NVIDIA's Fermi: Architected for Tesla, 3 Billion Transistors in 2010
by Anand Lal Shimpi on September 30, 2009 12:00 AM EST- Posted in
- GPUs
A More Efficient Architecture
GPUs, like CPUs, work on streams of instructions called threads. While high end CPUs work on as many as 8 complicated threads at a time, GPUs handle many more threads in parallel.
The table below shows just how many threads each generation of NVIDIA GPU can have in flight at the same time:
| Fermi | GT200 | G80 | |
| Max Threads in Flight | 24576 | 30720 | 12288 |
Fermi can't actually support as many threads in parallel as GT200. NVIDIA found that the majority of compute cases were bound by shared memory size, not thread count in GT200. Thus thread count went down, and shared memory size went up in Fermi.
NVIDIA groups 32 threads into a unit called a warp (taken from the looming term warp, referring to a group of parallel threads). In GT200 and G80, half of a warp was issued to an SM every clock cycle. In other words, it takes two clocks to issue a full 32 threads to a single SM.
In previous architectures, the SM dispatch logic was closely coupled to the execution hardware. If you sent threads to the SFU, the entire SM couldn't issue new instructions until those instructions were done executing. If the only execution units in use were in your SFUs, the vast majority of your SM in GT200/G80 went unused. That's terrible for efficiency.
Fermi fixes this. There are two independent dispatch units at the front end of each SM in Fermi. These units are completely decoupled from the rest of the SM. Each dispatch unit can select and issue half of a warp every clock cycle. The threads can be from different warps in order to optimize the chance of finding independent operations.
There's a full crossbar between the dispatch units and the execution hardware in the SM. Each unit can dispatch threads to any group of units within the SM (with some limitations).
The inflexibility of NVIDIA's threading architecture is that every thread in the warp must be executing the same instruction at the same time. If they are, then you get full utilization of your resources. If they aren't, then some units go idle.
A single SM can execute:
| Fermi | FP32 | FP64 | INT | SFU | LD/ST |
| Ops per clock | 32 | 16 | 32 | 4 | 16 |
If you're executing FP64 instructions the entire SM can only run at 16 ops per clock. You can't dual issue FP64 and SFU operations.
The good news is that the SFU doesn't tie up the entire SM anymore. One dispatch unit can send 16 threads to the array of cores, while another can send 16 threads to the SFU. After two clocks, the dispatchers are free to send another pair of half-warps out again. As I mentioned before, in GT200/G80 the entire SM was tied up for a full 8 cycles after an SFU issue.
The flexibility is nice, or rather, the inflexibility of GT200/G80 was horrible for efficiency and Fermi fixes that.
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SiliconDoc - Friday, October 2, 2009 - link
Gee, you certaibnly are not a computer technician.That you even POSIT that games aren't played on INTEL GPU's is an astounding whack.
Nvidia and ati have laptop graphics, as does intel, and although I don't have the numbers for you on slot cards vs integrated, your whole idea is another absolute FUD and hogwash.
INTEL slotted graphics are still around playing games, bubbba.
You sure don't know much, and your point is 100% invalid, and contains the problem of YOUR TINY MIND.
Let me remind you Tamalero, you shrieked and wailed against nvidia for INTEGRATED GRAPHICS of theirs on a laptop !
Wow, you're a BOZO, again.
sandwiches - Friday, October 2, 2009 - link
You're a sad, pathetic troll, Silicondoc. I honestly do feel contempt for you. Your life is obviously devoid of any real substance.shotage - Thursday, October 1, 2009 - link
The performance and awesomeness of a company campared to another is biaised. Sure Nvidia probably has historically done better than ATI.I hope that ATI as a company does much better this year and next, so that the there is greater competition. Competition which will consequently mean smaller profit margins, but better deals for us consumers!
At the end of the day, who cares who's winning? Shouldn't we all be hoping that each does well? Shouldn't we all hope that there will always be several major graphics providers? Do we really want a monopoly on GPU's? How would this effect the price on a performance card?
I think you should be banned SiliconDoc. You're adding no real value here. Leave.
I have a GTX260 btw. So i'm not speaking from bias. Wander what kind of card you have? lol...
SiliconDoc - Friday, October 2, 2009 - link
What card you have or don't have doesn't matter one whit, but what you claim DOES. What you SPEW does !and when you lie expect any card to save you.
If liars were banned, you'd all be gone, and I'd be left. ( that does not include of course those who aren't trolling jerkbots running around to my every post wailing and whining and saying ABSOLUTELY NOTHING )
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" Sure Nvidia probably has historically done better than ATI."
since you 1. obviously haven't got a clue wether what you said is true or not 2. Why would you even say it, with your stupidty retaining, lack of knowledge, or lying caveat "probably" ?
If you're so ignorant, please shut it on the matter! Do you prefer to open your big fat yap and prove how knowledgeless you are ? I guess you do.
If you don't know, why are you even opening your piehole about it ?
It certainly doesn't do anything for me if you aren't correct and you don't know it ! I don't WANT YOUR LIES, nor your pie open when you haven't a clue. I don't want your wishy washy CRAP.
Ok ?
Got it ?
If you open the flapper, make sure it gets it right.
