GA-970A-DS3 Rev 1.0, upgrade to 16 GB RAM won't boot

have you reset the cmos when swapping ram.....it could be a non default setting set in it

Looking at Gigabyte's website for that board, it gives the strong impression that your motherboard was never released in an AM3 "non plus" configuration.

FX series CPUs are AM3+, so the memory controller is rated at up to 1866 MHz for memory support, but that doesn't mean your board or CPU is going to stably run the memory modules at that speed. Furthermore, you're not going to see significant performance over say, 1600 MHz memory, so in the end, if you can't run at the rated speed of the memory, I wouldn't be too concerned.

An FX 4100 CPU is based on the original Bulldozer architecture, and the memory controller in the Bulldozer series and later FX chips is terrible, having lower compatibility than the Phenom II CPUs that preceded them.

Your best bet is to go into BIOS and manually set your RAM to 1333 with the working set or a module from the working set, then try booting a single stick of the new RAM.

The manual does not make any special mention for which slot is preferred when using only a single module, giving only guidelines for dual-channel module configurations. With this in mind, you might as well try all four slots, after having configured the 1333 speed, starting the slots the manual lists as, "use first."

After you've set a compatible speed in BIOS using your working memory, start with a single module in DDR3_1, which is the socket closest to the edge of the board, or furthest from the CPU socket. If that fails to boot with the new module, try DDR3_2, which is the 2nd socket from the CPU socket, followed by DDR3_3, or the 3rd socket from the CPU socket, and finally, DDR3_4, the closest socket to the CPU.

If you can boot the system at 1333 with the new modules installed, you should be able to try setting the BIOS to use an XMP profile for the memory. If you can do that, it may just configure everything for you without any further need to fine tune things.

Keep in mind, if you can't get an XMP profile to work for you, you may have to manually adjust the voltage for your RAM to get it to run at it's rated speed, or even some lower speeds. Make sure you check what voltage is going to the memory modules and adjust it according to what the memory you purchased is actually calling for.

a lot of older mb dont like low power ram. that ram is 1.35v ram. look for older 1.5v ram.

If devices were configured a certain way to enable the correct boot sequence, resetting CMOS likely changed that.

Often times other hardware devices such as 3rd party USB or SATA controllers can be enabled or disabled, or be set in IDE mode, which you don't want for best operation.

After resetting your CMOS, provided you can get into it, you need to go through each setting and make sure it's set correctly. If you don't know how to do that, you shouldn't be wiping the settings, but what's done is done.

In the future, the best thing to do is take snapshots of each BIOS settings page with your cell phone camera or other digital camera so you can reference the previous, working settings.

So, if I understand correctly, with the memory speed set lower, you can now get into CMOS with the new modules? This is a good place to start troubleshooting.

Wouldn't be the first time that BIOS had bugs in it. Glad things are scooting along for you though. That's always the best outcome.