It is possible to run 8 GB DDR3 1600 on 790FX?

[MAD5]

I have this board GIGABYTE GA-MA790FXT-UD5P with an Phenom II 955 BE with 2 kits of F3-12800CL8D-4GBTD (4 x 2 GB). So the memory are rated for 1600 but If I put on the bios 1600 it is very unstable. At 1333 with 8 gb no problem at all. It is possible that the chipset only support 1600 on 2 slots and not four? In that case, wich options and timings I should use to get better performance? Thanks.

[GSKILL TECH]

That is correct, the AMD platform will only support 2 slots, but you may be able to get it to work. Make sure Northbridge voltage is 1.4V. Also if you have HT Voltage, make sure that is at 1.4V as well. Let me know if that helps.

Thank you
GSKILL SUPPORT

[MAD5]

Well I try the SB/HT voltage control to 1,4v and the NB voltage control to 1,4v and it runs fine for half hour and then hangs. So I want to try with only 4 gb to test each kit. Wich timigns do I need to use? I try on auto on 1600 and it put me on cas 11 and it is not stable, it is possible that this memory can't run on this motherboard correctly? Can you send me all the timings I need to put? I also try the voltage of the memory on 1,7v and no luck. Try unganged and ganged and the same.

[GSKILL TECH]

What are the default advanced timing values when all 4 sticks are installed? The motherboard may not be picking some of them up correctly, causing instability.

Memory voltage will only need 1.65V max. The memory should always be set to UNGANGED. Let me know the timings and I will be able to further assist you.

Thank you
GSKILL SUPPORT

[MAD5]

Well, I think I found an error on the g.skill webpage. http://www.gskill.com/products.php?index=185
In the main board shows Intel, but in MB chipset, shows Intel X58,X48, P45 wich are correct because all of them are from Intel, but shows at the end AMD 7xx series. I think it should be said Nforce 7xx, like for example the 790i wich is a socket 775 platform. And this memory has xmp wich is also an intel feature, so with an amd motherboard they would work, but with differents and more relax timings, and differentes settings, like in compatible mode. And that's is the reason why I can have even stable only 4 gb kit on 1600 and 8 gb on 1333 works fine, with relaxed timings. Let me know, if what I'm thinking is correct and wich type of memory will work great for this motherboard. thank you for your help.

[MAD5]

Ok, now I put 8 gb again, and can't past super pi 16k. So, it's unstable. These are the timings on auto, wich are different that it was on auto the last time it has the 8gb put on. I remember something like CAS 11, and now on auto it takes CAS 9, wich is very weird, maybe because I change the memory from one slot to another? Anyway, these are all the timings I have on AUTO.
frecuency 1333
cas 9
ras to cas 9
row precharge 9
minimum ras 24
command timing --
twtr 5T
trfc0 dimm 1 110ns
trfc2 dimm 2 110ns
trfc1 dimm 3 110ns
trfc3 dimm 4 110ns
write recovery time 10T
precharge 5T
row cycle 33T
ras to ras 4T
CHA procOdt 60 ohms
CHA DQS 1.25x
CHA Data 1.25x
CHA MEMCLK 1.5x
CHA Add/Cmd 2.0x
CHA CS/ODT 1.5x
CHA CKE 2.0
CHB procOdt 60 ohms
CHB DQS 1.25x
CHB Data 1.25x
CHB MEMCLK 1.5x
CHB Add/Cmd 2.0x
CHB CS/ODT 1.5x
CHB CKE 2.0
bank interleaving enabled
channel interleave enabled
DQS Training Control Skip DQS
CKE Power Down Mode Disabled
Memclock tri-stating Disabled

[Tradesman]

With 8GB you'll have to raise the tRFC and probably the voltages a bit

[RQuallsJR]

I have the same motherboard And processor you have, I had the same problems until I updated the bios to F6. Then set To optimized defualts, (I am useing F3-10666CL8D DDR3 1333 8 Gigs) The only changes I made were to the first four timming numbers 8-8-8-21, And kept the voltage @ auto 1.6v, With no problems. Check your Bios if it needs to be updated to F6. Hope this helps.

[GSKILL TECH]

tRFC will definitely need to be much higher for 8GB, 4 sticks. Let us know how that goes, it should greatly enhance stability.

Thank you
GSKILL SUPPORT

[RQuallsJR]

What settings do you sugest for tRFC? They are set to 110ns right now.

[GSKILL TECH]

195ns should be good enough for 8GB, let me know the results.

Thank you
GSKILL SUPPORT

[RQuallsJR]

I dont have 195ns in bios. I have 90 110 160 300 and 350ns I set it to 160ns and seems to be ok. And ddr voltage is set to 1.6v Thank you for your time and information..

[Tradesman]

Not positive of available settings on your BIOS, maybe 195 or so, or try there and bring it down if okay as long as it stays stable

[RQuallsJR]

What about voltage ?1,6 0r 1.65?

[GSKILL TECH]

Mad5,

frecuency 1600
cas 9
ras to cas 9
row precharge 9
minimum ras 24
command timing 2T
twtr 5T
trfc0 dimm 1 160ns
trfc2 dimm 2 160ns
trfc1 dimm 3 160ns
trfc3 dimm 4 160ns
write recovery time 10T
precharge 5T
row cycle 33T
ras to ras 4T

RQuallsJR,

1.60V should be fine. You can also use the settings above except 1333.

Keep me posted on the results.

Thank you
GSKILL SUPPORT