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AMD Radeon HD 6790 Review: More Mid-Range Might

AMD Radeon HD 6790 Review: More Mid-Range Might
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Hot on the heels of Nvidia's GeForce GTX 550 Ti introduction, AMD releases a card with the same MSRP and vastly superior performance. But can it also stand up to the GeForce GTX 460 768 MB? We put the new card to the test!

Today, AMD introduces its new Radeon HD 6790, a card designed to fill space between the Radeon HD 5770 and Radeon HD 6850. As such, this board's natural competition is Nvidia's GeForce GTX 460 768 MB.

The funny thing is, Nvidia recently announced that the GeForce GTX 460 768 MB is about to be discontinued. GeForce GTX 550 Ti arrived only a few weeks ago, designated as its replacement in the space between the GeForce GTS 450 and GeForce GTX 460 1 GB.

A New Card And Familiar GPU

Before we go any further, let’s have a closer look at the Radeon HD 6790’s GPU, designated Barts LE:

This graphics processor is built using a cut-down RV870 (Barts) ASIC first seen during the Radeon HD 6800-series launch. Fully featured, this graphics processor has 14 SIMD engines, each with four texture units and 16 stream processors. Each stream processor, in turn, hosts five ALUs (AMD refers to these as stream cores). 

In the Radeon HD 6790, four of the SIMD engines are disabled, resulting in a total of 40 texture units and 800 stream cores. When it comes to pixel output, the Radeon HD 6790 uses two of Barts’ four render back-ends, each containing eight full-color ROP units, adding up to 16 total. Those of you familiar with the Radeon HD 5770 may notice that this card shares the exact same number of stream cores, texture units, and ROPs.

From here, however, things get interesting. Four 64-bit memory controllers yield an aggregate 256-bit memory interface. This is unchanged from the Radeon HD 6800-series, and is twice as potent as the 128-bit memory interface on the Radeon HD 5770. Moreover, the Radeon HD 6790 sports an 840 MHz core and 1050 MHz GDDR5 memory. Once again, this is very close to the Radeon HD 5770’s 850 MHz core and 1200 MHz memory frequencies.

With all of this info in hand, it seems clear that AMD's aim with the Radeon HD 6790 was to create a Radeon HD 5770 with a 256-bit memory interface. Of course, being based on the newer Barts architecture, this card has all of the feature benefits of the Radeon HD 6800-series, including improved tessellation performance, Eyefinity enhancements, and the ability to accelerate Blu-ray 3D video over HDMI.

With these facts in mind, let’s compare the Radeon HD 6790 to the rest of the playing field:


Radeon HD
5770
Radeon HD
6790
Radeon HD
6850
GeForce GTX 460
768 MB
GeForce GTX
550 Ti
Shader Cores
800800960
336
192
Texture Units
404048
56
32
Full Color ROPs
161632
24
24
Graphics Clock
850 MHz840 MHz
775 MHz675 MHz900 MHz
Shader Clock
850 MHz840 MHz775 MHz1350 MHz1800 MHz
Memory Clock
1200 MHz1050 MHz
1000 MHz
900 MHz1025 MHz
GDDR5 Memory
1 GB1 GB1 GB768 MB1 GB
Memory Interface
128-bit
256-bit
256-bit192-bit192-bit
Memory Bandwidth
76.8 GB/s134.4 GB/s128 GB/s 86.4 GB/s98.5 GB/s
Texture Filtering Rate
34 GTex/s33.6 GTex/s37.2 GTex/s37.8 GTex/s28.8 GTex/s
Connectors
2 x DL-DVI,
1 x HDMI,
1 x DisplayPort
2 x DVI,
1 x HDMI,
2 x DisplayPort
2 x DVI,
1 x HDMI,
2 x DisplayPort
2 x DL-DVI,
1 x mini-HDMI
2 x DL-DVI,
1 x mini-HDMI
Form Factor
Dual-slotDual-slotDual-slotDual-slot
Dual-slot
Power Connectors
1 x 6-pin2 x 6-pin1 x 6-pin2 x 6-pin
1 x 6-pin
Recommended Power Supply
450 W500 W500 W450 W
400 W
Thermal Design Power
108 W150 W
127 W150 W116 W


The Radeon HD 6790's 256-bit interface demonstrates a huge memory bandwidth advantage over the Radeon HD 5770. This should manifest itself in a number of situations—most notably, when anti-aliasing is enabled. Indeed, if it weren't for the removal of half of its ROPs, the Radeon HD 6790 would be very close competitor to the Radeon HD 6850.

We know it will perform better than Radeon HD 5770, and not as fast as the Radeon HD 6850. But how will it compare to its GeForce competition?

Since the GeForce GTX 550 Ti performs similarly to the Radeon HD 5770, we expect the new Radeon HD 6790 to easily and challenge the GeForce GTX 460 768 MB. It’s interesting that both of these cards are cut-down versions of higher-end models, but crippled in somewhat different ways. The GeForce GTX 460 768 MB has the same shader core, texture unit, and clock specifications of Nvidia's 1 GB card, but with one-third fewer ROPs and a narrower memory bus. On the other hand, the Radeon HD 6790 has fewer shader cores and texture units compared to the Radeon HD 6850. But it runs at higher clocks to compensate. The main difference is that the number of ROPs are halved, from 32 to 16.

