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Need HELP with RAM for FX 8350

Hello community!

I have a situation on my hands that I need to figure out. So first off, I just recently built an AMD based gaming/workstation PC. These are the specs:

Motherboard: ASUS Sabertooth 990FX
CPU: AMD FX 8350 "Vishera"
GPU: Sapphire Radeon HD 7970
RAM: Patriot Viper Xtreme 8GB
PSU: Corsair HX850
etc. etc.

So my question is in regards to RAM. I'm looking to upgrade my RAM kit but I'm a little confused as to what's supported natively in the memory controller for the Vishera chip and what's supported on the Sabertooth mobo.

I read somewhere that the FX 8350 supports 1866 RAM in dual channel mode, but when in a quad channel setup the speed is throttled down to 1600. So does this mean that if I buy a quad channel kit @ 1866, the CPU will only support 1600 speeds? Would buying a dual-channel kit be the only way for the CPU/RAM to natively utilize 1866 speeds?

I've been looking at this kit from G.Skill that is a dual channel 1866 16GB kit with an incredibly low CAS:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231623) that seems to fit my needs

If I were to buy the same RAM (1866) but in a quad channel kit, would I be losing that 1866 speed? Is this RAM even supported by the mobo?
10 answers Last reply Best Answer
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  1. Best answer
    From what you said yes, the CPU will only support the speed of 1866MHZ while in a dual channel config, if you use a quad channel config it will turn the memory down to 1600MHZ

    Your link isn't working for me.

    While the memory would operate at 1600MHZ it would also probably operate at a lower timing but you would probably be better of going with a 1600MHZ memory since its cheaper. Going faster on memories is not always helpful since the timing also goes up, the best bet is to find the memory that has the lowest timing for the frequency that fits your hardware.

    For 1600MHZ memories the lowest timings i came to find was 7-8-7-24 but recently the best i got when i updated my system was 9-9-9-24
  2. Ok perfect! That's just the answer I was looking for.

    As for timings, would 7cas @ 1600 vs 8cas @ 1866 really make a huge difference? Which would perform better?

    I'm really just looking to squeeze the best performance paired with my 8350 with the next RAM kit I purchase, regardless of price.

    Sorry for the broken link, below are 2 kits I'm looking to buy. Which would perform better in both gaming and video editing?

    http://www.newegg.com/Product/Product.aspx?Item=N82E16820231623

    VS

    http://www.newegg.com/Product/Product.aspx?Item=N82E16820231537
  3. I would recommend going with the 1600MHZ model, like i said the timing usually even out the difference of speed so you're left with going dual channel or quad channel and i guess that's an easy choice.
  4. SR-71 Blackbird said:



    Wouldn't the TridentX series be better due to the lower Cas latency? It's also dual channel @ 1866
  5. Best answer selected by TheStrayWulF.
  6. SR-71 Blackbird said:


    Hey Im doing a build now with the same processor and mobo. How do you like the Sabertooth and what RAM did you decide on? Any issues?
  7. From this i guess that FX dual channel is not nativly possible on 1866Mhz?
    And what is this " HyperTransport™ Technology up to 4000MT/s full duplex, or up to 16.0GB/s I/O Bandwidth
    Integrated DDR3 Memory Controller " ?
    http://www.amd.com/uk/products/desktop/processors/amdfx/Pages/amdfx-model-number-comparison.aspx

    HyperTransport™ Technology up to 4000MT/s full duplex, or up to 16.0GB/s I/O Bandwidth
    Integrated DDR3 Memory Controller Yes
    Memory Controller Width
    128-bit
    Type of Memory Supported Up to DDR3 18661
    Memory Bandwidth Up to 21 GB/s dual channel memory bandwidth
    Total Processor-to-system Bandwidth (HyperTransport plus memory bandwidth) Up to 37 GB/s
    Process Technology 32 nanometer, SOI (silicon-on-insulator) Technology
    Packaging AM3+
    Thermal Design Power 220W, 125W, & 95W
    Manufacturing Sites GLOBALFOUNDRIES Dresden, Germany
    For the latest performance benchmarks and detailed technical documentation of the AMD FX Processor, please visit Benchmarks and Technical Documentation.
    1866 supported with 1 DPC (DIMM per Channel) in single memory slot motherboard designs
  8. FX8350 will run the 1866.
  9. SharperZeroCool said:
    From what you said yes, the CPU will only support the speed of 1866MHZ while in a dual channel config, if you use a quad channel config it will turn the memory down to 1600MHZ

    Your link isn't working for me.

    While the memory would operate at 1600MHZ it would also probably operate at a lower timing but you would probably be better of going with a 1600MHZ memory since its cheaper. Going faster on memories is not always helpful since the timing also goes up, the best bet is to find the memory that has the lowest timing for the frequency that fits your hardware.

    For 1600MHZ memories the lowest timings i came to find was 7-8-7-24 but recently the best i got when i updated my system was 9-9-9-24

    ____________________________

    NO, it will all depend on the CPU itself, the CPU's are rated up to 1866 at 1 stick per channel, some can run 4 sticks of 1866 - but contrary to what's being said here - that is NOT in quad channel - AMD doesn't support QUAD channel the Intel X79 chipset on the 2011 are the only mainstream mobos that do, if you run four sticks it's still only dual channel. And NO, it doesn't automatically drop you to 1600...either it will run or it will result in an OC failed and go to the mobos default of 1066 or 1333.
    Also, with AMD it's best not to spend alot on high end low CL DRAM as they have weak (relatively speaking) MCs (memory controllers), the MC of the FX CPUs is actually 1333 acording to their own BIOS and Kernel Programming Guide - they artificially OCed the CPU in order for it to be able to run 1866 at 1 stick per channel and that's why when you fully populate you are often stuck with running 1333 or 1600
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