Question Speculation: RDNA2 + CDNA Architectures thread

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uzzi38

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Oct 16, 2019
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All die sizes are within 5mm^2. The poster here has been right on some things in the past afaik, and to his credit was the first to saying 505mm^2 for Navi21, which other people have backed up. Even still though, take the following with a pich of salt.

Navi21 - 505mm^2

Navi22 - 340mm^2

Navi23 - 240mm^2

Source is the following post: https://www.ptt.cc/bbs/PC_Shopping/M.1588075782.A.C1E.html
 

TESKATLIPOKA

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May 1, 2020
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I love how things are in discussion twisted.

I was talking about 40 CU GPU being 10% above RTX 2080 Super or 35% above RX 5700 XT.

I've just checked the performance comparison with RTX 2080 Super in TPU suite. Well, if we look at TechPowerUp charts, RTX 2080 Super in 4K is 25% above RX 5700 XT.
relative-performance_3840-2160.png


Secondly. Thats the performance level that RTX 3070 will achieve, even according to Galax:

So lets get back to the discussion. How come 40 CU GPU chip cannot compete with RTX 3070, while clocked at 2.3 GHz and having 10% higher IPC than RDNA1 GPUs?

Can anyone explain this to me? From the start, Im trying to tell people that RTX 3070 WILL NOT ACHIEVE RTX 2080 Ti performance levels. I don't know why people believe in this, and spin the discussion that in order to compete with RTX 3070, 40 CU GPU has to beat RTX 2080 Ti.

Its absolutely ridiculous how overestimated Nvidia is, and their Ampere GPUs.
RTX 2080 vs RTX 2080 Ti -> Ti is 26% faster
RTX 2080 vs RTX 3070 -> pretty much the same specs(SMs, TMUs, ROPs, Bandwidth) except the number of FP32 cores.
RTX 3070 is then only 14.4% faster than 2080, 8% faster than Super and 2080Ti is only 10% faster. Ok, this is possible, but Bandwidth is a bottleneck in my opinion, 16Ghz would bring extra performance.
Back to Navi2x with 40CU.
RX 5700XT has 1887Mhz clockspeed on average.
2.3GHz is actually 21.9% higher and with 10% IPC It's actually 100*1.1*1.219=134%, let's say 35% faster as a combination of clocks and IPC. This is not impossible, but the bigger problem for me is only 150W TBP and bandwidth If It's only 192bit. 192bit bus with 14-16GHz GDDR6 provides 336-384GB/s which is 14-25% less compared to 448GB/s of RX5700 XT while feeding a 35% faster chip. I would expect 256bit bus with 14-16GHz memory. TBP I won't comment, I did It more than once in the past.
 
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TESKATLIPOKA

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May 1, 2020
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Simplest possible calculations.

RTX 3080 is 25-30% faster than RTX 2080 Ti.

RTX 3080 has 68 SMs, massive bandwidth.

So how come suddenly 44 CU GPU, will achieve RTX 2080 Ti performance, considering that RTX 3080 has 54%(!) more SMs? And does not use GDDR6X, but only GDDR6?

How will it mitigate the undeniable lack of hardware? Nvidia's magic?

So maybe that 40CU has way smaller hill to climb, despite what people want to believe?
RTX 3070 does not have 44CU but 46SM.;)
 
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Timorous

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Oct 27, 2008
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RTX 2080 vs RTX 2080 Ti -> Ti is 26% faster
RTX 2080 vs RTX 3070 -> pretty much the same specs(SMs, TMUs, ROPs, Bandwidth) except the number of FP32 cores.
RTX 3070 is then only 14.4% faster than 2080, 8% faster than Super and 2080Ti is only 10% faster. Ok, this is possible, but Bandwidth is a bottleneck in my opinion, 16Ghz would bring extra performance.
Back to Navi2x with 40CU.
RX 5700XT has 1887Mhz clockspeed on average.
2.3GHz is actually 21.9% higher and with 10% IPC It's actually 100*1.1*1.219=134%, let's say 35% faster as a combination of clocks and IPC. This is not impossible, but the bigger problem for me is only 150W TBP and bandwidth If It's only 192bit. 192bit bus with 14-16GHz GDDR6 provides 336-384GB/s which is 14-25% less compared to 448GB/s of RX5700 XT while feeding a 35% faster chip. I would expect 256bit bus with 14-16GHz memory. TBP I won't comment, I did It more than once in the past.

I think 3070 vs 2080Ti will be like 5700XT vs R7. At 1080p and 1440p they might be very close but at 4k the 3070 will fall behind slightly in the comparison like 5700XT does.

PS5 is 2.23Ghz peak on the GPU. I can see a 40 CU RDNA2 gpu matching the 2080S. 12 Tflops of Series X is already getting a baseline of 2080 level performance in a really quick port.