In any case, the GeForce GTX 460 768 MB offers much more interesting competition for AMD’s new card. We anticipate the benchmarks will go back and forth between these two products, depending on the game.

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  • 2 Hide
    rohitbaran , April 5, 2011 3:16 AM
    Wow. Great card for the price, considering what nVidia has for the same segement.
  • 4 Hide
    tacoslave , April 5, 2011 3:18 AM
    I think the 550ti is the most useless release this year and yes even though the 6790 card draws more power than i would like its still miles ahead of the 550 ti. As for the gtx460 768 i think it would be stupid to take it off the market its nvidia's new 8800gt and only competition for amd 6790.
  • -1 Hide
    ct1615 , April 5, 2011 4:17 AM
    nice card but what's the price? most ati 5770 are $130 out the door (that's no 6-8 week rebate checks for those of you stupid enough to count them into the price) and the GTX 460 is $150 out the door. that pretty much leaves the $140 segment to it.
  • 1 Hide
    compton , April 5, 2011 4:17 AM
    The best part of 6790 appears to be the bitchin' CF scaling, if nothing else. Depending on where prices end up, it still would be hard to recommend when a few dollars more can get you the 6850.
  • 2 Hide
    plznote , April 5, 2011 4:19 AM
    Should be a bit cheaper imo.
  • 0 Hide
    compton , April 5, 2011 4:21 AM
    I would hope that prices end up around $139 or so, without rebates. Still the 5770 and 460s are the value kings, so I'm glad to see AMD not over pricing them. nVidia could take a lesson.
  • 1 Hide
    Anonymous , April 5, 2011 4:23 AM
    error with 6970 min fps f1 game at 1920 x 1080 res
  • 0 Hide
    Trueno07 , April 5, 2011 4:33 AM
    Wow, nice card for the money, and very competitive. Good job AMD...
  • 1 Hide
    ct1615 , April 5, 2011 4:44 AM
    funny Tom's loves this card but anantech (said it came up short) and hardware secrets both said pass on it.
  • 0 Hide
    dragonsqrrl , April 5, 2011 4:46 AM
    rohitbaranWow. Great card for the price, considering what nVidia has for the same segement.

    Nvidia no longer has anything in this segment. Well, maybe the GTX460 768, but on average it's still priced above $150. The GTX550Ti underwent an expected below MSRP price drop soon after launch, and the average price is now around $130, probably where it should've been to start.
    tacoslaveI think the 550ti is the most useless release this year and yes even though the 6790 card draws more power than i would like its still miles ahead of the 550 ti. As for the gtx460 768 i think it would be stupid to take it off the market its nvidia's new 8800gt and only competition for amd 6790.

    Again the GTX550Ti doesn't directly compete with the HD6790 and has underwent a pretty significant price drop in the short time since its launch. The GTX560 is set to replace the GTX460 768 and compete directly against the HD6790 at the $150 price point.
  • 1 Hide
    bombat1994 , April 5, 2011 6:25 AM
    Nvidia fail at the mid range segment. the only good card they have released recently was the 460. the 450, 550, failed hard. this card will be good if the companies can lower the the power usage. good job ati
  • 0 Hide
    ivan_chess , April 5, 2011 6:39 AM
    On the final graph, why is the 6790 listed below the 460? According to the graph it should be above it.
  • 0 Hide
    turboflame , April 5, 2011 6:55 AM
    The HD6790 is only a good counter to the GTX 550 purely because the GTX 550 isn't worth buying either.
  • 0 Hide
    danbfree , April 5, 2011 6:57 AM
    6850's are $145-150 after rebate, $165-170 without on Tom's sponsor site, Newegg... seems like worth the extra bit more to me!
  • 0 Hide
    SteelCity1981 , April 5, 2011 7:05 AM
    The Geforce 550 Ti is an Nvidia sales gimmick too fool people into buying a next gen card that's in production.
  • 0 Hide
    memadmax , April 5, 2011 7:14 AM
    An 11 watt power difference between the Nvidia and ATI card will hardly drive me away from the ATI card given the performance difference.....
  • 0 Hide
    rolli59 , April 5, 2011 7:21 AM
    Will be a great buy after the prices settle.
  • 0 Hide
    C 64 , April 5, 2011 8:14 AM
    Nice card - I wonder will there be a passive cooled version like the 5770 has. This would definitely made me save money for an upgrade.
    Silent yet still quite powerful => BUY!
  • 0 Hide
    mattmock , April 5, 2011 8:14 AM
    "...any screen size not divisible by eight suffers a performance penalty. This is something that will likely be patched in the future."
    Considering that it has been over a month since bulletstorm was released and it is only an 8 hour game, I think it is time to change this line to
    "...any screen size not divisible by eight suffers a performance penalty. This is something that is unlikely to patched in a reasonable timeframe."
  • 0 Hide
    henydiah , April 5, 2011 8:34 AM
    i still use vga on board... i want buy it
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