No Boot With +16GB RAM - 990fx Killer

kwag_myers wrote: Why can I not get 32GB of RAM @ 2400 MHz into this board?

Because AMD only certifies the 8350 to run with two sticks running at 1866. Above that it's on your shoulder to coax an overclock out of the MB/CPU.

What's holding you back is most likely the IMC. But even then, as all silicon is not created equally, it's a crap shoot to just how high yo can coax four sticks as four sticks places a great stress on the IMC.


Look in your BIOS for a single line that reads CPU/NB Voltage. This is the voltage that the IMC relies upon to "feed' it. Bump it up one bump in the BIOS at a time, testing between bumps. Too, keep an eye on your temps.

You should not need to get near 1.25v but like I said, all silicon is not equal.

DO NOT just read this and change it 1.25v ! One bump at a time till you find it boots. You may, after finding where it'll boot, run a short stress test and find it fail. Simply offer it another bump in the BIOS and you should be golden from there.

You also might check that all four sticks run at 2133 before doing the above.

I'll add a bit to wardog's post. Let's start with this picture from AMD:



Like wardog already stated, AMD certifies the FX-series CPUs to run with two sticks running at 1866 MHz. However, this is only the case when there are only two memory slots on the motherboard. If there are four slots, it's 1600 MHz even if you only have two sticks. Four slots and four sticks is the same thing, as long as you have single rank memory. If not, the certified speed drops to 1333 MHz.

I couldn't find any mention of the rank of your sticks on Corsair's site, so I'd start with 1333 MHz and work my way up from there. You might be able to hit 1600 MHz or even 1866 MHz without touching the CPU/NB voltage, so start by finding the point at which your system becomes unstable. You can try bumping the voltages after that, if you're not happy with the speed you're achieving.

There are two other things to keep in mind:

1. RAM speed does not really affect everyday performance. You will most likely only notice the differences between different speeds in synthetic tests and a very limited amount of applications (like winRAR or video encoding). So don't feel too bad about the less than perfect IMC.

(This is a bit old, but I believe the main results are still valid and the article also does a good job explaining the basics about RAM:

http://www.anandtech.com/show/6372/memory-performance-16gb-ddr31333-to-ddr32400-on-ivy-bridge-igp-with-gskill)

2. If you're running your RAM at a lower speed than what it's rated for, you can compensate that by changing the timings. For example, at 1333 MHz the SPD latency values for your sticks are 9-9-9-24, while at 2400 MHz the tested values are 11-13-13-31.

Assuming the problem is not related to the sticks themselves, you should be able to boot with four sticks at 1333 MHz. If they're single rank, then 1600 MHz should work as well. If not, even 1600 MHz is an overclock and may not work without extra voltage. You may also need to increase RAM voltage to achieve stability.

Some more reading (pages 15 and 19 at least):

http://www.amd.com/Documents/AMD_FX_Performance_Tuning_Guide.pdf

Btw, don't change the NB voltage, change the CPU/NB voltage. These are two different things (see the tuning guide for details). Leave the NB at its stock voltage 1.10V. The CPU/NB stock voltage is 1.15V and that's the one you want to increase if need be. Just keep an eye on those CPU temps, since the CPU/NB (the memory controller) is located on the die itself.

wardog wrote: hehehe 1.40 to the NB. Gadzooks man. hehehe, noob

I guess you can't believe everything you see on YouTube (2:29).

Things are not going well in Kwaggie's mire. I tried all frequencies from 1333 to 2133 (with the CPU NB at 1.625 and 1.2375) and all CPU NB voltages between the default 1.1625 and 1.2625 (I know, but I had to try). I'm currently running three sticks at 1333 with the CPU NB at 1.1625. I haven't touched anything else since resetting the CMOS. I'm not sure what to do next, so unless there's another suggestion, I'll have to go with this (still six times what my old machine was, RAM wise). Would it be worth the time to try each frequency with each voltage (stopping at 1.25, I promise)?

fyi, I was wondering how I could have missed the CPU NB setting before until I realized I had to switch the Multiplier / Voltage Change to Manual in order for it to display.