The 5700XT has 225W tbp. When AMD compared navi to GCN they compared products not just the dies so on the basis they are doing that again it suggests they can hit 2080Ti performance at 225w tbp. It also suggests they could hit 5700XT perf with a 150W tbp. Given this it would mean that to hit 5700XT +32% the 40CU part would need to have a 200W tbp.

Looking at PS5 vs Series X power supplies it seems that it could go either way because the difference could be down the the PS5 SSD IO arrangement being more power hungry or the audio engine rather than SoC power. These power supplies are also undersized if the GPU in the SoC + Ram is consuming 200W on their own meaning if the performance is there AMD could have beaten their stated 50% perf/watt goal (I bet they had a higher internal target).
 

Antey

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Jul 4, 2019
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just imagine a big vega (power consumption would be beyond insane though)... 80 Compute Units, 5120 stream processors, 2,3GHz... 5120*2*2,3= 23,55 TFLOPs. if radeon 7 is 13,44 TFLOPs then it would be 75% faster... that would be 26% faster than the 2080ti (based on that techpowerup relative perf data)... hey! not bad.
 
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TESKATLIPOKA

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May 1, 2020
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just imagine a big vega (power consumption would be beyond insane though)... 80 Compute Units, 5120 stream processors, 2,3GHz... 5120*2*2,3= 23,55 TFLOPs. if radeon 7 is 13,44 TFLOPs then it would be 75% faster... that would be 26% faster than the 2080ti (based on that techpowerup relative perf data)... hey! not bad.
Wrong. Vega TFLOPs don''t provide the same performance as RDNA1 or RDNA2 TFlops. Just compare Radeon VII vs RX 5700 XT.
 
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TESKATLIPOKA

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What? I'm not talking about RDNA or RDNA2... Radeon 7 is GCN5 Vega.
I see, my bad, didn't notice you mentioning big Vega at the beginning, but even so It wouldn't be 75% faster. BTW I don't see a reason for bringing up a hypothetical Big Vega when we have RDNA2 Big Navi.
 
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Antey

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Yes, RDNA has much better use of its resources and can provide a better gaming performance. you are saying that vega tflops and gaming performance doesnt scale linearly? (with pixel fillrate and bandwidth increased accordingly)
 

TESKATLIPOKA

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First of all, the question is If you also doubled the ROPs and significantly increased the bandwidth or just doubled the CU number in your calculation. Even If you doubled everything, then the scaling is never linear or at least I didn't see It with any GPU.

Edit: actually it is almost linear in 4K at least with RDNA1, If there is enough ROPs and bandwidth.
You can compare RX5500XT 8GB vs RX5700XT 8GB(+87% in TFLOPs and ROPs, bandwidth is doubled)
difference:
FullHD: +79%
WQHD: +83%
4K: +86%
Review
 
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Antey

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mmmh ok, i will try it.

5500XT has 22CU / 1408 SM at 1,845 MHz (boost max) or 1717 MHz for gaming freq; thats 5195 / 4835 GFLOPS
5700XT has 40CU / 2560 SM at 1905 MHz (boost max) or 1755 MHz for gaming freq; thats 9753 / 8986 GFLOPS

5500XT boost 100% -> 5700XT boost 188%
5500XT gaming 100% -> 5700XT gaming 186%


i'm going to use 4k data because is close to not CPU bottlenecked (isn't it?)

5500XT 4K gaming perf 100% -> 5700XT 4K gaming perf 186%

i dont know friend, that very linear to me.
 

TESKATLIPOKA

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True, I checked It once more using the measured average clockspeed from the review and It's almost linear in 4K.

edit:
I checked also Polaris RX 460 vs RX 470 and there we can see a difference. Vega doesn't have a halved version.
ASUS Radeon RX 460 STRIX OC 4GB Review vs ASUS Radeon RX 470 STRIX OC 4 GB Review
Specs:
TFLOPs: 2.262Tflops vs 4.706Tflops (+108%)
Clockspeed: 1262Mhz vs 1149Mhz (-9%)
CU: 14 vs 32 (+129%)
ROP: 16 vs 32 (+100%)
Bandwidth: 112GB/s vs 211GB/s (+88%)

Performance difference:
FullHD: +79%
WQHD: +82%
4k: +76%
 
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leoneazzurro

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Jul 26, 2016
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Of course, another issue with prediction is that there will be for sure changes in the architecture that may affect performance in a positive or negative way. I.e. the rumors about a narrow bus may point to a negative factor, utlization in a CU should increase, and there was a rumor about a complete overhaul of RBEs
 

leoneazzurro

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Well not only that, there was Katcorgi or Rogame (sorry, I don't remember who) saying Big Navi had 128 ROPs with fewer RBE partitions... Pointing to something fishy going on on that side
 

Hitman928

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CastleBravo

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Now that the 3090 reviews are out, it looks like straight doubling of 5700xt performance will put AMD in a competitive position with NV's entire stack for 1080 and 1440p at least, and within striking distance of the 3090 at 4k (although falling a bit short).

If Navi21 has right at 2x Navi10's 4k performance, it will be less than 2x on 1440 and 1080.