Become a fan of Slashdot on Facebook


Forgot your password?
AMD Graphics Hardware

New GPU Testing Methodology Puts Multi-GPU Solutions In Question 112

Vigile writes "A big shift in the way graphics cards and gaming performance are tested has been occurring over the last few months, with many review sites now using frame times rather than just average frame rates to compare products. Another unique testing methodology called Frame Rating has been started by PC Perspective that uses video capture equipment capable of recording uncompressed high resolution output direct from the graphics card, a colored bar overlay system and post-processing on that recorded video to evaluate performance as it is seen by the end user. The benefit is that there is literally no software interference between the data points and what the user sees, making it is as close to an 'experience metric' as any developed. Interestingly, multi-GPU solutions like SLI and CrossFire have very different results when viewed in this light, with AMD's offering clearly presenting a poorer, and more stuttery, animation."
This discussion has been archived. No new comments can be posted.

New GPU Testing Methodology Puts Multi-GPU Solutions In Question

Comments Filter:
  • by amanicdroid ( 1822516 ) on Friday February 22, 2013 @04:28PM (#42983735)
    This is the explanation I've been given for the disparity between Nvidia and AMD: []


    Secondly, another difference favoring Bitcoin mining on AMD GPUs instead of Nvidia's is that the mining algorithm is based on SHA-256, which makes heavy use of the 32-bit integer right rotate operation. This operation can be implemented as a single hardware instruction on AMD GPUs (BIT_ALIGN_INT), but requires three separate hardware instructions to be emulated on Nvidia GPUs (2 shifts + 1 add). This alone gives AMD another 1.7x performance advantage (~1900 instructions instead of ~3250 to execute the SHA-256 compression function).

    For GPU programming I've enjoyed Nvidia's CUDA package greatly over wrangling OpenCL that Radeon relies on.

  • by pclminion ( 145572 ) on Friday February 22, 2013 @05:23PM (#42984555)

    Out of curiosity, what's your break even point?

    I don't know where the break even point is, but once you pass it, you can be very profitable. One of my friends built a custom "supercomputer" out of cheap motherboards and graphics cards for about $80k -- along with completely custom software to automatically tune clock speeds and fan rates in real time (all of which was written in bash script). At peak performance, his machine generated about $20k worth of bitcoin every month, which easily paid for the $12k monthly electric bill.

    After a couple of difficulty-doublings, and the imminent arrival of the ASIC miners, this lost its profitability, and he went back to being a DBA... The machine is still out at the farm, cranking away. I think he'll disassemble it and part it out for cash in a month or two.

  • Re:Developers (Score:4, Informative)

    by mikael ( 484 ) on Friday February 22, 2013 @06:25PM (#42985301)

    Developers still like to have everything on a "main loop" - render static scenery, get user move, render player, get network player moves, render network players, render auxiliary data). Other stuff will be spinning and bobbing up and down on its own based on timers. Some frames might never be rendered, but they help keep the "tempo" or the smoothness of the animation. As each PC screen can have a different screen resolution, it will have a different refresh rate, anything from 50Hz to 120/240Hz. Every rendered frame is only going to be visibile for several milliseconds (50Hz = 20 milliseconds, 100Hz = 10 milliseconds). If a frame is rendered, it will be perceived even if not consciously.

    Early home computers allowed the program to synchronize animation updates to the VBI (Vertical Blank Interrupt) and HBI (Horizontal Blank Interrupt). That way, you could do smooth jitter-free physics synchronised to the frame flipping.

    16-bit console system programmers would render out lines across the current scan-line to see how much processing they could do in each frame. While the tiles were updated during the VBI, the physics could be updated during the CRT scanning.

    These days, I would guess you would need either a vertical blank callback for the CPU or shader for the GPU.

  • by pclminion ( 145572 ) on Friday February 22, 2013 @07:05PM (#42985725)

    Dude, it's a farm. A fucking farm. 40 acres of red wheat.

    He designed the rack system himself, along with custom power supply headers that he had fabbed at a nearby plant. He even tried to reduce equipment costs by hiring a Taiwanese company to produce custom GPU cards for him for $70 a piece (they didn't work very well).

    Nobody does that shit anymore. It was like watching Steve Wozniak.

  • by pclminion ( 145572 ) on Friday February 22, 2013 @08:02PM (#42986213)

    It makes me sad that someone could run up a $12K monthly electric bill without assigning an environmental cost to where that power was coming from.

    Making assumptions is bad.

    Before the Bitcoin operation got started, my friend's business was making biodiesel out of local rendered chicken fat and other things. He single-handedly supplied most of the farmers in a 5 mile radius with fuel for their farm operations. Prior to the biodiesel years, he ran the largest privately owned solar grid in the county, providing something like 25 kilowatts back to the grid, for a couple of years solid. He is the most environmentally obsessed person I know, and has certainly contributed far more to the local green economy than he has taken out of it.

    The ultimate plan, which did not come to fruition (because of the rising difficulty of mining bitcoin, as I stated earlier), was to completely cover the 40 acre property with an array of solar panels, each panel having a custom GPU mining module installed on the underside -- open air cooling of the machines, solar power for the bitcoins, and it would have qualified as the largest solar array in the United States.

    To think that he's some kind of forest-destroying air-blackening capitalist is about the furthest from the truth as you can get. Check your assumptions.

A committee is a group that keeps the minutes and loses hours. -- Milton Berle