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IBM EGA Feature Connector Card

Shadow Lord

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Jun 16, 2010
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Hello All,

I recently purchased an IBM EGA Card w/ the 192KB memory expansion from one of the VCF members. To my surprise there was also included a smaller card which connected to the feature connector on the EGA card. My research in the OA volumes and HMS have not yielded any info on this card. Googlefu has also been less than helpful except for one link to an outdated price sheet listing the card for $75. Checking with the seller, he is not quite sure what the card is for either, but he thinks, it may have been a custom card for something at Dupont. I wanted to get the hive mind opinion on the card and see if any one can recognize the card or can shed any light on its purpose. TIA!

IBMEGACard.jpg


IBMEGAFeatureConnectorCard56X2363Front.jpg


IBMEGAFeatureConnectorCard56X2363Detail1.jpg


IBMEGAFeatureConnectorCard56X2363Detail2.jpg


IBMEGAFeatureConnectorCard56X2363Back.jpg
 

mikey99

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NC , USA
Very cool ! I've seen many IBM EGA cards over the years but have never seen anything attached to that
feature connector ! If we had the pinout of the feature connector interface it might help reverse engineer
and learn the function of that card.

I did find this link below, but doesn't mention the function of the card.
http://www.computerhistory.org/collections/accession/102691932

EDIT: Looking at those two chips, it may be an external clock of some sort, the clock rate controlled by the resistor values.
I think this may have been used to change the clock rate of the EGA card to support different (probably higher) resolution
monitors. Also, I found the feature connector pinout on modem7's documentation site ....page 78 :
http://www.minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf
 
Last edited:

Shadow Lord

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I did find this link below, but doesn't mention the function of the card.
http://www.computerhistory.org/collections/accession/102691932

EDIT: Looking at those two chips, it may be an external clock of some sort, the clock rate controlled by the resistor values.
I think this may have been used to change the clock rate of the EGA card to support different (probably higher) resolution
monitors.

Cool Find mikey99. I didn't find that picture when I was looking. Interesting thing with the wire there. Mine doesn't have the wire and I am not sure even if it did it would get connected in the middle of the feature connector pins (sort of gets in the way of connecting it to the EGA board ;)). Also of note:

The one you linked to lists the number 875153 mine has 857148 and D/C 4587 vs. 1686. No idea if it is significant but those differences are there as well.
 

deathshadow

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Jan 4, 2011
Messages
1,357
I might be wrong, but the last time I saw a EGA feature card like that, it was to recombine/create sync on green for displays that had the three separate RGB inputs as coax. DEC, Wang and Sun all made 17 to 24" CRT displays that could handle EGA's resolutions and signal levels if you could combine the 2 bit color channels into analog and put sync on green. Was one of the reasons the feature connector had both RGB outputs and inputs on it.

Wang for example had a workstation display that was 20" (I had one) which accepted 6 inputs or RGBrgb as their own separate coax connects... worked great with the EGA card if you could break it out and get the proper sync frequency on G... which I did with a little external protoboard... no reason that couldn't have been handled on the feature connector.
 

deathshadow

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Joined
Jan 4, 2011
Messages
1,357
From an old text document:
Code:
EGA feature connector
-----------------------------------------
pin     Signal                  Direction
1       GND
2       -12v
3       +12v
4       J1
5       J2
6       G' Out                  Out
7       R' Out                  Out
8       B' Out                  Out
9       ATRS/L
10      B Out                   Out
11      G Out                   Out
12      G                       In
13      R'                      In
14      B                       In
15      R                       In
16      R Out                   Out
17      FEAT 1                  Out
18      BLANK
19      FEAT 0                  Out
20      FCI                     In
21      FCO                     In
22      G'/I                    In
23      B'/V                    In
24      HIN                     In
25      VIN                     In
26      14Mhz
27      Internal                Out
28      EXT Osc                 Out
29      V Out                   Out
30      H Out                   Out
31      Gnd
32      +5v

Looking at the back of that board, it does appear to be running clock output to the green input on pin 22, amongst other places... so yeah, I suspect that's a 'sync on green' board.
 

mikey99

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NC , USA
I found some more details about the feature cards in a PC Hardware Book .... I posted a section from the book below
that describe the card. I suspect there may be different variations of these feature cards as this one clearly shows
a wire that attaches to a GPIB card.
 

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Chuck(G)

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I doubt that it's an oscillator of any sort--there are no capacitors, just resistors.

I can't quite make out what traces are connected to what. If you can draw a schematic of what's on the board, the answer to what it does should be obvious.

My guess is that it might be a SOG (sync on green) adapter.
 

Shadow Lord

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I found some more details about the feature cards in a PC Hardware Book .... I posted a section from the book below
that describe the card. I suspect there may be different variations of these feature cards as this one clearly shows
a wire that attaches to a GPIB card.

And now that we have a real name finding info is easier:

VCF Linkage

Little blurb in Computerworld

Infowindow Parts List

I love the hive mind :D
 

billdeg

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Nov 18, 2003
Messages
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Location
Landenberg, PA USA
I am glad to see this card resulted in a fun project. I am the seller of the card by the way, I have one more just like it I believe...so when I get the chance I will spend more time with it. I should have the docs but so far I have not found them. As Shadow Lord said, I claimed it was originally from DuPont, at least that's my guess. When you live in Wilmington Delaware everything IBM that pops up from that era was a DuPont item. When during that time I worked at IBM and then DuPont so many crazy custom video cards went through my hands. It seemed to me like IBM would pull up to the loading docs with an 18 wheeler full of IBM PCs and stuff and DuPont was like 'what do you have for us this month?" It was amazing.

I also remember these huge rooms full of DEC VAX tape drives whirling away, and shelves and shelves of 80's IBM PC stuff. My job then among other things was to put together custom systems from all those parts to spec.

Anyway, I have a lot of that stuff, they used to let me take whatever they no longer needed, when the PS/2 was in full force they didn't need the old IBM PC's anymore. I did not really go crazy about taking things though. Just one nice working system or two. Perhaps in hindsight...

Bill
 

Shadow Lord

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Now, that the mystery is solved how about a question: Has anyone tried an IBM EGA card in a modern system? I first tested the card in a P90 system w/ 16bit ISA slots and the system would not boot. I just got one long unending beep. Popped it into the 5170 and it worked like a charm. Not sure what the problem is as other EGA cards work fine in the system. I am guessing it may have to do w/ the BIOS address space but I am probably way off base.
 
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