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AMD Radeon HD 8790M: Next-Gen Mobile Mainstream Graphics Preview

AMD Radeon HD 8790M: Next-Gen Mobile Mainstream Graphics Preview
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AMD sent over some of its lab gear: an interposer card and two PCI Express-based boards with MXM modules...one of which hosted its upcoming Radeon HD 8790M GPU. At long last, the GCN architecture is hitting mainstream notebooks in its 28 nm glory.

Here we were just saying not to expect AMD Radeon HD 8000-series graphics cards until later in 2013 in Best Graphics Cards For The Money: December 2012, and the company sends over its Radeon HD 8790M. Cool, right? We haven't even reviewed a desktop-based 8000-series card yet.

Well, not so fast. AMD does currently offer mobile graphics processors based on its Graphics Core Next architecture. However, those are limited to the high-end of its Radeon HD 7700, 7800, and 7900 families. Everything in the 7600-series and lower centers on the company's VLIW5 shader configuration, which you last saw make news on the desktop when it launched the Radeon HD 6800 series in October of 2010. So, yeah. It's high time that AMD starts nudging the far superior GCN architecture and 28 nm manufacturing into mainstream and entry-level mobile designs.

Enter the Radeon HD 8000M-series chips.

What's up with the name, then? Call it carry-over inflation from the Radeon HD 7000M line-up, which also mixed multiple architectures. The take-away, right up front, is that even though we're previewing a Radeon HD 8790M, this isn't the 8000-series you're expecting on the desktop. Rather, it's AMD's effort to get GCN into the mobile space, an exciting-enough prospect in its own right, given that small, lightweight notebooks stand to gain quite a bit from an energy-efficient design able to bolster performance significantly.

We're not particularly happy about the model confusion, as we've pointed out many times in the past. But AMD didn't leave itself much room to roll out GCN-enabled Radeon HD 7000M-series parts. And besides, Windows 8 is here. OEMs want to see shiny new names to go along with their latest models. 

Those marketing shenanigans don't diminish AMD's claim that the Radeon HD 8000Ms are going to be quite a bit faster than the VLIW5-based GPUs they replace. On the desktop, we saw the Radeon HD 7000-series add-in cards not only improve performance appreciably, but the GCN architecture also helped ratchet up efficiency and improve the company's standing in more general-purpose compute workloads. Equally impressive were the speed-ups AMD's driver team managed to coax from GCN after the architecture's introduction. We expect that GCN-enabled mobile parts to wield the same benefits, plus enjoy a more mature driver (including a fixed implementation of its switchable Enduro technology, which was recently patched to address a frame rate-limiting bug).

AMD's Mainstream Radeon HD 8000M-Series

AMD Notebook Graphics Line-Up In Q1'13

Radeon HD 8500M
Radeon HD 8600M
Radeon HD 8700M
Radeon HD 8800M
Radeon HD 7800M
Radeon HD 7900M
Stream Processors
384
384
384
640
640
1280
Engine Clock
Up to 650 MHz
Up to 775 MHz
Up to 850 MHz
Up to 700 MHz
Up to 800 MHz
850 MHz
Memory Clock
Up to 1125 MHz (GDDR)
Up to 1000 MHz (DDR3)
Up to 1125 MHz (GDDR)
Up to 1000 MHz (DDR3)
Up to 1125 MHz (GDDR)
Up to 1000 MHz (DDR3)
Up to 1125 MHz (GDDR)
Up to 1000 MHz (GDDR5)
1000 MHz (GDDR5)
Single-Precision Compute
537 GFLOPS
633 GFLOPS
Up to 691 GFLOPS
Up to 992 GFLOPS
Up to 1024 GFLOPS
2176 GFLOPS
Double-Precision Compute
33 GFLOPS
39 GFLOPS
Up to 42 GFLOPS
62 GFLOPS


Code Name
Mars
Mars
Mars
Venus
Heathrow
Wimbledon


As you can see, the Radeon HD 8000Ms actually slot in underneath AMD's Radeon HD 7800M-series in the Q1 product line-up. AMD plans to fix this in Q2, when 7800M- and 7900M-series replacements get the entire portfolio into the Radeon HD 8000M family.

If you've heard rumors about the Venus and Mars parts, and thought they had something to do with the desktop, then you'll be surprised to learn that those are the code names for two mobile GPUs. Venus is one component, while Mars is divided into three families, all equipped with 384 Stream processors, but operating at different clock rates. 