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If you actually are an enthusiast, why is it that the result is, you blather on in bland generalities, get large facts tossed in a fudging, sloppy, half baked inconclusive manner, and in the end, wind up being nothing less than the very red rooster you demand I believe you are not.
What a crappy outcome, really.---
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Frankly, you cannot accept me even telling the facts as they actually are, that is too much for your mushy, weak, flakey head, and when I do, you attribute some far out motive to it !
There's no motive other than GET IT RIGHT, YOU IDIOTS !
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What do you claim, though ?
Why is it, you have such an aversion to FACTS ? WHY IS THAT ?
If I point out ati is not in fact on top, but last, and NVIDIA is almost double ati, (to use the "authors" comparison techniques but not separate companies for "internal comparisons" and make CERTAIN I exagerrate) - why are you so GD bent out of shape ?
I'll tell you why...
YOU FORBID IT.
I certainly don't understand your mindset, you'd much prefer some puss filled bag of slop you can quack out so "we can come to some generalization on our desires and feelings" about "the industry".
Go suck down your estrogen pills with your girlfriends.
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I don't care what your feelings are, what flakey desire you have for continuing competition, because, you prefer LIES over the truth.
Instead of course, after you whining in some sissy crybaby pathetic wail for the PC cleche of continuing competition, you'll turn around and screech the competition I provide to your censored mindset is the worst kind you could possibly imagine to encounter ! Then you wail aloud "destroy it! get rid of it ! ban it ! "
LOL
You're one piece of filthy work, that's for sure.
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So, you want me to squeal like an idiot like you did, that you want lower prices and competition, and the way to get that is to LIE about ati in the good, and DISS nvidia to the bad with even bigger lies ?
I see.. I see exactly !
So when I point out the big fat lying fibs for ati and against nvidia - you percieve it as a great threat to "your bottom line" pocketbook.
LOL
Well you know what - TOO BAD ! If the card cannot survive on FACTS AND THE TRUTH, then it deserves to die.
Or is honesty banned so you can fan up ati numbers with your lies, and therefore get your cheaper nvidia card ?
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This is WHAT YOU PEOPLE WANT - enough lies for ati and against nvidia to keep the piece of red crappin ?
LOL yeah man, just like you jerks...
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" At the end of the day, who cares who's winning? "
Take a look at that you flaked out JERKOFF, and apply it to this site for the YEARS you didn't have your INSANE GOURD focused on me.
Come on you piece of filth, take a look in the mirror !
It's ALL ABOUT WHOSE WINNING HERE.
THE WHOLE SITE IS BASED UPON YOU LITTLE PIECE OF CRAP !
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And of course worse than that, after claiming you don't care whose winning, you go on to spread your hope that ati market share climbs, so you can suck down a cheapo card with continuing competition.
So what that says, is all YOU care about is your money. MONEY, your money.
"Quick ban the truth! jerkoffs pocketbook is threatened by posts on anandtech because this poster won't claim he wants equal market share !"
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Dude, you are disgusting. You take fear and personal greed to a whole new level.
sandwiches - Friday, October 2, 2009 - link
For some laughs at this poor excuse for a 29-year-old man, check out these links:Here, he was banned from driverheaven.com for his rants against ATI. He really is a truly rabid ATI hater with horribly sycophantic traits:
http://www.driverheaven.net/members/silicondoc.htm...">http://www.driverheaven.net/members/silicondoc.htm...
More rants by him about ATI and how great NVIDIA is:
http://www.maximumpc.com/user/silicondoc">http://www.maximumpc.com/user/silicondoc
http://forums.bit-tech.net/search.php?searchid=853...">http://forums.bit-tech.net/search.php?searchid=853...
Here's some political rant by Silicondoc. Is anyone surprised to learn he's also a rabid wingnut?
http://www.danielpipes.org/comments/118289">http://www.danielpipes.org/comments/118289
SiliconDoc - Friday, October 2, 2009 - link
Why that's great, let's see what you have for any rebuttal to this clone you claim is me:" Even the gtx260 uses less power than the 4870.
Pretty simple math - 295 WINS.
Cuda, PhysX, large cool die size, better power management, game profiles out of the box, forced SLI, better overclocking, 65% of GPU-Z scores and marketshare, TWIMTBP, no CCC bloat, secondary PhysX card capable, SLI monitor control "
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Anything there you can refute ? Even just one thing ?
I'm not sure what your complaint is if you can't.
That's the text that was there, so why didn't you read it or try to claim anything in it was wrong ?
Are you just a little sourpussed spasm boy red, or do you actually have a reason ANY of that text is incorrect ?
Anything at all there ? Are you an empty shell who copies the truth then whines like a punk idiot ? Come on, prove you're not that pathetic.
wifiwolf - Thursday, October 1, 2009 - link
less margins indeed. At a business point of view though that's good anyway, not because less margins is good for business (of course not) but for what it implies. It means factories can keep on maximum production - and that's very important. There's less profit for each sale but number of consumers is bigger in an exponential way. So not bad indeed... even for them - good for all.Zingam - Thursday, October 1, 2009 - link
Fermi he hassilverblue - Thursday, October 1, 2009 - link
Doesn't matter mate, he'll still just accuse you of bias and brown-nosing ATI.Jamahl - Thursday, October 1, 2009 - link
Silicondoc, go see a REAL doc please.