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Question AMD Rembrandt/Zen 3+ APU Speculation and Discussion

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Kepler_L2

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Sep 6, 2020
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Really? What makes you say that?
PS5 has Navi 2, not Navi 1, and this driver is very recent (committed some mounths ago).
Notebookcheck has the same intuition.
Maybe it won't be Cyan Skillfish, maybe RDNA2, but I still think a light version of it (few CUs).
If you check the Linux SMU patches, you will see it's an 8 Core Zen 2 APU. Also LLVM shows gfx1013 (Cyan skillfish) has RT support.
 

Doug S

Senior member
Feb 8, 2020
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If anyone could benefit from stacked cache it would seem to be Ampere. Maybe they don't care if the small SLC that hurts them in some benchmarks doesn't really impact their target cloud market. But stick a 7nm die the size of the 128 core chip that's entirely SRAM and that SLC goes from 16MB to 1GB for only a modest increase in latency.
 

uzzi38

Golden Member
Oct 16, 2019
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If anyone could benefit from stacked cache it would seem to be Ampere. Maybe they don't care if the small SLC that hurts them in some benchmarks doesn't really impact their target cloud market. But stick a 7nm die the size of the 128 core chip that's entirely SRAM and that SLC goes from 16MB to 1GB for only a modest increase in latency.
They don't care at all. Their focus is not per-core performance - you'll never see them do that frankly.
 

LightningZ71

Senior member
Mar 10, 2017
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Let's not forget: The desktop 3400g had 11 CUs and could routinely clock north of 1600mhz. 12 CUs of RDNA 2, while being more efficient and likely clocked above 2Ghz in some parts, isn't a massive uplift. Assuming that the DDR5 can keep it fed, I'd still be shocked if it consistently reached RX560/1050 levels of in game performance.
 
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TESKATLIPOKA

Senior member
May 1, 2020
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Let's not forget: The desktop 3400g had 11 CUs and could routinely clock north of 1600mhz. 12 CUs of RDNA 2, while being more efficient and likely clocked above 2Ghz in some parts, isn't a massive uplift. Assuming that the DDR5 can keep it fed, I'd still be shocked if it consistently reached RX560/1050 levels of in game performance.
RDNA2 vs Polaris(Vega) is 33-40% better per clock at the same number of CU compared to Polaris(Vega).
A desktop 12CU RDNA2 can clock easily to at least 2.5GHz.
This all adds to more than 2x better performance. If this is not a massive uplift then I don't know what is.
Of course bandwidth could be a problem, but If they couldn't feed It properly, then they wouldn't put 12CU inside Rembrandt.

Can It beat RX560/1050 levels of game performance?
3400g = 11CU(704SP) at 1600Mhz -> 2250 GFLOPs
RX560 = 16CU(1024:64:16) at 1175(1275) MHz -> 2406(2611) GFLOPs
GTX 1050 = 5SM (640:40:32 ) at 1354 (1455 ) MHz -> 1733 (1862) GFLOPs
Rembrandt = 12CU(768SP) at 2.5GHz -> 3840 GFLOPs
If It can't beat It, I would be surprised.
 
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LightningZ71

Senior member
Mar 10, 2017
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Your own chart works against your point. The RX 560, despite having a near 50% GFlop advantage over the 1050, is almost always beaten by the 1050 in game benchmarks, and its only wins are by very slim margins. The 3400G, despite having 90% of the GFlops of the RX 560, is almost never even close to meeting the 560 in game benchmarks. Bandwidth starvation is a big deal.

RDNA2 is definitely more efficient in using VRAM, but, is it good enough to overcome the limits imposed by dual-dual channel DDR5, the actual bandwidth of which won't be more than 50% greater than the 3200 DDR4, and the few LPDDR4X 4333 implementations that we've already seen? I hope it's something special, but I'm not holding my breath, especially since they chose not to include any infinity cache for it, which seems to be a large part of why RDNA2 does so well with limited bandwidth in other GPUs.
 

uzzi38

Golden Member
Oct 16, 2019
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It might not, idk. Early rumours make it sound rather meh, we'll have to see, it could be memory bandwidth is a much bigger issue than first expected.
 

TESKATLIPOKA

Senior member
May 1, 2020
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Your own chart works against your point. The RX 560, despite having a near 50% GFlop advantage over the 1050, is almost always beaten by the 1050 in game benchmarks, and its only wins are by very slim margins. The 3400G, despite having 90% of the GFlops of the RX 560, is almost never even close to meeting the 560 in game benchmarks. Bandwidth starvation is a big deal.
It doesn't work against my point, It just shows GFLOPs, but doesn't take into account the GPU architecture or bandwidth. For example as I already mentioned RDNA2 is 33-40% faster than Polaris at the same GFLOPs.
Pascal is also faster than Polaris at the same GFLOPs, not to mention Pascal clocks higher than what It's official boost suggests, just take a look at some old Pascal GPU reviews.
You mention 3400g having 90% GFLOPs of RX560, but that's not true. I used 1.6GHz, because you said It can clock that high, but officially It has only 1.4GHz or 1971GFLOPs and that's only 76% of RX 560 boost.

If I compare Rembrandt IGP vs the new RX 6600, then Rembrandt IGP would need 6000Mhz DDR5 to have the same GFLOPs/BW ratio, but that's at ~2.45GHz.
4800Mhz DDR5 is good enough for 1960Mhz IGP clockspeed. The problem is RX6600 has Infinity cache, but Rembrandt won't have any.
 
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May 1, 2020
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It might not, idk. Early rumours make it sound rather meh, we'll have to see, it could be memory bandwidth is a much bigger issue than first expected.
As I understood RDNA2 is more efficient wrt bandwidth than Vega. I heard about around 30% but have no source to link to.
 

eek2121

Golden Member
Aug 2, 2005
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FYI, I've been hearing that the upcoming Rembrandt release is OEM only and consumer parts (including AM5) will NOT be released.

EDIT: That is, consumer AM5 boards will be introduced with Zen 4.
 
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ahimsa42

Member
Jul 16, 2016
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FYI, I've been hearing that the upcoming Rembrandt release is OEM only and consumer parts (including AM5) will NOT be released.

EDIT: That is, consumer AM5 boards will be introduced with Zen 4.
makes sense since Rembrandt is a mobile CPU so will be for laptops, all in one desktops & mini PC's.
 

Rannar

Member
Aug 12, 2015
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the performance of the steam deck bodes well so hoping to see rembrandt U at worst = to rx 560, at best = to rx 570
at best not coing to happen. rx 570 is 5+ TFLOPS with 224-256GB/s of bandwith. 45W H will land probably between gtx1050- gtx1650 . 15W below gtx1050
 

TESKATLIPOKA

Senior member
May 1, 2020
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the performance of the steam deck bodes well so hoping to see rembrandt U at worst = to rx 560, at best = to rx 570
Rembrandt U will certainly not perform as RX 570.
Even a desktop part wouldn't perform as high.
Rannar could be pretty close with his estimate.
IGP performance crown will be once again held by AMD.
 

ahimsa42

Member
Jul 16, 2016
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at best not coing to happen. rx 570 is 5+ TFLOPS with 224-256GB/s of bandwith. 45W H will land probably between gtx1050- gtx1650 . 15W below gtx1050
from what i have read there is not much difference if any between a 5800U & a 5800H when it comes to gaming
 

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