ISA extender with ribbon cable

[Mills32]

In the future, I might want to create a small case (Amiga style) for a 286 12 Mhz pc, and it will only fit there if the ISA cards (VGA, SBLASTER and sd card/HD adapter) are located in weird horizontal positions, parallel to the motherboard (and on top of it), also far from the ISA connectors themselves.

So I'd like to create some kind of ribbon cables to connect the cards. Is it possible to create ISA extenders using common ribbon cables?.
I read this could cause trouble, because ribbon cables will weaken the signals, and the cards won't work, but I think they were talking about faster machines, like 486.

Thanks!

 

[Chuck(G)]

Maybe, depends on the length. An inch or two should be okay; after that, crosstalk and various transmission-line issues will likely rear their ugly heads. I recall that the Visual Commuter portable connected its single ISA slot to the motherboard using a ribbon cable.

 

[Mills32]

Maybe, depends on the length. An inch or two should be okay; after that, crosstalk and various transmission-line issues will likely rear their ugly heads. I recall that the Visual Commuter portable connected its single ISA slot to the motherboard using a ribbon cable.

The vga and sblaster have to be around 8 inches away from the isa connectors :shocked:. I also read you can use capacitors to keep signals ok, but I just don't know. There is not a lot of info about this, I hope this doesn't damage the cards if some day I test it.

 

[Chuck(G)]

I doubt that there's any possibility of damage to the cards--you'll mostly see issues crop up by erratic operation, should they arise.

 

[Hak Foo]

I wonder if you could repurpose the riser card from a slimline desktop PC? If you're looking at three cards, that might be the way to go.

I recall an old 8086 machine (the completely absurd Panasonic Executive Partner) that had an ISA slot implemented by a big ribbon cable from the mainboard, but it was probably less than 10cm long.

 

[Mills32]

Maybe cables are going to be a bit too long , But it would look so cool!. This is the "thing" I made, using more or less accurate dimensions, and leaving plenty of room for cables and cards not touching etc...

 

[Chuck(G)]

What will you do for cooling?

 

[Mills32]

What will you do for cooling?

I don't think a cooling system is needed, i used this pc for a long time one day (it is inside a modern case with the sides open), and it never felt hot, or even warm at all. Maybe the psu needs a little fan or just a hole, and that's all.

 

[soviet9922]

Have done ribbon cables for my tandy 1000HX, to place an isa card externally (the computer don't have space inside) the ribbon is 10cm long, and xt-ide cards and adlib they works fine.

 

[Mills32]

Have done ribbon cables for my tandy 1000HX, to place an isa card externally (the computer don't have space inside) the ribbon is 10cm long, and xt-ide cards and adlib they works fine.

Thanks!

So they are just cables, nothing more?, (like capacitors or anything else?)

 

[Chuck(G)]

My recollection is that the Visual Commuter used a standard crimp-on PC edge connector for its ISA connection. Nothing fancy.

 

[bladamson]

Not mine, but is this what you are looking for?

https://oshpark.com/shared_projects/cG4aZUEg

I used to use these in a PS/2 Model 25 with a 7 slot external ISA backplane sitting behind the machine.

 

[Hugo Holden]

Maybe, depends on the length. An inch or two should be okay; after that, crosstalk and various transmission-line issues will likely rear their ugly heads. I recall that the Visual Commuter portable connected its single ISA slot to the motherboard using a ribbon cable.

I built a 8 bit ISA card extender for working on faulty cards for my IBM5155. I used flat ribbon cable about 1 foot or more long, there were definite issues due to cable capacitance, inductance. To solve the issues I added additional filter capacitors (Tantalum & ceramic) on the power supply lines at each end and placed 22 Ohm resistors in series with the signal lines, this fixed it and so far the card extender has worked well with every type of card I have tried it with, but not with every card without those additional parts.The resistance damps the ringing.

 

[soviet9922]

Thanks!

So they are just cables, nothing more?, (like capacitors or anything else?)

Only a flat ribbon cable, easy to do no need to add caps or anything. Also tested the card using this and worked fine.
Of course the ribbon is short 10cm not more, if you do a longer one may need extra hardware not sure.