Newbie Front Panel question 8800c and Don C miniFP

[Joseph Corda]

Greetings
Currently do not have a front panel so I've been building a Altair 8800c front panel and interface card (see below) (next will be a Don C MiniFP)

The question I have is concerning the pin outs of the Front Panel  (8 pin Molex connector) to CPU boards (usually a16 pin dip).  I was wondering if there was any standard pin out setup for these connectors so I can build one interface cable for multiple CPU cards or will I need to create a specific cable for each ? 

Are there any docs you can recommend that describing this 8800c FP (and miniFP)  to CPU connection cable?

Thanks
Joe

[Walt Perko]

Hi, 

That front panel interface is for the Altair 8800c front panel board, I don't see how you can connect the 50-PIN ribbon cable to the mini-Front Panel board ... 

On the mini-Front Panel board is the 8-bit data cable in a 16-PIN DIP socket ... you need to make a cable that carries all 8-bits of the CPU board to the mini-Front Panel 16-PIN DIP socket.  

IF you're using an IMSAI compatible CPU board, then it's just the 16-PIN ribbon cable going from the CPU board to the mini-Front Panel board.  

IF you're using an Altair type CPU board that has the 8-bits on the tall fingers, then you need to fabricate a cable that goes from the Altair MOLEX connector on the CPU board to a 16-PIN DIP connector to plug into the mini-Front Panel board.  

Below is a reproduction MITS 8080 CPU board ... you can see the 8-bit data connector in the top right corner ...  Here is the CPU Data connector for the IMSAI ... these are the only connections between the CPU board and the mini-Front Panel board other than the backplane itself.  

                                              

.

[Joseph Corda]

Thanks Walt
So IMSAI and Altair are different 16-pin dip pinouts
Okay I will need to search for documentation for pinouts concerning the Altair Front panel (8 pin molex) to the few CPU cards I plan on using.
Joe

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[Walt Perko]

Hi, 

Okay ... here's the connector from the Altair type CPU board on the left and the IMSAI (min-Front Panel) on the right.  

You can see on the Altair side PIN4 is DATA 0 while on the IMSAI (min-Front Panel) PIN1 is DATA 0 

Essentially the Altair connector goes:  

 PIN 4       PIN 3       PIN2       PIN1        PIN5       PIN6        PIN7       PIN8

DATA0     DATA1    DATA2    DATA3    DATA4    DATA5    DATA6    DATA7

Then on the IMSAI (min-Front Panel) on the right connector:  

PIN 01    DATA0  

PIN 02    DATA0  

PIN 03   DATA1  

PIN 04   DATA1  

PIN 05   DATA2  

PIN 06   DATA2  

PIN 07   DATA3  

PIN 08   DATA3  

PIN 09   DATA4  

PIN 10   DATA4  

PIN 11   DATA5  

PIN 12   DATA5  

PIN 13   DATA6  

PIN 14   DATA6  

PIN 15   DATA7  

PIN 16   DATA7  

You can see the cabling in the photo ... Brown & Red is PIN4 on the Altair side and PINs 1&2 on the IMSAI (min-Front Panel) side.  

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[Joseph Corda]

Thanks Walt...

This is very helpful !

Joe

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[Joseph Corda]

Walt

Question about the adapter cable you displayed..

So I could try to build it with some idc ribbon cable, a 16 pin male DIP crimp on connector to a molex 8 pin connector but I believe 
the IDC ribbon cable I have is just too fine of gauge wire to make a good connection on the Molex side.. 
I notice the DIP side of the cable does not look like a normal IDC crimp type connector.
Can you share any details about the components you used to make that cable ? 

Joe 

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[Walt Perko]

Hi, 

It's a regular very thin ribbon cable ... the Male DIP connector just crimps onto the ribbon cable with the Brown wire at PIN 1.  Then I just twisted the other ends (e.g., PIN 1 and PIN 2 together) and crimped on a MOLEX PIN that fits the MOLEX connector on the Altair side.  

Every two wires get twisted together and installed into the Altair MOLEX connector.  

The hard part is crimping the MOLEX PINs ... get the thin crimper, NOT a spring loaded giant ... 

.

[Patrick Linstruth]

Joe, you may not want to connect all 16 pins like Walt did. Some boards use pins 9-16 for other purposes like rs232. You might send up sending 12v to your front panel board. My cables only wire to pins 1-8 for D0-D7. 

Sent from my iPhone

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[Joseph Corda]

Thanks so much for the feedback
So ...after review  .. I think for the first connector cable build I'm going to use a 16 pin forked male DIP connector and 9 pin wire (and solder). 
I've used this setup before with good luck wiring up a serial connector for my SSM IO4 and it should be more robust than me trying to crimp/solder individual light gauge IDC wires to a molex connector. 

LOL I will let you know if i made a mistake going in this direction ;--)

Joe

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[Walt Perko]

Hi, 

It would be good to know which Altair compatible CPU boards have 12V on the big white MOLEX connector?  The Altair only uses 8-bits (1-Byte) Data to talk to the Front Panel ... and on the mini-Front Panel side (or an IMSAI CP-A Front Panel) the DIP socket is tied 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, and 15-16.  

.

[Walt Perko]

Hi, 

I had one board I got on eBay where the guy had soldered the wire bundle from the front panel directly onto the 8-holes on the CPU board.  I had to unsolder the cable to remove the board for repair.  

OTOH, making a ribbon cable soldered on the CPU board that goes to the 16-PIN DIP plug might not be a bad idea.  Leave the old connector in place, just solder to the backside of the board.  

.

[Patrick Linstruth]

I don’t know of any CPU boards that have 12V on the white Molex connector. There are only 8 pins used for D0-D7 on the Molex.

What I said is I have seen CPU boards with a 16-pin IMSAI-type header that use pins 1-8 for D0-D7 and pins 9-16 for other purposes, such as RS232. I remember thinking I could possibly blow something up if I install the cable backwards. I wish I could remember the board.

So, I don’t think connecting pins 9-16 is necessary or a good idea. I think a front panel cable should only connect those required pins to eliminate a possible problem with a board that uses the other pins for something. There are a lot of different CPU boards with a 16-pin header and people can’t resist using those 8 “extra" pins.

It’s just the way I decided to make my cables.

On Oct 16, 2025, at 11:11 AM, Walt Perko <r4r...@gmail.com> wrote:

Hi, 

It would be good to know which Altair compatible CPU boards have 12V on the big white MOLEX connector?  The Altair only uses 8-bits (1-Byte) Data to talk to the Front Panel ... and on the mini-Front Panel side (or an IMSAI CP-A Front Panel) the DIP socket is tied 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, and 15-16.  

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