I've been using a GTX 560 for over a year and haven't had any problems with it. Recently I wanted to add a third monitor, so I decided to buy a Geforce 6200 for low-end programs and web browsing. I've now been using both GPUs at the same time, however I've noticed that my computer has been running much slower, even on the monitors that are using the GTX 560. Occasionally everything will freeze and all I can do is move the cursor. When this happens nothing responds to clicks, including the taskbar. Sometimes it returns to normal after waiting for maybe 30 seconds, but other times all monitors go black and I have to shut down the computer by manually holding the power button. I've also noticed that when the 6200 is plugged into the motherboard, the boot time is at least double or triple what it normally is. When I removed the 6200 and rebooted, everything returned to normal.
Is the addition of the 6200 actually slowing down the system? How can I use both cards without running into problems?
There are a few reasons for why this happens, but from what I recall both cards will run at the same clock speed of the slower card and you will have as much VRAM as the lesser card. I do believe that there will be increased performance opposed to running the 6200 by itself, but this is a decrease in power opposed to your 560.
As for your hangups, I would assume there is a conflict with the two cards.