I have two RAM cards in my PC, they worked fine before but after my BIOS being reverted, it's causing the text to be scrambled to something I don't understand. I tried removing one of the cards and the text looks normal again, but when I put back the card i've removed the text goes funny again. I tried switching them places, and it turned out one of my card is having a problem but I don't know how to troubleshoot it. How can I use both cards again?
It could possibly work together if you were able to adjust the memory timings off of the default settings.
Run memtest86 to keep checking, you would not be done when it "just doesn't error" There are possibilities for tiny unseen ram error that can cause corruption and crashes and other bad things. Without a full test, you could continue to have problems, even worse ones, when it seems ok but is a bit off.
The memory might also work if the memory divisor was set lower, which would reduce the memory speed by larger quantities, also the voltage fed to the ram might change the overall stability.
Although I still would agree with Ignacio that the costs of memory are down enough to get a good "Team" of the same type, brand, manufacture, and even batch. It might even be on the Compatability list for the manufacture of the computer/motherboard. Manually re-timing memory for the motherboard and testing to be positive can take a lot of time, and number of fails.
If I had to pay a shop for re-timing and tuning memory I have done, I could have easily afforded the best memory out there :-)
You likely can't.
To be fair, you could, if you replaced one or more of the chips on the damaged module. But the equipment to do so would be more than the cost of a new set of modules.