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CGA Compatibility Tester vs. VGA cards

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First post, by 5u3

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Here is a table of test results conducted with the CGA Compatibility Tester on various VGA chipsets.

Generally, VGA cards emulate CGA well enough to be considered compatible, but some older games show graphical glitches or just plainly won't work with VGA cards. Some VGAs are better in emulating CGA as others, this table should help you to find one that works well with old games:

Chipset:                      Trident      W. Digital   Tseng        ATI           Cirrus Logic  generic    generic     DOSBox
TVGA8900C, WD90C30-LR ET4000AX VGA WonderXL GD510+520 VGA EGA [*] 0.74
TVGA9000i

Utility: SVM89.EXE VGAPLUS.EXE VMODE.COM VINSTALL.EXE DIP Switches none none machine=cga
v1.20 (TSR) v1.0 v2.0 set to CGA
-----------------------------------------------------------------------------------------------------------------------------------
Color Select Register
Border/Overscan: ok [1] ok fail ok ok fail fail fail
Med-Res. background: ok ok ok ok ok fail fail ok
Hi-Res. foreground: ok ok ok ok ok fail fail ok
Med-Res. palettes: ok ok fail [2] ok ok fail fail [7] ok
Textmode Manipulation
40-column display: ok ok ok ok ok ok ok ok
Hicolor backgrounds: ok ok ok ok ok fail fail [8] ok
Cursor control: fail [3] ok fail [3] ok ok fail fail fail [3]
8x8 font display: ok [4] ok [4] ok [4] ok [4] ok fail ok ok
M6845 Compatibility
Vertical retrace: ok fail ok fail fail [6] fail ok ok
Horizontal retrace: ok ok ok ok ok fail fail ok
Textmode row reprog: ok ok ok ok ok fail fail ok
Textmode row/col reprog: ok fail ok fail ok fail fail ok
Display positioning: ok fail ok fail ok fail fail fail
Start Address reprog: fail [5] ok fail [5] fail [5] ok fail [5] fail [5] ok
------------------------------------------------------------------------------------------------------------------------------------

[*] Results from ATI EGA Wonder 800 and Paradise PEGA 1A
[1] Only cycles through lower 8 colors
[2] Works except for cyan/red/white palettes
[3] Dual-line and strikethrough cursor missing
[4] Minor differences from IBM CGA font
[5] Corrupt/missing screens at end of vertical scroller
[6] Probably ok with 15 KHz CGA monitor
[7] Cyan/magenta/white palette only
[8] High-intensity colors only

[Edit 2011-09-20] Updated results: ATI VGA Wonder XL (tested by MaxWar)
[Edit 2011-10-01] Updated results: ATI EGA Wonder 800 and Paradise PEGA 1A (tested by DonutKing), Cirrus Logic GD510+520 (tested by Vlask)
[Edit 2012-01-11] Updated results: Cirrus Logic GD510+520 (tested by retro games 100)
[Edit 2012-01-12] Minor corrections: Cirrus Logic GD510+520, Tseng ET4000AX
[Edit 2012-02-01] Minor corrections: Cirrus Logic GD510+520 (tested by sprcorreia), added DOSBox results
[Edit 2015-06-30] Minor corrections: Added TVGA9000i

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Below is the text of my original post.
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Recently I stumbled upon Trixter's CGA Compatibility Tester, a program which tests CGA cards for compatibility issues and shows off some neat CGA register tricks.

This made me wonder: How good are VGA cards at emulating CGA?

After running the CGA Compatibility Tester on a couple of random VGA cards, it soon became apparent that they really suck at this: All cards failed the same tests in exactly the same manner. I didn't expect any VGA card to be 100% register-compatible with CGA, but these results were rather disappointing.

However, I remembered that some old ISA cards could be switched into a special CGA emulation mode by running an utility or setting some DIP switches. Further researching on the net and rummaging in my old hardware box scared up three such VGA cards, along with the utilities to activate their CGA emulation! 😀

The table above lists the test results for my cards in CGA emulation mode. The last column (generic VGA) represents the results without activating the CGA emulation.
Note that I left out some of the tests (Video RAM Speed Benchmarks, CGA "Snow" visibility, Monitor Calibration and Interlaced video mode) in order to keep things manageable.

So, is there a card capable of passing all these tests?
Let's find out: If you have a VGA card with better CGA compatibility than a generic VGA, please post your cgacomp test results here!