AMD does plan to turn features on and off to differentiate its new GPUs, too. For example, the Mars-based Radeon HD 8790M we're previewing does not include support for the company's Video Codec Engine (VCE). Conversely, the Radeon HD 8800Ms, armed with Venus, are expected to include VCE functionality to speed up video encoding and decoding in hardware.

Previewing GCN For The Mainstream: Radeon HD 8790M, Benchmarked

While we would have loved to start by taking a look at one of AMD's Radeon HD 8800M GPUs, the Radeon HD 8790M is its first mainstream GCN-based graphics processor ready for testing. In fact, the company hasn't even started announcing OEM design wins yet. 

You'd think that would make it hard to benchmark the Radeon HD 8790M. However, we have a bit of hardware in the lab that should allow us to draw a comparison between AMD's next-generation mobile line-up and the one it replaces. The interposer card in the image below drops into a PCI Express x16 slot, and accommodates an MXM module. AMD and Nvidia use these things in their own labs during the bring-up process. They make it possible to do all of the testing needed before an OEM integrates a GPU into its own notebook design. 

The interposer solves some problems, even as it introduces others. Let's start with its advantages.

First, and perhaps most important for the scientifically-minded out there, it allows us to maintain a common test platform. Were we to instead benchmark notebooks from competing vendors against each other, we'd have to take different processors, thermal limits, clock rates, memory capacities, and motherboards into consideration. This way, the only things changing are the MXM modules. Moreover, getting our hands on these components allows us to test weeks or months before OEM notebooks start shipping. 

Conversely, we're painfully aware that dropping mobile hardware into a desktop environment ignores many of the constraints OEMs face when it comes to integration. We don't get a sense for thermal output or battery consumption during a 3D workload. That makes it easy to create an unrepresentative comparison. See the heat sink on the 8790M? It's quite a bit larger than the 7670M's cooling solution. Could we be facing a match up that never pans out in the real-world? Perhaps, though a 28 nm processor and proven-better efficiency give the GCN-based part headroom that the prior-gen part doesn't enjoy. When we first started this evaluation, AMD told us we were working with a Radeon HD 8770M, and that it was as close to a drop-in replacement for the 7670M as you'd find, matching its TDP. But after GPU-Z indicated that we were dealing with a Radeon HD 8790M, the company corrected itself and confirmed the higher-end part, operating at 850 MHz with a 900 MHz boost state available. 

There's no way for us to be certain that the previous-gen part, the part we originally thought we'd be testing, and the 8790M we actually have in the lab would all work in the same notebook, or if their respective thermal and power attributes would preclude one or more from sharing compatibility. So, we're hedging our bets by not involving Nvidia in this discussion, and recommending that you consider the performance we're presenting as a comparison between two distinct models in AMD's line-up, which you wouldn't necessarily find in the same chassis.

The specs on the Radeon HD 7670M match what we are expecting. GPU-Z doesn't fully recognize the 8790M, but it does pick up its maximum 900 MHz boost clock.

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Top Comments
  • 30 Hide
    acku , December 21, 2012 4:21 AM
    mayankleoboy1Nice preview, Aku and AMD.Though i suspect you and Chris already have large 'hints' about the HD8000 series performance, but under NDA.


    In the words of Sgt. Schultz "I know nothing." =_=

    Cheers,
    Andrew Ku
    Tom's Hardware
  • 22 Hide
    shikamaru31789 , December 21, 2012 3:41 AM
    Wow, can't say I expected to see any 8000 series/700 series benchmarks for at least a few months. Looks prettyimpressive for a mobile GPU, can't wait to see what the high end mobile and desktop cards can do.
  • 18 Hide
    mayankleoboy1 , December 21, 2012 3:45 AM
    Nice preview, Aku and AMD.

    Though i suspect you and Chris already have large 'hints' about the HD8000 series performance, but under NDA.
Other Comments
  • 22 Hide
    shikamaru31789 , December 21, 2012 3:41 AM
    Wow, can't say I expected to see any 8000 series/700 series benchmarks for at least a few months. Looks prettyimpressive for a mobile GPU, can't wait to see what the high end mobile and desktop cards can do.
  • 1 Hide
    A Bad Day , December 21, 2012 3:42 AM
    Sometimes I wonder why instead of CFing or SLIing two high end mobile GPUs, a desktop GPU would've achieved the same performance but without the stuttering or driver issues.

