I have 2x4 gb 2400 MHz ram running in my PC right now, and my friend got a ram upgrade and gave me his old ram. It's the exact same ram, 2x4 gb with the same latency, same brand and type, even same heatsink, but it's 3200 mhz instead. I tried adding it to the 2400 mhz I already have in my computer and it wouldn't post. Computer would turn on with fans and power LED for about 15 seconds, then turn off for about 2 seconds, then back for 15 seconds and continue like that until I forced a shutdown. After I removed the new ram, it worked fine again.
The slower RAM has always been in slots 2/4. I tried adding the new ram to 1/3. When I took it out, the slower RAM still works in 2/4, and I tried the newer ones and they also work in 2/4. But neither of the 2 pairs work in slots 1/3.
Why is this happening? Is it something I can change in the BIOS? Or by resetting the CMOS?