Efficiency Gets Another Boon: Parallel Kernel Support

In GPU programming, a kernel is the function or small program running across the GPU hardware. Kernels are parallel in nature and perform the same task(s) on a very large dataset.

Typically, companies like NVIDIA don't disclose their hardware limitations until a developer bumps into one of them. In GT200/G80, the entire chip could only be working on one kernel at a time.

When dealing with graphics this isn't usually a problem. There are millions of pixels to render. The problem is wider than the machine. But as you start to do more general purpose computing, not all kernels are going to be wide enough to fill the entire machine. If a single kernel couldn't fill every SM with threads/instructions, then those SMs just went idle. That's bad.


GT200 (left) vs. Fermi (right)

Fermi, once again, fixes this. Fermi's global dispatch logic can now issue multiple kernels in parallel to the entire system. At more than twice the size of GT200, the likelihood of idle SMs went up tremendously. NVIDIA needs to be able to dispatch multiple kernels in parallel to keep Fermi fed.

Application switch time (moving between GPU and CUDA mode) is also much faster on Fermi. NVIDIA says the transition is now 10x faster than GT200, and fast enough to be performed multiple times within a single frame. This is very important for implementing more elaborate GPU accelerated physics (or PhysX, great ;)…).

The connections to the outside world have also been improved. Fermi now supports parallel transfers to/from the CPU. Previously CPU->GPU and GPU->CPU transfers had to happen serially.

A More Efficient Architecture ECC, Unified 64-bit Addressing and New ISA
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  • bigboxes - Saturday, October 3, 2009 - link

    RED ROOSTER! jk :p

    FWIW, I'm glad AT banned that fool. Too bad it took 37 pages of fanboi ranting for it to come to fruition. For those that cry that there is no place to discuss this AT does have a video forum that will not allow this kind of shenanigans. Does anyone wonder if this is Rollo back from the grave?
    Reply
  • palladium - Monday, October 5, 2009 - link

    Not quite:

    http://www.dailytech.com/article.aspx?newsid=16410">http://www.dailytech.com/article.aspx?newsid=16410

    Scroll down halfway thru the comments. He re-registered as SilicconDoc and barks about his hatred for red roosters (in an Apple-related article!)
    Reply
  • johnsonx - Monday, October 5, 2009 - link

    that looks more like someone mocking him Reply
  • - Sunday, October 4, 2009 - link

    According to this very link http://www.anandtech.com/video/showdoc.aspx?i=3573...">http://www.anandtech.com/video/showdoc.aspx?i=3573... AMD already presented a WORKING SILICON at Computex roughly 4 months ago on June 3rd. So it took roughly 4 and a half months to prepare drivers, infrastructure and mass production to have enoough for the start of Windows 7 and DX11. However, Nvidia wasnt even talking about W7 and DX11 so late Q1 2010 or even later becomes more realistic than december. But there are much more questions ahead: What pricepoint, Clockrates and TDP. My impression is that Nvidia has no clue about this questions and the more I watch this development, the more Fermi resembles to the Voodoo5 Chip and the V6000 card which never made into the market because of its much to high TDP. Reply
  • silverblue - Sunday, October 4, 2009 - link

    Nah, I expect nVidia to do everything they can to get this into retail channels because it's the culmination of a lot of hard work. I also expect it to be a monster, but I'm still curious as to how they're going to sort out mainstream options due to their top-down philosophy.

    That's not to say ATI's idea of a mid-range card that scales up and down doesn't have its flaws, but with both the 4800 and 5800 series, there's been a card out at the start with a bona fide GPU with nothing disabled (4850, and now 5870), along with a cheaper counterpart with slower RAM and a slightly handicapped core (4830/5850). Higher spec single GPU versions will most likely just benefit from more and/or faster RAM and/or a higher core clock, but the architecture of the core itself will probably be unchanged - can nVidia afford to release a competing version of Fermi without disabling parts of the core? If it's as powerful as we're lead to believe, it will certainly warrant a higher price tag than the 5870.
    Reply
  • Ahmed0 - Saturday, October 3, 2009 - link

    Nvidia wants it to be the jack of all trades. However, they are risking with being an overpriced master of none. Thats probably the reason they give their cards more and more gimmicks to play with each year. They are hoping that the cards value will be greater than the sum of its parts. And that might even be a successful strategy to some extent. In a consumerist world, reputation is everything.

    They might start overdoing it at some point though.

    Its like mobile phones nowadays. You really dont need to have a radio, an mp3-player, a camera nor other such extras in it (in fact, my phone isnt able to do anything but call and send messages). But unless you have these features, you arent considered as competition. It gives you the opportunity to call your product "vastly superior" even though from a usability standpoint it isnt.
    Reply
  • SymphonyX7 - Saturday, October 3, 2009 - link

    Ahh... I see where you're coming from. I've had many classmates who've asked me what laptop to buy and they're always so giddy when they see laptops with the "Geforce" sticker and say they want it cause they want some casual gaming. Yes, even if the GPU is a Geforce 9100M. I recommended them laptop using AMD's Puma platform and many of them ask if that's a good choice (unfortunately here, only the Macbook has a 9400M GPU and it's still outside many of my classmates' budgets). Seems like brand awareness of Nvidia amongst many consumers is still much better than AMD/ATI's. So it's an issue of clever branding then?

    Reply
  • Lifted - Saturday, October 3, 2009 - link

    A little late for any meaningful discussion over here as AT let the trolls go for 40 or so pages. I doubt many people can be arsed to sort through it now, so you'd be better off going to a forum for a real discussion of Fermi. Reply
  • neomocos - Saturday, October 3, 2009 - link

    if you missed it then here you go ... happy day for all of us :

    quote from comment posted on page 37 by Pastuch

    " Below is an email I got from Anand. Thanks so much for this wonderful site.

    -------------------------------------------------------------------
    Thank you for your email. SiliconDoc has been banned and we're accelerating the rollout of our new comments rating/reporting system as a result of him and a few other bad apples lately.

    A- "
    Reply
  • james jwb - Saturday, October 3, 2009 - link

    Some may enjoy it, but this unusual freedom that blatant trolls using aggressive, rude language are getting lately is making a mockery of this site.

    I don't mind it going on for a while, even 20 pages tbh, it is funny, but at some point i'd like to see a message from Gary saying, "K, SiliconDoc, we've laughed enough at your drivel, tchau, banned! :)"

    That's what i want to see after reading through 380 bloody comments, not that he's pretty much gotten away with it. And if he has finally been banned, i'd actually love to know about it in the comments section.

    /Rant over.
    Reply

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