SIO and two computers?

[joeatari]

Is it okay to connect two different computers to your sio chain as long as you don't access your peripherals at the same time with both computers? For example a 130XE and 800XL using the same drives and printer?

[Gunstar]

It should be fine as long as only one computer is on at a time. I think I did that about 15 years ago, actually.

 

But I decided very soon that I wanted to be able to use both computers at the same time and so I added a switch to my APElink multi-SIO that switched between the two SIO ports that went to the two computers. I forget exactly how I rigged that, it worked fine, but I have long since removed it as I now have complete systems, as much as I need, and no need to share peripherals anymore.

 

I was just thinking about something similar just yesterday though, but creating a switch box for the SIO just like those old VGA and RS232 switch boxes to connect up to 4 Atari's to the same SIO chain. Just a simple manual one.

Edited March 24, 2019 by Gunstar

[_The Doctor__]

No you must first diode protect the sio ports or add a switch between the them !

 

Depending on the Atari's involved you will back feed either 5 volts or 12 volts to the other computer. This browns out the first and kills the power supplies.. among other issue!

Edited March 24, 2019 by _The Doctor__

[Mathy]

Hello guys

 

Try the automatic two computer interface.

 

 

Sincerely

 

Mathy

[Gunstar]

No you must first diode protect the sio ports or add a switch between the them !

 

Depending on the Atari's involved you will back feed either 5 volts or 12 volts to the other computer. This browns out the first and kills the power supplies.. among other issue!

Thanks for catching error of my bad memory. That's probably what I figured out years ago which lead to the switch on APElink. I should have pondered more before replying.

[+bob1200xl]

You should be able to connect two 1200XLs to a 1050, for example. Plug an SIO cable from each computer into one of the SIO connectors on the same 1050. You should be able to run either system from the I/O you have connected. In fact, all the I/O on both systems should share.

 

The problem is with other computers that power the SIO interface. Each system may send +5v (or even +12v) into the SIO. The 1200XL (unmodified) has a 100 ohm limiting resistor on +5v, so it should be OK. Other systems may not be OK.

 

Don't try this with tape drives like a 410 or 1010. They use MOTOR ON on SIO. You would have to look into that.

 

Bob

[Gunstar]

You should be able to connect two 1200XLs to a 1050, for example. Plug an SIO cable from each computer into one of the SIO connectors on the same 1050. You should be able to run either system from the I/O you have connected. In fact, all the I/O on both systems should share.

 

The problem is with other computers that power the SIO interface. Each system may send +5v (or even +12v) into the SIO. The 1200XL (unmodified) has a 100 ohm limiting resistor on +5v, so it should be OK. Other systems may not be OK.

 

Don't try this with tape drives like a 410 or 1010. They use MOTOR ON on SIO. You would have to look into that.

 

Bob

That clears up my mystery and bad memory. That's why it worked for me, because I had 2 1200XL's at the time, though I do think I might have already added +5V fix to one of them...maybe not. I still had my 130XE at the time, but it was separate with it's own MyIDE HDD.

Edited March 24, 2019 by Gunstar

[joeatari]

Thanks for all the great information. I'll ponder this and decide if I will build something

[+bob1200xl]

As long as one, not none, of the 1200XLs has the 100 ohm resistor in R63, it should be OK.

 

Bob

 

 

That clears up my mystery and bad memory. That's why it worked for me, because I had 2 1200XL's at the time, though I do think I might have already added +5V fix to one of them...maybe not. I still had my 130XE at the time, but it was separate with it's own MyIDE HDD.

[brenski]

quintopus deluxe will do two computers/multiple devices (two-switches).

Edited March 31, 2019 by brenski

[jcbstein]

This is how I do what your asking about.