Amazing SLI Scaling: Do Two GeForce GTX 460s Beat One GTX 480?

Power, Efficiency, And Heat

Power consumption numbers are measured for the entire system by a meter gauging use from the wall outlet. Our OCZ-Z1000 power supply is 90% efficient (±1%) at the “Full GPU Load” power consumption levels charted below. So, anyone who wants to know the actual consumption of system components need only multiply the “Full GPU Load” readings by 0.9.

Efficiency is a comparison of work done to energy used. There is no metric to determine 100% efficiency using bits-per-watt or even FPS-per-watt, since bits and rendered frames are intangible. The best we can hope for is a comparison of how much more or less efficient one system is compared to another. To do that, we must first see how much more energy each system used than the lowest-consuming system, which in this case is the single GeForce GTX 460-based configuration.

Next, we need to know how much more performance the three top systems have over the fourth. We averaged the frames per second of each system and divided the result by that of the lowest system.

Dividing the performance difference (above) by the power consumption difference (two charts above) gives us a “full load” performance-per-watt difference, with the lowest system representing 100%. On the other hand, since the work produced by idle systems is invariable, comparing the efficiency of idle systems requires simply dividing each configuration’s idle power by that of the most miserly configuration. Because there is no such thing as 100%-efficient, subtracting the 100% baseline from each result allows us to show the difference between configurations.

Adding a second GeForce GTX 460 gives us a 90% performance boost, while requiring only 53% more total system power, yielding a performance-per-watt increase of 24% (1.90 / 1.53). The same system, at idle, consumes 13.1% more power than the single GeForce GTX 460 baseline.

And now for heat:

The temperature numbers above are for the first card in the system. In our SLI configuration, with two cards spaced less than one expansion slot apart, the bottom card actually runs cooler than a single card. The is likely due to the system increasing the speed of both fans simultaneously. Our motherboard also supports spreading the cards several spaces apart, and a test with two spaces between cards revealed identical temperatures in SLI and single-card configurations.

Thomas Soderstrom
Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware US. He tests and reviews cases, cooling, memory and motherboards.
  • welshmousepk
    I had given up on Nvidia this gen, but somehow they have pulled off the impossible.

    I'm seriously considering picking up two of these...
  • Lmeow
    Wow. GTX 460 SLIs smoked the GTX 480 the whole way through... (you'd really think it'd be the other way - seeing as those GTX 480s don't exactly run 'cool' :D) without breaking a sweat.

    The only reason to get a GTX 480 now is if your motherboard doesn't have dual PCI-E x16 slots/support SLI or you want to SLI GTX 480s later on.

    Good job nVidia - real comeback.
  • lutel
    To buy or not to buy GTX 460 - that is the question which will be easier if you give decent review of GTX 460 boards, with one 5850 focused on noise (take a look at silentpcreview methodology) and overclocability.
  • scrumworks
    welshmousepkI had given up on Nvidia this gen, but somehow they have pulled off the impossible. I'm seriously considering picking up two of these...
    Or you can wait couple of months for Southern Islands that makes everything nvidia has look dated.
  • "With an MSRP of $250 and a Web price around $230, the GeForce GTX 460 was already known to be a great mid-priced performer"

    Is that Canadian pricing I see, because in America GTX 460s go for $199!.

    For $250 you get a GTX 460 factory overclocked from 675 mhz to 800MHZ! and with 1GB of ram, not 768mb! 2 of which are 90% as fast as a Ati 5970, for $200 less!
  • Maziar
    Great review.
    I am amazed by the 90% performance boost over a single GTX 460.
    Although it has more power consumption than 1 GTX 480,but its a great cost-effective option for those who can't afford the 480 but need similar(or better) performance
  • andrewcutter
    scrumworksOr you can wait couple of months for Southern Islands that makes everything nvidia has look wait is a continous exercise you can only look at now at the time of buying...:D
  • hardcore_gamer
    great article..gotta love toms :D
  • andrewcutter
    I might be mistaken but is this sparkle card a bit more power hungry. the power requirement seems to be a bit high for 460.:(
  • dragonfang18
    But you lose the power to upgrade... At least I can still save up for another 480 down the road when I need an upgrade.