AMD: Navi Speculation, Rumours and Discussion [2019]

Discussion in 'Architecture and Products' started by Kaotik, Jan 2, 2019.

  1. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    TSMC says 7nm compared to 16nm (12nm should be pretty same) 65% less power at same performance or 35 - 40 % more performance at same power, that's lightyears away from +50% performance at -50% power, too far for mere architectural improvements save for some holy grail -like revolutionary new discovery that would transform the whole field.
    Only way I can see that holding any light would be some specific scenario like pure RT-performance
     
    w0lfram and BRiT like this.
  2. trinibwoy

    trinibwoy Meh
    Legend

    Joined:
    Mar 17, 2004
    Messages:
    10,782
    Likes Received:
    914
    Location:
    New York
    That performance refers to transistor switching speed correct? Which translates to clock speed. I don’t know how useful those numbers are. We know GPU performance increases primarily due to having more transistors, not faster ones. So I read that as 55% (1/0.65) more transistors at the same power. Then add any architecture efficiency gains on top of that.

    Though 50% faster at 50% lower power is far fetched by any measure.
     
  3. Benetanegia

    Regular Newcomer

    Joined:
    Sep 4, 2015
    Messages:
    344
    Likes Received:
    316
    You are forgetting about over 3x density and subsequent 3x amount of transistors. The numbers 65% less power or 35% more performance numbers refer to perf/power of transistors, not the chip. A really straightforward, with no architectural improvements involved at all, way of obtaining what the rumors claimed would be to put 3x as many transistors at the same transistor performance. So 3x transistors @ 35% power.
     
  4. Miniature Kaiju

    Newcomer

    Joined:
    Jun 10, 2019
    Messages:
    51
    Likes Received:
    58
    Nope, it's perf/power of the chip. What it means it's that the same chip, just shrunk down to the new node, can get you either a 65% reduction in power OR a 35% increase in perf through clocks. Yes, there's still the density increase to be explored, but power draw increases roughly linearly with transistor count, they don't come for free.
     
    w0lfram likes this.
  5. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    As @Miniature Kaiju pointed out, the numbers are for theoretical chip which gets shrunk, not one with 3x the transistors. "65% less power" means the same chip running at same clocks should consume 65% less and "35% more performance" that running the same chip at 35 % higher clocks should use same amount of power (as previous process at those lower clocks)

    As for the density, theory and real life chips aren't exactly the same.
    Coming from Vega 10 on GloFo 14nm to Navi 10 on TSMC 7nm, theoretically density could have improved slightly over 100% (so 2x density), but in reality it only improved little over 60%.
    The "3x density" TSMC talks about is for the low power "mobile" variant of 7nm process (96.5 Mtrans/mm2), high performance "HPC" variant gets only 66.7 Mtrans/mm2 which isn't even double the 12nm density (33.8 Mtrans/mm2).
    Since NVIDIA is coming from TSMC 12nm, they should actually yield slightly lower density improvements compared to AMD coming 14nm (they used same libraries on 12nm so they didn't take advantage of 12nm's possible density benefits). GloFo 14nm theoretically has 32.5Mtrans/mm2 density
     
  6. trinibwoy

    trinibwoy Meh
    Legend

    Joined:
    Mar 17, 2004
    Messages:
    10,782
    Likes Received:
    914
    Location:
    New York
    I just realized it’s 65% “less” power so I have to adjust my math a bit. Assuming perfect scaling that means a chip with 2.85x the transistors will consume the same power.

    Now obviously reality will be nowhere near that but even 2x would be huge. Question is how come Navi got the density improvement but not the expected reduction in power consumption?
     
  7. DegustatoR

    Veteran

    Joined:
    Mar 12, 2002
    Messages:
    1,683
    Likes Received:
    503
    Location:
    msk.ru/spb.ru
    Had to be clocked out of its optimal frequency window to compete with Turing?
     
    w0lfram and A1xLLcqAgt0qc2RyMz0y like this.
  8. Benetanegia

    Regular Newcomer

    Joined:
    Sep 4, 2015
    Messages:
    344
    Likes Received:
    316
    That's the same I said. The catch is the bolded part "performance through clocks", which is why:

    Exactly, so when in the same die size, you can have 3X amount of transistors (properly used that would mean 3x execution units), each drawing roughly 1/3 the power as before, what do you get? Exactly 3X performance at equal power consumption. And if you make a chip that is half the size? 1.5x performance at 0.5x power, or in other words 50% higher performance at 50% lower power.
     
  9. Miniature Kaiju

    Newcomer

    Joined:
    Jun 10, 2019
    Messages:
    51
    Likes Received:
    58
    You won't get anywhere near a 3x increase in density for anything performant, though. You'll get barely a 2x increase going from 12nm to 7nm.

    Also, it's worth noting that transistor count doesn't translate linearly to perf.
     