These are the utilities I used for the tests:

Attachments

  • Filename
    SVM89.EXE
    File size
    24.24 KiB
    Downloads
    966 downloads
    File comment
    SVM89.EXE v1.20 - video mode switching utility for Trident 8900 cards
    File license
    Fair use/fair dealing exception
  • Filename
    vgaplus.exe
    File size
    14.88 KiB
    Downloads
    849 downloads
    File comment
    VGAPLUS.EXE v1.0 - video mode switching utility for WD Paradise WD90C30 cards
    File license
    Fair use/fair dealing exception
  • Filename
    vmodetsg.zip
    File size
    9.72 KiB
    Downloads
    814 downloads
    File comment
    VMODE.COM v2.0 - video mode switching utility for Tseng ET4000 cards
    File license
    Fair use/fair dealing exception
Last edited by 5u3 on 2015-06-30, 09:04. Edited 8 times in total.

Reply 1 of 94, by retro games 100

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Good post! You may be interested in this webpage. It's a wiki vintage computer page about VGA backwards compatibility. The footnote area on this page is curious. It says that the Tseng ET4000 chipset has no compatibility mode. Perhaps this "plain vanilla" ET4000 differs from the AX variant?

Reply 5 of 94, by retro games 100

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IMHO, I think that having just one sticky at the top of Marvin called "the best of Marvin" thread is a worthy idea. If you have too many stickies at the top of Marvin, it pushes all new threads (however good they may be) down the page in to "second place". Inside the "best of Marvin" top sticky thread, you could have a summary and link to each of these great threads.

Reply 6 of 94, by 5u3

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Thanks for your comments! 😀

retro games 100 wrote:

Good post! You may be interested in this webpage. It's a wiki vintage computer page about VGA backwards compatibility. The footnote area on this page is curious. It says that the Tseng ET4000 chipset has no compatibility mode. Perhaps this "plain vanilla" ET4000 differs from the AX variant?

Yeah, I came across this wiki page too, the entry about ET4000 is probably just an oversight. Also, the compatibility mode doesn't work with all ET4000 cards. I've tried the VMODE.COM utility with a PCI ET4000/W32, and it doesn't offer the CGA compatibility mode as with the ISA ET4000AX.

h-a-l-9000 wrote:

Would also be interesting if the configuration program is a TSR. If it is it most likely uses the NMI to trap hardware accesses, which can mess up timing.

Good point, I haven't thought about that. Turns out that the SVM89.EXE utility for the Trident 8900 cards is indeed a TSR. I'll change the table accordingly.
This explains why the Trident doesn't stay in CGA compatibility mode during a reset, while the other two cards keep it up until power is cut or the emulation is switched back to VGA.

About making this thread sticky: I like RG100's idea about having a "best of" thread, as the thread listing is already becoming cluttered with stickied threads. Is there someone willing to manage a "best of" topic?

For those of you with a Trident 8900, WD Paradise 90C30 or Tseng ET4000, I've attached the utilities at the first post.

Reply 8 of 94, by VileR

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has someone been able to test this utility on an ATI VGA-Wonder?

curious about this one in particular, because it can drive a CGA (or mono) monitor too.

Reply 9 of 94, by MaxWar

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Funny that you talk about the VGA-wonder.

Im am restoring a 486 system and it has the VGA wonder XL in it.
When im done setting this all up, i could try the test with my card.

Reply 10 of 94, by 5u3

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MaxWar wrote:

Im am restoring a 486 system and it has the VGA wonder XL in it.
When im done setting this all up, i could try the test with my card.

Please do! 😉 We need more CGAcomp test results!

Reply 11 of 94, by MaxWar

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Ok, i managed to track down the original disk images for my ati vga wonder xl !
http://ibm-pc.org/manuals/other/ati/vgawonder/vgawonder.htm
I made the test after setting display mode to cga using the utility vinstall.exe and here are the results:

Color Select Register :
--all pass

Textmode Manipulation :
-- Cursor control fails, see no cursor at all. Its actually better in vga as only Dual-line and strikethrough cursor missing then*Edit : pass after tweak
-- 8x8 font display: ok , looks like the fat font but some minor differences on a few characters (apparently same result as other cards, no big deal)

M6845 Compatibility :
--Vertical retrace: fail , 70 hz instead of 60 hz. Im actualy happy about this as i hate 60hz. 60hz = can see the screen flashing, gives headaches and drives nuts. So this one fails at failing = win 😁
--Textmode row reprog: not sure about this one, It appears to do some row reprog but im not sure if it does it properly, looks a bit weird, i would say its fail until otherwise proved. *Edit : pass after tweak
--Textmode row/col reprog: fail : I do not get a garbled display like in vga but it does not reprogram text res.
--Display positioning: Fail, should i see the screen moving ?
--Start Address reprog: fail [5] ( vertical corrupt , horizontal ok)

*All the tests not mentioned are 100% pass.

