computer wont boot with Kingston HyperX Savage memory

I am using a Gigabyte 880GMA-USB3 motherboard module and I have just purchased 8GB Kingston HyperX Savage memory that runs at 2400mhz. After installing it in my system, the computer is not posting and there is only a black screen on the monitor. This mobo supports upto 1866mhz RAMs but it should not be an issue because the memory should downclock automatically. The old RAM sticks are still working normally. I even tried the Kingston RAM on other memory but that didnt work. Does this mean that the RAM stick is bad?

The main problem is that your motherboard Gigabyte 880GMA-USB3 supports only 1866mhz RAMs and that is why your computer is not Posting if it is overclocked. I am afraid that these memory modules will not work on your system since it doesnt support those speeds, until you manually overclock it. When you say, the RAM should downclock then it will simply change the voltage and not the speed of the memory module.

Most of the memory modules do not automatically overclock to its advertised speed but should run at 1600mhz by default. After that once you enable the XMP profile in the BIOS, you will get the possibility to overclock it to 2400mhz. Since you have already tried by inserting only the HyperX Savage memory and it is not working so, you might have got bad RAM sticks. If you used it with old RAMs then it might not be working well with other modules.

It might be possible that your Gigabyte GA-880GMA-USB3 might be supporting only 4gb RAM modules so, the 8GB modules are not working. However, if there is any recent BIOS update available for this motherboard then perhaps you can try to flash to the latest bios version for your motherboard and then check if it supports the 8GB memory modules or not. If it is still not supporting after bios update, then it will be good to return the RAM and get a compatible one.