AMD RADEON RX VEGA 56 & 64

It’s been a long time com­ing, so is AMD’s new Vega graph­ics tech ahead of its time, or just late to the party? Jarred Wal­ton finds out.

APC Australia - - Contents - mem­ory “Vega in­cludes in two 8GB stacks. of HBM2 Th­ese de­liver the same 512GB/s band­width as the four stacks of HBM1 in last-gen’s Fiji, but with two stacks, the sil­i­con in­ter­poser doesn’t need to be as large, and HBM2 den­si­ties have al­lowed AMD to dou­ble

Let’s be frank: the Vega 56 and 64 are what we wanted to see last year, right around the time AMD was busy launch­ing Po­laris for the main­stream mar­ket. But Vega wasn’t even close to be­ing ready. So why did it take so long for AMD to get a high-end re­place­ment for Fiji and the R9 Fury X out the door? AMD has talked about nu­mer­ous ar­chi­tec­tural up­dates that have been made with Vega, and in the pro­fes­sional world, some of th­ese could be mas­sively use­ful, but as we’re APC, we’re at least equally in­ter­ested in how th­ese new cards stack up as a gam­ing de­vice. So does it?

RX VEGA 64

Let’s quickly talk specs. Vega in­cludes 8GB of HBM2 mem­ory in two stacks, which de­liver the same 512GB/s band­width as the four stacks of HBM1 in last-gen’s Fiji, but with just two stacks, the sil­i­con in­ter­poser doesn’t need to be as large, and HBM2 den­si­ties have al­lowed AMD to dou­ble the amount of mem­ory. But AMD isn’t just call­ing this HBM or VRAM; it’s now a High-Band­width Cache (HBC) and there’s also a new High-Band­width Cache Con­troller (HBCC). The dif­fer­ence is im­por­tant, be­cause the HBCC plays a much more prom­i­nent role in mem­ory ac­cesses. AMD calls this a “com­pletely new mem­ory hi­er­ar­chy”. That’s prob­a­bly a bit of hy­per­bole, but the idea is to bet­ter en­able the GPU to work with large data sets, which is be­com­ing an in­creas­ingly dif­fi­cult prob­lem.

Vega also has a new ge­om­e­try pipe­line, with over twice the through­put per clock as AMD’s pre­vi­ous ar­chi­tec­ture. The com­pute unit has also been im­proved, with na­tive sup­port for packed FP16 op­er­a­tions, which should prove very use­ful for ma­chine learn­ing ap­pli­ca­tions. AMD has im­proved the pixel en­gine, too, with a new Draw Stream Bin­ning Ras­ter­izer that helps cull pix­els that aren’t vis­i­ble in the fi­nal scene.

We didn’t get the liq­uid­cooled Vega 64 for test­ing, but it should be up to 8% faster than the air-cooled ver­sion, based on boost clocks. If you look at the raw num­bers, Vega holds prom­ise — with higher the­o­ret­i­cal com­pu­ta­tional per­for­mance and more mem­ory band­width than the GeForce GTX 1080 Ti — but AMD’s GCN ar­chi­tec­ture has tra­di­tion­ally trailed be­hind Nvidia GPUs with sim­i­lar TFLOPS. DirectX 12 games, mean­while, tend to track a bit closer to the the­o­ret­i­cal per­for­mance, and cer­tain tasks (like cryp­tocur­rency min­ing) can do very well on AMD ar­chi­tec­tures. But the power re­quire­ments of AMD GPUs have tra­di­tion­ally been higher than the Nvidia equiv­a­lents, and that re­mains true with Vega.

TAK­ING ON NVIDIA’S BEST?

Many in the gam­ing world were hop­ing Vega would be able to take down the heavy­weight cham­pion, the GTX 1080 Ti. In test­ing, how­ever, that didn’t hap­pen, as the 1080 Ti re­mains out of reach, though to be fair, it also re­mains in a higher priced bracket. Based on cost alone, the di­rect com­pe­ti­tion for the Vega 64 is Nvidia’s GTX 1080, while the Vega 56 is look­ing to take on the GTX 1070.

Vega 64 runs games fine — more than fine, as it’s now the third-fastest con­sumer graph­ics card, and we’d

ex­pect noth­ing less for $800. At best, Vega 64 is just a hair faster than the GTX 1080, but at worst, it can be about 30% slower — on av­er­age, the GTX 1080 leads by just un­der 10%.

The Vega 64 re­ally feels like a one-gen­er­a­tion up­grade, de­spite the fact that AMD skipped up­dates to the high-end mar­ket last year. We of­ten rec­om­mend skip­ping a gen­er­a­tion or two of hard­ware be­tween up­grades, which means up­grad­ing ev­ery 2–3 years on graph­ics cards. Each gen­er­a­tion will typ­i­cally im­prove per­for­mance by 30% or so, and that’s not usu­ally enough to war­rant an up­grade for most gamers. If you skip a gen­er­a­tion, you po­ten­tially end up with a 60–70% per­for­mance jump. If you’re al­ready run­ning a higher-end AMD card from last gen­er­a­tion (like an RX 570 or RX 580), then our rec­om­men­da­tion to wait an­other round still stands.