  10. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    Probably even less, AMD got only 65% coming from less dense GloFo 14nm compared to TSMC 12nm
     
  11. Benetanegia

    Regular Newcomer

    Joined:
    Sep 4, 2015
    Messages:
    344
    Likes Received:
    316
    That remains to be seen. All previous generations have achieved something really close ti theoretical, for example Pascal saw a 1.7x density increase on 1.9x density node. 16/12nm to 7nm TSMC is a 3.3x, so 3x is not out of the question. Plus Pascal relied heavily on increasing clocks, while here we'd be talking about lowest power at no increased clocks, which is always going be accompanied with relatively higher densities if both cases are pushed to the max.

    Of course it does all things being equal. It can even bring larger than linear performance increases if one can concentrate those transistors on performance producing units.
     
  12. Benetanegia

    Regular Newcomer

    Joined:
    Sep 4, 2015
    Messages:
    344
    Likes Received:
    316
    You can't use a completely different company, coming from a completely different foundry, with a completely different architecture and where there's a million unknowns about what changes were needed to make a conclusion on how well 7nm scales.

    EDIT: Oh and I'm pretty sure GloFo 14nm has always been considered denser than TSMC's.
     
  13. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    GloFo 14nm (32.5 MTrans/mm^2) is denser than TSMC 16nm (28.2 MTrans/mm^2) but less dense than TSMC 12nm (33.8 MTrans/mm^2).

    Reported transistor densities should be comparable between fabs and given design should require roughly same amount of transistors no matter the manufacturer. Sure there might are some differences, but when we're talking about numbers rounded to 100s of thousands, it should be within the margin of error. (Also TSMC and their processes are by no means unknown to AMD, they've designed chips for their 16nm too)

    Also, for what it's worth, with Vega 20 they only managed to squeeze density up by 58 % compared to Vega 10.
     
  14. w0lfram

    Newcomer

    Joined:
    Aug 7, 2017
    Messages:
    240
    Likes Received:
    40
    So Turing, going to Ampere is going to gain 60% more die space, at same watts?
     
  15. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    Probably. Unless they go straight for N7+, that would of course change things, I'm just assuming it's N7 until someone confirms EUV
     
  16. DegustatoR

    Veteran

    Joined:
    Mar 12, 2002
    Messages:
    1,683
    Likes Received:
    503
    Location:
    msk.ru/spb.ru
    12FFC is not the same thing as 12FFN. Turing is 12FFN.
     
  17. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    So are you suggesting it's similar to AMD using old "14nm libraries" with GloFo 12nm? Then the increase in density should be slightly higher than the number I used of course. Regardless, at 12/14/16nm processes AMD and NVIDIA GPUs have had quite similar densities from 22 to 25 Mtrans/mm^2 or so
     
  18. Benetanegia

    Regular Newcomer

    Joined:
    Sep 4, 2015
    Messages:
    344
    Likes Received:
    316
    Yeah but it's not the same situation, even if the densitiy numbers are similar. I mean, Nvidia being 25 Mtrans/mm^2 on a 28.2 Mtrans/mm^2 node vs AMD being 25 Mtrans/mm^2 on a 32.5 MTrans/mm^2 is quite a different story. We are talking a 88% vs 75% of the node's maximum density achieved.

    But that's not even the problem, because it's Navi that is the big elephant in the room with 40 Mtrans/mm^2 in a node that should be able to provide at least 65 Mtrans/mm^2, let alone 90 Mtrans/mm^2 if low power cells are used. That's just 63% and taking it for comparison is obviously skewing the results.

    If Nvidia achieved 88% of 65 Mtrans/mm^2, we would be talking about a 2.3x increase in density, but still we don't know what kind of libraries were used in each case, so I stand by my previous claims.
     
  19. Kaotik

    Kaotik Drunk Member
    Legend

    Joined:
    Apr 16, 2003
    Messages:
    9,248
    Likes Received:
    3,193
    Location:
    Finland
    NVIDIA didn't reach any higher with Samsung 14nm which is the same process as GloFo 14nm, 24-25 MTrans/mm^2. Also it's not just Navi 10 & 14, Vega 20 also has 40-41 MTrans/mm^2 density
     
    w0lfram likes this.
  20. trinibwoy

    trinibwoy Meh
    Legend

    Joined:
    Mar 17, 2004
    Messages:
    10,782
    Likes Received:
    914
    Location:
    New York
    That certainly seems to be the case for the 5700xt but the 5600xt is showing much better perf/watt even at relatively high clocks.

    The voltage/frequency curve for Navi isn’t much better than Turing though so there’s definitely room for improvement.
     
Loading...

Share This Page

  • About Us

    Beyond3D has been around for over a decade and prides itself on being the best place on the web for in-depth, technically-driven discussion and analysis of 3D graphics hardware. If you love pixels and transistors, you've come to the right place!

    Beyond3D is proudly published by GPU Tools Ltd.
Loading...