Question Boot trouble following RAM upgrade

Jul 17, 2019
Hi there, I'm an engineer (evidently the wrong kind) and novice PC builder hoping for help with what I expected to be a simple upgrade:

Motherboard: MSI X99S Gaming 7
CPU: i7-5820K
Boot Drive: Samsung 850 EVO
RAM (Config 1): 16 GB (4x4) DDR4, 2400 MHz, 1.2V [ADATA Something Offbrand]
RAM (Config 2): 32 GB (2x16) DDR4, 3200 MHz, 1.35V [Corsair Vengeance LPX]
RAM (Config 3): 32 GB (2x16) DDR4, 2666 MHz, 1.2V [Corsair Vengeance LPX]

I put this PC together several years ago without any problems, though I've always had some boot-up strangeness. With RAM Config 1 I basically always boot to a black screen with "A2" in the bottom corner. Either power cycling or hitting reset will allow the computer to boot normally to Windows.

I recently tried moving to RAM Config 2, but the computer will not boot. Instead, it powers on for a few seconds and powers off, without getting as far as the option to go to BIOS, or even far enough to send a video signal to the monitors. Swapping back to Config 1 resumes the previous behavior of the computer, with the annoying double-power-cycle requirement but otherwise being fully usable.

With RAM Config 1 installed I attempted through overclocking tools (both in Windows and in BIOS) to manually set the DIMM Voltage to 1.35V from Auto, in case Auto wasn't working for some reason. This did not improve the behavior once I switched back to RAM Config 2.

I checked the specs for the motherboard, and while it lists compatibility with a wide range of specific RAM frequencies up to 3333 MHz, it does not specifically list 3200 MHz. For this reason, I traded in the 3200 MHz stuff for 2666 MHz, RAM Config 3. Config 3 is also 1.2V RAM, the same as my previous successful configuration. Unfortunately, Config 3 behaves identically to Config 2.
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So config 1 kind of works but with an A2 debug error. Looking around regarding A2 code seems to refer to ide detect. Have you looked into this code?

How many sticks is config 2 because 2x 8 doesn't equal 32 :p

Which slots are you using? See quad channel with 4 sticks.

Going back to A2 debug, try disconnect any other drives you may have and possibly the ssd and see if the system boots properly. Is the bios updated to the latest?

Could be a coincidence of multiple problems between whats causing A2 and trying to get different ram running.
Jul 17, 2019
Oops, sorry, 2x16 for Config 2 and Config 3. My ultimate goal is to get that 32 GB config working, with the A2 error with the original memory as context.

Anyway, with the 4x4 arrangement I do have them configured in the way recommend at that link (same as in the motherboard manual).

I had previously messed with the boot drive order, but I don't before that I've actually disconnected the secondary HDD (spinning dish with more capacity than the boot SSD). I'll give that a shot first, and then move to having them both disconnected.