Retro Review: Octek EVGA-16 Part 3

20th November 2023

In Part 2 I ran some games and took some benchmarks of this VGA card from 1991.

In this final Part 3, we'll take a look at the Octek's emulation modes that support the MDA, Hercules and EGA standards. This is important if you use a VGA card like this to play old CGA or EGA games, as many of these games exploited certain characteristics of a true CGA or EGA card, which many chipsets that provide only emulation fail to do well.

Bear in mind that this is only emulation - the card does not have hardware present that directly mimics a Hercules, CGA or EGA card like some other VGA cards do. It does not have a 9-pin TTL output for display on a digital monitor, so there is still digital-to-analog conversion taking place to output to a VGA monitor. The compatibility of this emulation can vary from chipset to chipset, so we'll see how the Chips & Technologies F82C451 fares in these other modes.

To change the emulation mode, Octek provide the SETVGA.EXE utility, as we saw in Part 1.

EGA Compatibility

Ignore the "AGP 2x bus" detected - I'm running this on a PC Chips motherboard that has an embedded AGP video card,
and you cannot disable it so it's confusing software!

4D Sports Driving (Stunts) did ok during a race, but on the replay it showed a ton of graphical glitches with the redraw. The same thing occurred when running out of emulation mode, but with the game set to EGA.

Prince of Persia ran well in EGA emulation mode, and this is a game that's very well-suited to EGA - you can hardly tell the difference between VGA and EGA.

Sim City ran well in EGA emulation mode - I believe it's the best graphics standard the game supported.

 

CGA Compatibility

Now to check what the card appears to be when running in CGA Emulation mode:

All good here...

In emulation mode, diagnostic software does seem to be identifying the presence of a legitimate CGA card.

4D Sports Driving (Stunts) did better in CGA mode. Unlike in EGA emulation mode, the replay didn't show any real sign of problems.

Prince of Persia ran well in CGA emulation mode.

Sim City also ran well in CGA emulation mode - I think it runs in 640 x 200 in 2 colour mode, so uses a lot of dithering to achieve the illusion of more shades.

 

For further tests, I'm using the excellent CGA Compatibility Tester v1.28 by Jim Leonard.

Test Category	Test	VGA (Emulation Disabled)	CGA Emulation Mode
SUMMARY		26% Compatible	80% Compatible
Colour Select Register	Border/overscan colour	Failed (border or overscan area should have changed colours)	Failed (border or overscan area should have changed colours)
	Medium res background	Failed (background colour should have been cycling)	Passed (background colour cycled ok)
	High-res foreground	Failed (foreground colour should have been cycling)	Passed (foreground colour cycled ok)
	Medium-res palettes	Failed (low and high palettes were the same for each colour set)	Passed (all palettes shown correctly)
Text Mode Manipulation	40-column mode	Passed (40-column mode filled the screen as expected)	Passed (40-column mode filled the screen as expected)
	Textmode highcolor	Failed (disabling the blink bit to enable all 16 background colours still showed blinking colours)	Passed (blinking was correctly disabled)
	Cursor control	Failed (top and bottom cursors worked, but full block was only a half-block, top-and-bottom line cursor and strikethrough were both blank)	Semi-Failure (top/bottom/full block all ok, but top-and-bottom line cursor and strikethrough were both blank)
	CGA snow	No snow detected, but card may be working to eliminate this	No snow detected, but card may be working to eliminate this
	8x8 font	Passed (thick and thin fonts shown reflect true CGA)	Passed (thick and thin fonts shown reflect true CGA)
M6845 Compatibility	Vertical retrace	Failed (70.0923 Hz detected, true CGA v.refresh is 59.9228 Hz)	Failed (70.0923 Hz detected, true CGA v.refresh is 59.9228 Hz)
	Horizontal retrace	Failed (no moving colour bars)	Passed (moving colour bars shown)
	Row reprogramming	Failed (lots of flashing blocks which shouldn't be flashing)	Passed (stable text image with great use of dithering)
	Row/column reprogramming	Failed (bottom third of the screen is blank, and text is squashed and cut-off in the top two thirds)	Passed (border/overscan area completely absent and text looks normal)
	Interlaced video mode	Passed (Interlaced Mode On is displayed below the standard text)	Passed (Interlaced Mode On is displayed below the standard text)
	Display positioning	Failed (bottom half of the screen is blank, text in the top-half is squashed/cut-off)	Failed (nothing happened!)
	Start address reprogramming	Passed (horizontal and vertical scrolling occurs)	Passed (horizontal and vertical scrolling occurs)
CGA Brown colour		Passed (if this were not implemented correctly it would come out as dark yellow)	Passed (if this were not implemented correctly it would come out as dark yellow)

So in summary, I expect a lot of the CGA tests to fail when running in standard VGA mode - that is pretty normal for a VGA card. When put into CGA Emulation mode the card should match pretty closely what the original IBM CGA card can do, but these cards (or more accurately, their chipset) that don't directly have the hardware present for older graphics standards (usually identifiable as they also have a DE-9 port for digital/TTL output to a monitor) rarely have full compatibility.

 

Hercules / MDA Compatibility

Hercules and MDA are often supported by CGA/EGA/VGA cards. Unfortunately there's isn't a decent utility like the one above for CGA compatibility testing. Instead I'm going to throw some games at the card and run them in Hercules mode. Firstly though, let's see what the card is detected as when MDA and Hercules Emulation is switched on:

NSSI with MDA Emulation enabled - again, ignore the AGP 2x detection due to my motherboard's embedded AGP bus


NSSI with Hercules Emulation enabled

4D Sports Driving (Stunts) didn't run at all well with Hercules emulation mode, with a scrambled screen throughout.

Prince of Persia ran well with Hercules emulation mode. The graphics are clear (for Hercules) and dithering is used to good effect.

Sim City also ran well in Hercules emulation mode - a game that benefits greatly from a higher resolution - this is probably running in the full 720 x 348 resolution the Hercules standard was famous for.

 

Conclusion

So all in all, the Octek EVGA-16 is a pretty standard ISA-based VGA card. It's low on memory which cannot be upgraded to 512 KB or 1 MB, and it's fairly slow for 1991 - probably on par with my 16-bit Cirrus Logic (CL-GD59x chipset) cards. As you saw, it's suffering from jail bars too, and this is not due to anything else in my setup, e.g. the scaler, as other ISA VGA cards I have show no jailbars with this setup.

It does have good emulation capabilities though. After seeing that 4D Sports Driving caused some real problems in both EGA and Hercules modes, I ran several other games to see if the same thing would happen - it did not, but this is far from an exhaustive test. The card does support a number of extended text modes for DOS applications that have the ability to run in higher than 80 columns and 25 rows, and it comes with a large amount of DOS application drivers.

For a 22-year old graphics card, it ran flawlessly over many hours of testing, and didn't complain with the ISA bus being driven at 11 MHz (something my Trident cards always have problems with), so this is one I will clean up and put into my collection for a later time.