actually, it is possible, but only from system memory to system memory, and only using DMA channels 0 and 1. You have to copy at least 256 bytes since it is your copy that is refreshing the memory and 256 is the minimum needed to keep it alive. Some motherboard arrangements also require you to read from every bank or other irritation. A shame, since it would have been cool to get faster copies than the CPU is capable of.

By the same token, displaying your 320x200 CGA screen on a 640x480 VGA screen, doubling up pixels really does look better than native CGA display.

No, it honestly doesn't, for at least two reasons: 1. 200 lines does not map cleanly into 480 (some lines double), and 2. the 320x200 graphics were usually composed specifically for that mode and output device. Any color/brightness choices had the 200-line display in mind.

#2 isn't specific to CGA -- a lot of arcade machine emulations get this wrong too. Things don't look "right" if the resolution and mode don't match up. Progressive and/or line-doubled displays are nice, but they're not the right choice if your source wasn't composed for them.

To this day, old graphics software still looks good on Herc and terrible on CGA.

I submit you never had a decent CGA monitor The 5153 is pretty good. The PCjr monitor is terrible (color and brightness are great but the dot pitch is so bad that everything looks fuzzy). My first CGA was actually the 25Khz 400-line AT&T 6300 monitor, so I was spoiled rotten. I currently code on a 5153 and I'm very happy with it.

One of these days I'm going to finish my tweaked CGA graphics viewer. 40+ colors at a resolution of 80x100 already works on RGB; I hope to figure out how to use the same principles and tricks via the composite output to get even more.

 

[Trixter]

----
Amen! I don't get Trixter's point at all; we're talking about a higher resolution monitor here, not just changing resolution on a CGA monitor with its coarser multiple dots per pixel.

No, actually, that is what Chuck was saying -- that the same 320x200 graphics data looks better in B&W on a herc monitor.

If Chuck was saying that 720x348 Herc graphics look better than 640x200 CGA graphics, I would completely agree. But that's not what he was saying.

 

[Trixter]

Another advantage of Herc is that a program doesn't have to wait for the retrace interval to update the screen when hi-res characters or graphics are being used.

You only have to wait for snow on 1. IBM or AT&T CGA cards (most clone cards have dual-ported DRAM), and 2. only in 80-column mode. All other modes don't have the snow issue.

 

[MikeS]

No, actually, that is what Chuck was saying -- that the same 320x200 graphics data looks better in B&W on a herc monitor.

If Chuck was saying that 720x348 Herc graphics look better than 640x200 CGA graphics, I would completely agree. But that's not what he was saying.

--------
Duh, yes, I think it goes without saying that 720x348 might be sharper than 640x200, assuming that we're also comparing a TTL monitor to a CGA.

But I have to agree with Chuck, and it makes sense to me that the higher scan rate, the finer dot pitch, and the fact that you don't have to converge the three colours on a mono TTL monitor would give a good emulation utility better control and definition of the pixels on screen. But I guess it's subjective.

I've got a monitor that does both TTL and mono CGA; might be interesting to compare the real mono CGA to the emulation on the same monitor.