Where to start with underclocking my new F3-2400C10D-16GTX

[AGuyInPhoenix]

Motherboard GA-990fxa-ud7
Processor FX 8350 Black
Ram G.SKILL Trident X Series 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 2400 F3-2400C10D-16GTX

My question, Where should I start with setting these up? I understand my MB can handle 2000MHz but the processor is only rated for 2 sticks, 1 per channel at 1866MHz. And since these 2400MHz models were $5 cheaper than their sister 1866MHz ones I figured with these I would have the ability to keep them later when I upgrade things. But I am hoping someone would know how I should set the voltages and timing when I install them. I hope to be able to have these tighter and still stable than what I could have the 1866MHz versions at because I figure these must have better components, But that someone on here must be better at this than I and maybe even have some experience in underclocking.

I thank you for your time and help.

[Priller]

1866 CL8-9-9-24


2133
CL9-11-11-29
9T
160ns
16T
9T
41T
6T

Bump CPU/NB to 1.25 Volts. Ram at 1.525V at 1866 and 1.675V for 2133+.

Just a rough baseline to start with.

[emissary42]

Most FX-8350 have no problems hitting DDR3-2400 with manual settings on a decent board. Some can even do it with four modules, but most people don't want to bin several CPUs just for their IMC capabilities.

Primary Timings for that kit, from lower to higher clocks (tCL-tRCD-tRP):

7-8-8
8-9-9
(9-10-10 / 9-10-11)
9-11-11
(10-11-11 / 10-11-12)
10-12-12

Start with a Vdimm of 1.65V and lower it when you found your final memory ratio and timings. Also the F3-2400C10D-16GTX probably need a tRFC of 300/350ns like most other 2x8GB kits on AMD.

[AGuyInPhoenix]

Wow I umm.... Wow... Apparently I have a lot more reading I need to do before I install these because your responses sound like they have all the information I need to get it done but I don't know what you said, lol.

This section here:
9T
160ns
16T
9T
41T
6T

I dont even know where to start with that...

[GSKILL TECH]

Take a look at this guide:

http://www.gskill.us/forum/showthread.php?t=11742

[AGuyInPhoenix]

I actually read that before first asking my questions but it didn't really help me out, I thought I would post my screens because I can't get anything stable over the default 1333.


The 1333 defaults

and 1866 defaults, the lowest of my goal speeds.


I tried the settings recommended above correctly I think and didn't get it to boot.

But ya, my goal is to get it to 1866 at least, but I can't even figure out a stable point at 1600.

[emissary42]

memory clock 1866
ddr3 timings manual/quick
command timing auto (2t)
cas latency 8
ras to cas r/w 9
row precharge 9
minimum ras act 24
twtr auto (6)
trfc0/1 300
write recovery auto (10/12)
precharge auto (6)
ras to ras delay auto (6)

Go to voltages and adjust Vdimm / memory voltage to 1.6V if needed. Likewise for DDR3-2133 set

memory clock 2133
ddr3 timings manual/quick
command timing auto (2t)
cas latency 9
ras to cas r/w 11
row precharge 11
minimum ras act 28
twtr auto (8)
trfc0/1 300
write recovery auto (12/16)
precharge auto (8)
ras to ras delay auto (7)

And keep Vdimm / memory voltage at 1.6V. You might however have to adjust/raise IMC voltage a bit. How much you have to test for yourself, but don't go all out on it (+0.03/+0.05V are probably enough).

[Priller]

Here is the settings I use on my Tridents for 1866.

It's not perfect as I am using a profile for some of the secondary timings and I havent finished fine tuning it just yet.

EDIT: One thing to note is that you have to put in 1.525V to get 1.504V. If you leave it at 1.500V you will only see 1.488V.

On my UD7 you need to put in 1.680V to get 1.656-1.66V VDimm.