Power ef­fi­ciency might not have the in­stant ap­peal of su­pe­rior graph­ics and per­for­mance, but we should take it se­ri­ously, ar­gues Ben Hard­widge


ffi­ciency just isn’t sexy. I’ve watched mar­ket­ing man­agers try to talk en­thu­si­as­ti­cally about per­for­mance per watt, and it must be like try­ing to get ex­cited about loft in­su­la­tion. Bet­ter graph­ics are cool. Faster com­put­ers are cool. Even brag­ging rights are cool. But lower power consumption? It’s tough, be­cause there’s no im­me­di­ately vis­i­ble ben­e­fit.

But while ef­fi­ciency might not be the stuff of hard­ware geek fan­tasies, it’s a ma­jor fac­tor when it comes to my buy­ing de­ci­sions. While we were sort­ing out the scor­ing sys­tem for last month’s GPU Labs test, we set­tled on a 10 per cent score for ef­fi­ciency again, but I won­der if that’s enough now. There’s a gulf be­tween Nvidia and AMD’s GPUs when it comes to power ef­fi­ciency, where our test sys­tem drew 266W from the mains with a GeForce GTX 970 in­stalled at load, but that fig­ure rock­eted up to 437W with a Radeon R9 390 in place. That’s a dif­fer­ence of 171W, and it will in­crease fur­ther as you add more cards.

Ef­fi­ciency now con­cerns dif­fer­ences of hun­dreds of watts, and for very sim­i­lar per­for­mance. Aside from any con­cerns about your car­bon foot­print, that’s bad news if you’re a PC gamer. With the higher heat out­put of non-ef­fi­cient hard­ware, you’ll need more pow­er­ful and of­ten nois­ier cool­ers, as well as more air­flow in your case to help ex­pel the hot air. It also lim­its how much hard­ware you can in­stall in your case. I wouldn’t want three Radeon R9 390X cards in my sys­tem with­out some de­cent space be­tween them for air­flow.

Poor ef­fi­ciency also lim­its what board part­ners can do with hard­ware, such as making small cards with small cool­ers. What’s

Emore, it lim­its your choice of sys­tem. You could com­fort­ably build a tiny GTX 970 rig with an SFX PSU, but not with an R9 390. Then there’s the cost of elec­tric­ity, and once you get into this ter­ri­tory it stops be­ing neg­li­gi­ble, par­tic­u­larly if you use your PC for gam­ing a lot. Choos­ing an R9 380 over a GTX 970 is al­most like leav­ing an ex­tra three 60W lights on in the house while you’re gam­ing.

GPUs aren’t the only is­sue. CPUs can also eat a lot of elec­tric­ity at full whack. In­tel has nailed ef­fi­ciency with its lat­est Sky­lake kit, with CPUs such as the Core i3-6100T hav­ing a TDP of just 35W, making it ideal for our HTPC build (see p88). Like­wise, the Core i7-6700K’s TDP is only 91W, which is an amaz­ing achieve­ment com­pared with the 220W TDPs of AMD’s topend FX CPUs.

Ef­fi­ciency is AMD’s big prob­lem at the mo­ment, partly be­cause it’s still de­pend­ing on a GPU ar­chi­tec­ture that’s nearly four years old, but AMD also seems to be dis­miss­ing ef­fi­ciency as unim­por­tant. In terms of per­for­mance and fea­tures, AMD’s kit is still com­pet­i­tive, but that isn’t enough now. When I look at what hard­ware to buy, I’m also think­ing about the heat out­put and power consumption, par­tic­u­larly when the dif­fer­ences in­volve hun­dreds of watts.

For me, ef­fi­ciency is now a ma­jor fac­tor when it comes to buy­ing de­ci­sions, even if it isn’t par­tic­u­larly ex­cit­ing, but I’m of­ten told that en­thu­si­asts don’t care, and that per­for­mance and frame rates are the pri­or­i­ties. Is this true? Do PC en­thu­si­asts really not care about heat out­put and power consumption? I find it very hard to be­lieve, and I’d be in­ter­ested in your thoughts. Drop me a line at let­ters@cus­tom­pc­

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