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Retrom
May 10th, 2017, 07:53 AM
Hi all, just bought a Juko G7-B EGA/Multifunction card (As seen here: http://stason.org/TULARC/pc/graphics-cards/I-L/JUKO-LABORATORIES-LTD-Monochrome-CGA-EGA-G7-B.html) and while it seems to work perfectly in CGA mode, if I configure the jumpers for EGA mode (well, at least what I think is EGA mode, it's just listed as "640x400 Color mode" on the card and the documentation I found online), the card doesn't put out any signal and the computer just gives a bad video card error beep. Any thoughts on what could be causing this? Both the seller and what little information I can't find online both state that this is an EGA card, so I'm assuming it does support EGA mode. Although 640x400 isn't an EGA resolution, as the highest resolution supported by EGA is 640x350 as far as I know, so it does seem kind of odd that the card claims to support that.

krebizfan
May 10th, 2017, 08:30 AM
If it doesn't support 640x350, it probably isn't an EGA. It may offer a mode equivalent to the AT&T 6300 which had an extended CGA mode of 640x400. I can't find anything to confirm that the Juko uses the same signals as the AT&T.

Checking to see what oscillators are onboard might indicate how that mode works. Most of the mid-80s 640x400 hi-res color monitors expected a signal of about 32Hz (maybe 31.5Hz could be more accurate).

Trixter
May 10th, 2017, 08:37 AM
if I configure the jumpers for EGA mode (well, at least what I think is EGA mode, it's just listed as "640x400 Color mode" on the card and the documentation I found online)

That's the maximum resolution, not the resolution you're actually setting (at least, how I read it). You'd need drivers for applications to get 640x400 out of it, otherwise it should produce 640x350.


Most of the mid-80s 640x400 hi-res color monitors expected a signal of about 32Hz (maybe 31.5Hz could be more accurate).

(Assuming you meant 31.5KHz not Hz) FYI, my 6300 monitor is in the 25KHz range for its 400-line modes, not 31.5.

Retrom
May 10th, 2017, 08:47 AM
That's the maximum resolution, not the resolution you're actually setting (at least, how I read it). You'd need drivers for applications to get 640x400 out of it, otherwise it should produce 640x350.

That's what I was thinking. But the computer doesn't detect the card when I try to set it up this way, it does work in CGA mode though.

Trixter
May 10th, 2017, 10:09 AM
Found an advert in PC World Vol 5. 1987 page 162 -- turns out it's not an EGA card. It's an enhanced CGA and Hercules card. The text on the photocopy is hard to read but here's what I can make out:

- Color Display Adapter compatible
- Hercules Graphics Card compatible (720x348)
- Connects to Composite Mono/Color Monitor
- Connects to 640x400 Hi-Res Color monitor
- Connects to to PAL/NTSC/SECAM system TV
- Microsoft bus mouse compatible
- Parallel printer port and game port
- Light Pen Interface

So the 640x400 support is if you want to hook it up to a 400-line monitor. Since those are even more uncommon than EGA monitors, just use it like a CGA card.

Retrom
May 10th, 2017, 10:27 AM
Ah crap. Well maybe I can get a partial refund from the seller, given that his listing described it as an EGA card. Thanks for the info, Trixter.