I don't think there is anything that you can do to prevent this. You have to realize that the simulation is not in real time and is naturally slower. This is why the scope flickers. You could try to speed up the simulation by ajusting the TMAX under the Default Instrument Settings in the Simulate Tab. This will help but won't cure it. Try setting it to 1E-03. The only drawback is the introduction of minor errors in the simulations calculation process. This isn't significant but can produce singnals that just don't look like they should (i.e Square waves that are not totally square, Sine waves that are more triangular in shape, etc).
One other option is to use the Transient Analysis function under The Analysis Menu. This by-passes the scope but produces the same results that are viewable through the Grapher. The only thing is that you have to set the time and ouput variables manually with the dialog boxes within the Anaylsis Window. The result is diplayed on the Grapher just like a trace on the scope.
I hope I answered your question and ddn't confuse you. If there is another way. other than what I have suggested, I would like to know too.
I am not sure exactly how you mean "3 min". It took mine only 1 second of "simulator time" which represents what the real circuit timing would be. In "real world time" it took the simulator 25 secs to actually simulate this using all default settings. I am not sure why it would take yours 3 minutes to do this. You could try adjusting TMAX to a lower value to increase the speed, but it seems that there may be something else that is causing your problem with this 1 hz signal..
My set up for this was to use the AC_VOLTAGE_SOURCE alone connected to the O-scope. If your using anything else like the 555 timer or another component to generate your signal then this would lengthen the "real world" time it takes to simulate this significantly and TMAX adjustment would definely improve the situation.
That's about all I have. If soemone else has any suggestions please post them.
P.S.. If your wanting just to generate a signal, use the function generator. I just tested it and it is extremely fast (almost real time). It flies compared to the AC_Voltage_Source that I used in my test. This is something I didn't know so I learned something here too.
On my previous post I just want add a disclaimer. The explaination I gave is the way I understand it. If it isn't correct or I have misunderstood the way things work please let me know. Multisim is a program that is tough to master and something that you will always be a student of. I think I learn something new about it every day and I have had mine for over 5 years (Multisim 2001 Power Pro).
Anyway, I thought I would just put that in there so everyone would know that even though I am experienced with Multisim , I am nowhere near an expert.