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Micom 2000
May 1st, 2006, 03:17 PM
I just saw an Ebay item for an EGA monitor and the seller claimed that "real" EGAs only used a 9 pin connector.

While I know that some EGAs did, in my intense thift-shop years most had 15-pin connectors, usually with some pins missing, which differentiated them from VGA.

I do have a Wyse AT double-card with a 9-pin monitor connection. but I seem to recall the EGA double-card on my IBM AT 5170 was 15pin( it's buried under too many other boxes), otherwise I would have had no means to test the some of my 15-pin EGA monitors with.

Some sort of new urban legend or was he just trying to tout his very overpriced monitors, and accepted some questionable opinion ?

I do have a fair number of TTL configurable monitors that I saved from my move but the costs of shipping from up here in the boonies "North of 50" is prohibitive at this time in computer collecting history.

Lawrence

mbbrutman
May 1st, 2006, 04:43 PM
The seller is actually right .. the original IBM 5154 EGA monitor uses a 9 pin connector.

And if you look carefully, the VGA spec uses a 15 pin connector but three of the pins are 'no connect'. On some very old cables you'll find those pins missing. But they are genuine EGA, not VGA. Newer VGA cables just have all of the pins although they are not needed.

Some classic monitors like the NEC MultiSync can handle either form of connection using a dongle. The circuitry will adapt to what it gets. But the 9 pin connector is real EGA.

Do a Google search for 'EGA pinout' or 'VGA pinout' for more details.

Terry Yager
May 1st, 2006, 07:18 PM
Hmmn, that's strange. I've never seen or even heard of a 15-pin EGA before. None of my service books mention it either.

--T

mbbrutman
May 2nd, 2006, 07:23 AM
Moved to PCs and Clones ..

Starshadow
May 2nd, 2006, 06:50 PM
While I know that some EGAs did, in my intense thift-shop years most had 15-pin connectors, usually with some pins missing, which differentiated them from VGA.

I have a Greyscale VGA that has alot fewer pins than a color VGA, perhaps thats what they were.

Terry Yager
May 2nd, 2006, 10:51 PM
Can you find the pinout, so I can add a copy to my 'collection'?

--T

CP/M User
May 2nd, 2006, 11:43 PM
Terry Yager wrote:

> Hmmn, that's strange. I've never seen or even heard
> of a 15-pin EGA before. None of my service books
> mention it either.

Ditto. My EGA card is an old 8bit(?!?) ISA card - though only
has the 9 Pins.

I know I discovered earlier after posting a program here for
CGA users, that the program could of had a damaging effect
on an EGA - cause VGA, SVGA try to bring some of the old style
compatability back into their cards (with some CGA support).

Is it possible before VGA came out - manufacturers of the EGA
discovered this problem & needed to make a card which would
accept CGA programs? (Hence further development of it & more
Pins?) - merely a thought anyway - or maybe it was a
certainally manufacturers responcibility to make an EGA card
more compatable to CGA?

CP/M User.

carlsson
May 3rd, 2006, 01:34 AM
IIRC, EGA modes include 640x200 and 640x350 but does all EGA cards support the latter mode, or was that an extention along the way?

mbbrutman
May 3rd, 2006, 06:50 AM
EGA included the CGA color modes, but it was not 'register compatible' with CGA cards. So if a program talked directly to the CGA circuitry (the Motorola 6845 CRT controller), it would confuse the heck out of an EGA card.

VGA corrected this .. I think it emulates the 6845 to get rid of the compatibility problems.

640x350 was always part of the EGA spec. I don't think the spec was ever extended. The only variability that I know of is in the amount of memory that can be on the card. Early cards probably have less memory than later cards, which limits what they can do. To do 640x350 in 16 colors requires about 110KB of memory, so a 64K card can't do it.

CP/M User
May 3rd, 2006, 12:47 PM
mbbrutman wrote:

> EGA included the CGA color modes, but it was not
> 'register compatible' with CGA cards. So if a program
> talked directly to the CGA circuitry (the Motorola
> 6845 CRT controller), it would confuse the heck out
> of an EGA card.

> VGA corrected this .. I think it emulates the 6845 to
> get rid of the compatibility problems.

Persisely. The CGA could do some neat tricks (unfortunately I
can't remember where the list was - perhaps Ralf Brown's
Interrupts list has it), which worked well in things like
games. A classic game which dug into the CGA abilities was
Windmill Softwares - Digger (before the game was revised to
work on VGA).

CP/M User.

Micom 2000
May 4th, 2006, 02:46 AM
I guess I had a total misconception on this. I was always looking for VGA monitors (mono and CGA were readily available in the thrifts) and perhaps I assumed unwanted EGAs had the connectors with the missing pins. A quick check of my non-VGA rack came up with only one 9-pin Quad which I know is EGA. So now I have at least 3 more VGAs to fill out my dwindling VGA supply. Some of the 9-pin ones have TTL-Digital switches and could be EGA.
Another lesson learned.

Lawrence