    And if thermal management is an issue, then the desktop GPUs could always be undervolted (but of course more expensive because of the extra step).
  • 15 Hide
    A Bad Day , December 21, 2012 3:44 AM
    Also, I'm interested to see if the MxM cards of the 8000s are available for retail purchase. I'd like to buy a 15" laptop that supports MxM and is on sale, and swap out the weak GPU.
  • 10 Hide
    Novuake , December 21, 2012 3:44 AM
    Second review I have seen that uses this module method. Interesting way of doing it. Thanks Toms and AMD.
  • 18 Hide
    mayankleoboy1 , December 21, 2012 3:45 AM
    Nice preview, Aku and AMD.

    Though i suspect you and Chris already have large 'hints' about the HD8000 series performance, but under NDA.
  • 1 Hide
    SteelCity1981 , December 21, 2012 3:52 AM
    looks like the value brand hit the end of the line with the 7000m series and id expect that with the APU's becoming the standard now for value graphics.
  • 30 Hide
    acku , December 21, 2012 4:21 AM
    mayankleoboy1Nice preview, Aku and AMD.Though i suspect you and Chris already have large 'hints' about the HD8000 series performance, but under NDA.


    In the words of Sgt. Schultz "I know nothing." =_=

    Cheers,
    Andrew Ku
    Tom's Hardware
  • 12 Hide
    amuffin , December 21, 2012 4:42 AM
    ackuIn the words of Sgt. Schultz "I know nothing." =_=Cheers,Andrew KuTom's Hardware


    That's what they all say! ;) 
  • 2 Hide
    Robert Pankiw , December 21, 2012 4:47 AM
    A Bad DaySometimes I wonder why instead of CFing or SLIing two high end mobile GPUs, a desktop GPU would've achieved the same performance but without the stuttering or driver issues. And if thermal management is an issue, then the desktop GPUs could always be undervolted (but of course more expensive because of the extra step).


    If you look, there is only one chip (shown on this page) which means it is not being CrossFired. I agree that 8780M would be a better name than 8790M. Andrew Ku, maybe on the front page you can clarify this?

    About using desktop parts, it is my understanding that they sometimes do exactly that. Take the 7970M, which as far as I can tell, is an 78XX part (I forget which one) except the mobile chip has MUCH higher binning than the desktop 78XX.
  • -4 Hide
    A Bad Day , December 21, 2012 5:33 AM
    If the 7970M uses two 78XX, why not use a highly binned and undervolted 79XX? Again, better driver stability, more supports from games, more consistent performance scaling, and less micro-stuttering.
  • 5 Hide
    acku , December 21, 2012 5:55 AM
    Yeah. There's no CrossFire here.
  • 7 Hide
    silverblue , December 21, 2012 5:56 AM
    Interesting to see a relatively detailed preview this far ahead of launch. AMD should be doing this more - thanks to both parties. I was wondering - why not connect a power meter up and test the desktop setup? Would it be too prone to variation?
  • 8 Hide
    acku , December 21, 2012 6:01 AM
    Cause it's not even final silicon. And power is always going to be a function of that and shipping clock speeds, which we don't know yet.
  • 5 Hide
    silverblue , December 21, 2012 6:03 AM
    Very true. Just curious, though. :) 
  • 9 Hide
    acku , December 21, 2012 6:09 AM
    silverblueVery true. Just curious, though.

    Hell I wanted to show numbers, but I think it would be premature and possibly misleading.
  • 3 Hide
    mayankleoboy1 , December 21, 2012 6:13 AM
    So how does this chip compare to GT3 of Haswell ? :whistle: 
  • 2 Hide
    silverblue , December 21, 2012 6:14 AM
    Now, now... :D 
  • 7 Hide
    ojas , December 21, 2012 6:36 AM
    mayankleoboy1Nice preview, Aku and AMD.Though i suspect you and Chris already have large 'hints' about the HD8000 series performance, but under NDA.

    They even have Haswell chips floating around their office(s), I just know it :D 
  • 5 Hide
    ojas , December 21, 2012 6:42 AM
    BTW good call using Hitman, hope we see it more often.

    Not because it's an ohmygodbestgameever type of game (has a few issues), but it is good for performance benchmarking.
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