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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rennya - Thursday, October 1, 2009 - link
I have already countered your suggestion that ATI 5870 is just a paper launch, somewhere in this same discussion.Plus, if nVidia really has working silicon as you showed in the fudzilla link, where then I can buy it? Even at the IDF, Intel shows working silicon for Larrabee (although older version), but not even the die-hard Intel fanboys will claim that Larrabee will be available soon.
SiliconDoc - Thursday, October 1, 2009 - link
Gee, we have several phrases. Hard launch, and paper launch. Would you prefer something in between like soft launch ?Last time nvidia had a paper launch, that what everyone called it and noone had a problem, even if cards trickled out.
So now, we need changed definitions and new wordings, for the raging little lying red roosters.
I won't be agreeing with you, nor have you done anything but lie, and attack, and act like a 3 year old.
It's paper launch, cards were not in the channels on the day they claimed they were available. 99 out of 100 people were left bone dry, hanging.
Early today the 5850 was listed, but not avaialable.
Now, since you people and this very site taught me your standards and the definition and how to use it, we're sticking to it when it's a god for saken red rooster card, wether you like it or not.
rennya - Friday, October 2, 2009 - link
You defined hard launch as having cards on retail shelf.That's what happened here in the first couple of days at the place I lived in. So, according to your standard, 5870 is a hard launch, not paper launch or soft launch. I can easily get one if I want to (but my casing is just crappy TECOM mid-tower, the card will not fit).
As far as I am concerned, 5870 has a successful hard launch. You tried to tell people otherwise, that's why I called you a liar.
Where to know where I live? Open up the Lynnfield review at http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?... then look at the first picture in the first page. It shows you the country where I am posting this post from. The same info can also be seen in AMD Athlon X4 620 review at http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?... . The markup from MRSP can be ridiculous sometimes, but availability is not a problem.
Zingam - Thursday, October 1, 2009 - link
This CPU is for what? Oh, Tesla - the things that cost 2000 :) And the consumers won't really get anything more by what ATI offers currently!Seems like it is time for ATI to do a paper launch.
Just to inform the fanboys: ATI has already finalized the specs for generation 900 and 1000. The current is just 800.
So on paper, dudes, ATI has even more than what they are displaying now!
BTW who said: DX11 won't matter?? :)
cactusdog - Thursday, October 1, 2009 - link
Its unbelievable that Nvidia wont have a DX11 chip in 2009. Massive fail.strikeback03 - Thursday, October 1, 2009 - link
Not if there are no worthwhile DX11 games in 2009.yacoub - Wednesday, September 30, 2009 - link
"Perhaps Fermi will be different and it'll scale down to $199 and $299 price points with little effort? It seems doubtful, but we'll find out next year."Yeah okay, side with their marketing folks. God forbid they actually release reasonably-priced versions of Fermi that people will actually care to buy.
SiliconDoc - Thursday, October 1, 2009 - link
Derek did an article not long ago on the costs of a modern videocard, and broke it down part and piece by cost, each.Was well done and appeared accurate, and the "margin" for the big two was quite small. Tiny really.
So people have to realize fancy new tech costs money, and they aren't getting raked over the coals. its just plain expensive to have a shot to the moon, or to have the latest greatest gpu's.
Back in '96 when I sold a brand new computer I doubled my investment, and those days are long gone, unles you sell to schools or the government, then the upside can be even higher.
yacoub - Thursday, October 1, 2009 - link
And yet all of that is irrelevant if the product cannot be delivered at a price point where most of the potential customers will buy it. You're forgetting that R&D costs are not just "whatever they will be" but are based off what the market will support via purchasing the end result. It all starts withe the consumer. You can argue all you want that Joe Gamer should buy a $400 GPU but he's only capable of buying a $300 GPU and only willing to buy a $250 GPU, then you're not going to get a sale until you cross the $300 threshold with amazing marketing and performance or the $250 threshold with solid marketing and performance. Companies go bust because they overspend on R&D and never recoup the cost because they can't price the product properly for it to sell the quantities needed to pay back the initial investment, let alone turn a significant profit.Arguing that gamers should just magically spend more is silly and shows a lack of understanding of economics.
SiliconDoc - Thursday, October 1, 2009 - link
Well I didn't argue that gamers should magically spend more.--
I ARGUED THAT THE VIDEOCARDS ARE NOT SCALPING THE BUYERS.
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Deerek's article, if you had checked, outlined a card barely over $100.00
But, you instead of thinking, or even comprehending, made a giant leap of false assuming. So let me comment on your statements, and we'll see where we agree.
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1. Ok, the irreverance(yes that word) here is that TESLA commands a high price, and certainly has been stated to be the profit margin center (GT200) for NVIDIA- so...whatever...
- Your basic points are purely obvious common sense, one doesn't even need state them - BUT - since Nvidia has a profit driver where ATI does not, if you're a joe rouge, admitting that shouldn't be the crushing blow it apparently is.
2. Since Nvidia has been making the MONEY, the PROFIT, and reinvesting, I think they have a handle on what to spend, not you, and their sales are much higher up to recoup costs, not sales, to you, your type.
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Stating the very simpleton points of even having a lemonade stand work out doesn't impress me, nor should you have wasted your time doing it.
Now, let's recap my point: " So people have to realize fancy new tech costs money, and they aren't getting raked over the coals."
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That's a direct quote.
I also will reobject your own stupidty : " You're forgetting that R&D costs are not just "whatever they will be" but are based off what the market will support via purchasing the end result."
PLEASE SEE TESLA PRICES.
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Another jerkoff that is SOOOOOOOO stupid, finds it possible that someone would even argue that gamers should just spend more money on a card, and - after pointing out that's ridiculous, feels he has made a good point, and claims, an understanding of economics.
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If you don't see the hilarity in that, I'm not sure you're alive.
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Where do we get these brilliant analysts who state the obvious a high schooler has had under their belt for quite some time ?
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I will say this much - YOU specifically (it seems), have encountered in the help forums, the arrogant know it all blowhards, who upon say, encountering a person with a P4 HT at 3.0GHZ, and a pci-e 1.0 x16 slot, scream in horror as the fella asks about placing a 4890 in it. The first thing out of their pieholes is UPGRADE THE CPU, the board, the ram, then get a card....
If that is the kind of thing you really meant to discuss, I'd have to say I'm likely much further down that bash road than you.
You might be the schmuck that shrieks "cpu limitation!, and recommends the full monty reaplcements"
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Let's hope you're not after that simpleton quack you had at me.