What about power use? While it’s a wash at idle, while gam­ing, the Vega 64 con­tin­ues AMD’s trend, us­ing 478W at the out­let on the test sys­tem com­pared to 370W for the GTX 1080.

RX VEGA 56

Vega 64 was clearly de­signed to go af­ter Nvidia’s top parts. It came up short of the 1080 Ti, but is rel­a­tively close to the 1080. The Vega 56 doesn’t aim quite as high or cost as much, so is it a bet­ter bet? While the power draw is still a bit high on this slightly lower-end card (as we mea­sured 400W while play­ing games, com­pared to 314W for the GTX 1070), look­ing at just the Vega chips, the Vega 64 is only about 9% faster than the 56 over­all, but it uses around 80W (20%) more

power. In terms of sys­tem per­for­mance per watt, the Vega 56 is, there­fore, 10% bet­ter than the Vega 64, and if we look just at the graph­ics card, it’s around 25% bet­ter.

AMD has in­cluded a BIOS switch along with a pow­er­sav­ing pro­file — but that comes at the cost of per­for­mance, of course. And if you want to over­clock it, you still can, though that will af­fect the over­all ef­fi­ciency in the re­verse di­rec­tion.

OVERCLOCKING PER­FOR­MANCE

We per­formed some pre­lim­i­nary overclocking, and things are far more in­ter­est­ing on the Vega 56 card than the 64, as you’d ex­pect. Sim­ply rais­ing the HBM2 clock­speed to a 930MHz base (close to the same as the Vega 64’s 945MHz) and crank­ing the power limit to 50% im­proved per­for­mance to where Vega 56 is ef­fec­tively tied with the 64. Go­ing fur­ther, we toyed with the per­cent­age over­clock slider and man­aged to push it up 20% higher. In both cases, sys­tem power draw while gam­ing ba­si­cally matched the Vega 64 — 480W at the out­let. But in limited test­ing, all that added clock­speed ac­tu­ally did very lit­tle for per­for­mance.

The Vega 56 isn’t just more ef­fi­cient than the Vega 64, though — when stock lev­els sta­bilise (at the time of writ­ing, it was com­pletely sold out world­wide), it should end up be­ing a lit­tle cheaper than the GTX 1070, while de­liv­er­ing nearly the same per­for­mance over­all.

The 56 ends up be­ing a good al­ter­na­tive to the GTX 1070, and an even bet­ter one if it’s ac­tu­ally read­ily avail­able at $550–$600, con­sid­er­ing the 1070 cur­rently goes for $600– $650 or more due to min­ing de­mand.

STOCK PROB­LEMS

Given the short­ages on AMD’s RX 570/580 cards, which are typ­i­cally sell­ing at prices 50% or more above the MSRP, many have feared — and miners have hoped — that the RX Vega would be an­other ex­cel­lent min­ing op­tion. In Ethereum min­ing, so far, it’s been pretty lack­lus­tre, how­ever, con­sid­er­ing the price and power use. The Vega 56 man­ages around 31MH/s and the 64 does 33MH/s. Overclocking the VRAM helps boost both cards closer to 40MH/s, so at launch, that’s not su­per promis­ing.

Part of the prob­lem is that most of the min­ing soft­ware (whether for Ethereum, Zcash or some other coin) has been finely tuned to run on AMD’s ex­ist­ing Po­laris ar­chi­tec­ture. Given time, we could see sub­stan­tially higher hashrates out of Vega, and there are ru­mours that the right com­bi­na­tion of VBIOS, driv­ers and min­ing soft­ware can hit min­ing speeds more than dou­ble what we mea­sured. All we can do is hold our breath and hope that min­ing doesn’t drive prices of Vega into the strato­sphere in the fu­ture.

Con­sid­er­ing the sig­nif­i­cantly higher clock­speeds, we had hoped Vega would per­form far bet­ter than what we’re see­ing to­day. It’s not a bad GPU by any means, but it’s not go­ing to de­throne Nvidia, at least not right now. What Vega does have go­ing for it are rea­son­able prices, and AMD users will cer­tainly ap­pre­ci­ate hav­ing some­thing that’s clearly faster than both the RX 580 and the R9 Fury X. The real tar­get would be gamers who are still run­ning R9 290/290X (or older) hard­ware.

“The Vega 56 ends up be­ing a good al­ter­na­tive to the GTX 1070, and an even bet­ter one if it’s ac­tu­ally read­ily avail­able at $550–$600.”

GRAPH­ICS CARDS VEGA 56, $600; VEGA 64, $800 | WWW.AMD.COM

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