Appears to select between the extra non-standard clock oscillators.

EGA should only have 16.257MHz oscillator and it also utilizes the 14.318MHz from ISA bus.

The 27.256MHz and 25.000MHz are non-standard extra oscillators for an EGA card.
Could allow compatibility with other monitors instead of standard CGA/EGA monitors, or, custom resolutions with standard CGA/EGA monitors.

hmmm could these be used so that the card is classified as "Super EGA" with 480lines resolution instead of 350? I have read about later EGA cards supporting higher resolutions but my knowledge of that era is pretty limited.
I suppose I can verify the xtal connections once I receive the card.

I own various EGA cards and they all have three oscillators.

^ do you use them? What's the deal with the 2 RCA jacks? are they composite-out ports? and why there are 2? 😁

keropi wrote:

What's the deal with the 2 RCA jacks?

If you can track them to the feature connector, you can safely forget them for ever. I'd be surprised if someone is aware of anything meant to be connected to it.

I think that most of the short EGA cards do "Super EGA" modes, so all of yours having three oscillators are not that surprising.
The most common Super EGA mode was 640x480 (VGA modles 11 and 12), but many cards also offered 800x560 and some weird in between resolution.

Something I have been reading about that we really take for granted is video mode "Auto Switching". As I understand it, prior to this feature being popularized by cards like the Paradise EGA Autoswitch, you would have to manually initialize the desired video mode before starting the software you wanted to run. From what I can tell, some pre-autoswitch cards could be manipulated via software after rebooting the system, but I suppose others required jumper changes.

BTW, I'd be very careful about playing with any of the Super EGA modes if you don't have a multi sync monitor. It's possible to fry a standard EGA display...or so I've been told.

Good to know. I don't plan on using anything other than what games use - I assume it's the standard 640x350 max. The "good" thing is the the Olivetti 286 that was paired with the monitor also had an onboard PEGA2A 256kb ega card with the dip switches block next to it. I'll just put the same setting on the stand-alone card I bought and be safe 😁

I received the card but the jumper settings are still a mystery:

- J2 under the BIOS
- J3 block under the 3 crystals
- J4 under J3

A really wild guess is that J2 is used for selecting the card's address range?

I was able to figure out the DIP SWITCH block using the info in this thread: http://www.vcfed.org/forum/showthread.php?230 … se-WD-EGA-cards , I had to put SW5 to OFF else my 286 would not boot - it would hang with a blinking underscore (SW5 is monitor "auto configure")

It would be nice to know what the rest of the jumpers did, maybe it's something interesting/useful 😕