I wonder if results would be different if i was using an actual CGA monitor, as this card does have a cga connector on it! Too bad i dont have one, i would gladly trade one of my VGA monitors for a CGA one 😜

Apparently the biggest issue with the emulation if i was to use it with actual cga games would likely be with text mode reprogramming. I think im gonna try to find one of the games mentioned in the compatibility tester and see how this performs in the field !

Edit: tried a few cga game that use text mode reprogramming and they are not displaying properly, all of them. Looking at you previous results, the trident card seem to be the best one. I also have a trident isa card i think. hmmm.

Last edited by MaxWar on 2011-09-20, 04:13. Edited 1 time in total.

Reply 12 of 94, by VileR

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nice!

can you tell if the vinstall.exe utility is a TSR (like the Trident's)?

[EDIT] - checked the manual from that link, seems like it's no TSR. Looks like this card has some fun options to play with (such as faking MDA/Hercules on any monitor in green, amber or grey) 😁

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Reply 13 of 94, by MaxWar

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Yes the card has cool features but it does not perform as well as i would have liked in the cga emulation 🙁 . Some more tests could be done such as trying with the two other versions of Vinstall, and also trying with cga monitor.
Also there is the fact that its arguably pointless to try to play cga games on this machine as my overdriven 486 usually plays cga games about one order of magnitude too fast, even with turbo at off.

Reply 14 of 94, by DonutKing

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Also there is the fact that its arguably pointless to try to play cga games on this machine as my overdriven 486 usually plays cga games about one order of magnitude too fast, even with turbo at off.

You can try this... ICE enables the L1 and L2 cache while ICD disables it. Requires a 486 processor.
http://dl.dropbox.com/u/9151127/icdice.zip
By using these in conjunction with the turbo switch you can *usually* get the games down to a playable speed.

If you are squeamish, don't prod the beach rubble.

Reply 15 of 94, by MaxWar

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I tried playing diggers, with turbo its only a screen blur. Without turbo you can see a bit whats going on, i tried to play it but at this speed its really hard. Would be a nice training for jedi apprentices.
Maybe ill try it without cache just for lulz, but id rather get my hand on a 286 😜

Reply 16 of 94, by VileR

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The best slowdown utility I remember trying is bremze, used to brake my old PII ultra smoothly down to down to XT speeds... but yeah, a 8088/286 rig would be far nicer for those.

best not to keep on derailing this thread, though 😁

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Reply 17 of 94, by MaxWar

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Returning to the subject, i was making a bit of research on a cirrus logic vlb board i have when i stumbled on this bit of information :
"CL-GD510 + 520 - ISA SVGA "Eagle II" chipset, known for 100% CGA emulation. (1988)"
from wiki, references:
http://books.google.com/books?id=kDoEAAAAMBAJ … 0cirrus&f=false
and
http://www.oldskool.org/guides/oldonnew/video

Looks like the CL-GD510/520 chipset might be a winner 😁
Anybody got one of those ??

Reply 18 of 94, by VileR

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Since Trixter wrote that guide in the 2nd link, as well as the test utility, perhaps he'd have the results for this card?

by the way, that page also seems to have info on fixing text-mode reprogramming games on the ATI VGA Wonder (see the info on grptxt.bat which uses vinstall) 😀
maybe you can try that and rerun that specific test on your ATI?

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Reply 19 of 94, by MaxWar

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My bad! You are totally right, i had not made the connection.
Then he says himself that the card is known for 100% cga compatibility, that probably means he tested it with his own tester?

He also writes about how to tweak Vinstall to get some cga games to display properly with the ati wonder! Maybe this ati still has some surprises to give? 😳

This topic makes me feel like im doing archeology, its pretty cool!

Edit : i tried the bat files with the vinstall commands in it and it fixes the textmode row reprogramming test as well as the cursor control test and makes the games mentioned in the exemple display properly! Really this is great. It is all written on the readme.gam file on the floppy but i overlooked it at first.

BTW Round 42 is a kickass invaders like game, i can see how cool it actually is now that it displays properly. 😁