System Builder Marathon, Q1 2014: The $2400 People’s Choice PC

Overclocking

At 1.32 V CPU core, ASRock’s Turbo 4.60 GHz overclocking profile provided more than enough voltage to prevent crashing on this Core i7-4770K.

Unfortunately, that high voltage also caused it to throttle within seconds of starting an eight-thread run of AVX-optimized Prime95. Experimentation showed that a minimum of 1.275 V was needed to make this core run at 46 x 100 MHz, but that this voltage still caused thermal bottlenecking within minutes of my stability tests.

Some overclockers will point out that my stress test is unrealistically tough, that thermal throttling prevents damage, and that this protection mechanism takes minutes to start under Prime95. So, it'd be unlikely to affect our benchmarks. But when I look for a stable overclock, I avoid throttle conditions altogether. I instead dropped the CPU multiplier to 45x and began looking for the lowest voltage that would keep the CPU stable at 4.5 GHz.

A 1.24 V VCore worked great, so I also dropped the ASRock 4.60 GHz profile’s 1.30 V “CPU Cache” voltage to 1.24 V.

I increased the memory subsystem from its DDR3-1866 profile to DDR3-2133, and also configured it to 1.60 V.

To achieve stability at DDR3-2133, the three primary latencies all needed to be increased by one cycle beyond XMP settings. I usually find that tRAS can also be tightened, but that wasn’t true for this combination of memory and CPU.

As with the CPU, I don’t like the idea of graphics cards that throttle down when you need full power the most. I first increased the GPU power limit to its maximum slider setting, then began bumping up GPU clock in 25 MHz increments. After finding +175 MHz unstable and +150 MHz stable, I picked a frequency that would result in a nice round number for the GPU clock. Adding 157 MHz yielded a 1020 MHz GPU base clock and a 1059 MHz typical GPU Boost frequency.

Thomas Soderstrom
Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware US. He tests and reviews cases, cooling, memory and motherboards.
  • Darkerson
    Interesting move, showing the nicest build 1st instead of last. Cant wait to see all the builds compared and see what you all come up with as the budget goes down.
    Reply
  • captain_jonno
    Looks good. Surprised only went with a 750w PSU though. Considering 2x 780 ti's and overlocking
    Reply
  • Crashman
    12951919 said:
    Looks good. Surprised only went with a 750w PSU though. Considering 2x 780 ti's and overlocking
    Yessir, two 780s and a bit of experience in part picking lead me to expect around 700W of required system power. And, it came out just a little less than 700W.

    Power supplies of greater capacity and similar reliability at this price tend to be lower-efficiency units. And we like efficiency too.

    Reply
  • YellowBee
    I dont get the "W" usage?680+237 = 917w. Not 802w as meation above?
    Reply
  • Crashman
    12952008 said:
    I dont get the "W" usage?680+237 = 917w. Not 802w as meation above?
    It's not calculated power, it's measured power for the entire system (at the power plug). No addition or subtraction was used.

    1.) Start the system, wait for all processes to load, take a measurement (Active, but idle)
    2.) Load the CPU using eight thread of AVX-optimized Prime95, take a reading (CPU Load).
    3.) Load GPUs with 3DMark 11 Test 1 in loop, take max reading as it heats up (GPU Load).
    4.) Load both applications (CPU+GPU Load).

    The "math problem" is that any program used to fully load the GPU also partly loads the CPU. So when test 4 is Prime95+3DMark, Prime95 can only use whatever CPU resources are left with 3DMark running.

    So the most accurate system power reading is with "CPU+GPU Load" applied. The system measurement for "CPU Load" still includes the power of an idle GPU. And the system power measurement for "GPU Load" still includes the amount of CPU energy it takes to run the GPU's test application.
    Reply
  • YellowBee
    12952046 said:
    12952008 said:
    I dont get the "W" usage?680+237 = 917w. Not 802w as meation above?
    It's not a calculation, it's a reading for the entire system (at the power plug). Load the CPU using eight thread of AVX-optimized Prime95, take reading one. Load GPUs with 3DMark 11 Test 1 in loop, take max reading as it heats up.

    The "math problem" is that any program used to fully load the GPU also partly loads the CPU. So when test 3 is Prime95+3DMark, Prime95 can only use whatever CPU resources are left with 3DMark running.

    So the most accurate system power reading is with "CPU+GPU Load" applied. The system measurement for "CPU Load" still includes the reading of an idle GPU. And the system power measurement for "GPU Load" still includes the amount of CPU power it takes to run the GPU.

    Very much appreciated and satisfying answer.
    Thanks Crashman :)
    Reply
  • bemused_fred
    12952008 said:
    I dont get the "W" usage?680+237 = 917w. Not 802w as meation above?
    It's not calculated power, it's measured power for the entire system (at the power plug). No addition or subtraction was used.1.) Start the system, wait for all processes to load, take a measurement (Active, but idle)2.) Load the CPU using eight thread of AVX-optimized Prime95, take a reading (CPU Load).3.) Load GPUs with 3DMark 11 Test 1 in loop, take max reading as it heats up (GPU Load).4.) Load both applications (CPU+GPU Load).The "math problem" is that any program used to fully load the GPU also partly loads the CPU. So when test 4 is Prime95+3DMark, Prime95 can only use whatever CPU resources are left with 3DMark running.So the most accurate system power reading is with "CPU+GPU Load" applied. The system measurement for "CPU Load" still includes the power of an idle GPU. And the system power measurement for "GPU Load" still includes the amount of CPU energy it takes to run the GPU's test application.
    Any chance of including these calculations in all future articles, so that we know exactly how the power graph is calculated? Ta.
    Reply
  • Crashman
    12952271 said:
    12952046 said:
    It's not calculated power, it's measured power for the entire system
    Any chance of including these calculations in all future articles, so that we know exactly how the power graph is calculated? Ta.
    Which calculations?

    Reply
  • jabuscus
    wow. such performance. many ram. they should've put in 16gb of ram for real high-end specs. ;)
    Reply
  • Versutia
    As I'm into quiet enclosures, I'd go along this route:

    http://pcpartpicker.com/p/3fuGw

    Wondering how much of a difference would non-reference cards make. Obviously, CPU cooler and RAM could be different, BR drive optional, storage drive as well.
    Reply