Discussion Speculation: Zen 4 (EPYC 4 "Genoa", Ryzen 7000, etc.)

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Vattila

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Oct 22, 2004
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Except for the details about the improvements in the microarchitecture, we now know pretty well what to expect with Zen 3.

The leaked presentation by AMD Senior Manager Martin Hilgeman shows that EPYC 3 "Milan" will, as promised and expected, reuse the current platform (SP3), and the system architecture and packaging looks to be the same, with the same 9-die chiplet design and the same maximum core and thread-count (no SMT-4, contrary to rumour). The biggest change revealed so far is the enlargement of the compute complex from 4 cores to 8 cores, all sharing a larger L3 cache ("32+ MB", likely to double to 64 MB, I think).

Hilgeman's slides did also show that EPYC 4 "Genoa" is in the definition phase (or was at the time of the presentation in September, at least), and will come with a new platform (SP5), with new memory support (likely DDR5).

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What else do you think we will see with Zen 4? PCI-Express 5 support? Increased core-count? 4-way SMT? New packaging (interposer, 2.5D, 3D)? Integrated memory on package (HBM)?

Vote in the poll and share your thoughts! :)
 
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Thibsie

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Apr 25, 2017
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Some of that like core-on-core stacking almost seems like it would be infeasible due to issues with heat dissipation. I suppose it could work if you had a very clever layout and employed rotation of some sort so that the problem areas don't overlap or if the clock speeds were intentionally kept low enough where nothing gets too hot, but that does potentially preclude it from some products.

Stack big cores on top of more low power utilitarian cores ?
 

Joe NYC

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Jun 26, 2021
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Stack big cores on top of more low power utilitarian cores ?

I wonder if a more fruitful approach would rather be just a fast interconnect at an intersect of dies.

Suppose there are 2 rectangular dies, and instead of stacking them on top of each other, the dies instead form an "L".

This way, nearly all of the surface area is eligible for contact with heatsink.

Looking at a package such as Milan, the area of the MCM is perhaps > 3x the area of the sum of the areas of the dies. So there is a plenty of space Even in Ryzen desktop chips.

In your example, the low power and high power don't have to be on top of each other for better performance (unlike, say L3). They just benefit from a fast link. So the small dies could be the horizontal part of the "L" and big cores the vertical part of the "L" and both would have heatsink on top of most of their area.
 

DisEnchantment

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Mar 3, 2017
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All of the biggliest details from the Gigabyte leak for Zen 4:

GenZ and CXL in one go, awesome. SIs will be mighty pleased. NVDIMM-P seems supported as was in the original roadmap a long time ago.
The next gen servers from Intel and AMD would be transformative

Very sad that info has to come this instead of being willingly shared by AMD (like for example Intel Architecture day or previous Horizon events)
 

DisEnchantment

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Mar 3, 2017
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Seems the Zen4 APUs will support DP2.0, as per the block diagram for AM5 IO, which is not currently supported by RDNA2.
It could be a new update of DCN for RDNA2 iGPUs for which the support was planned to be added to Linux in this patch

 

Mopetar

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Jan 31, 2011
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There are solution being studied for cooling 3D stacked logic, i.e. by using a fluid inside the silicon stack.

That sounds interesting but difficult in reality since you need to use something that isn't going to expand too much at the sizes that are being used in top of a whole lot of other issues you'd run into at that level.

If you've got bottled anything it wants to expand as it heats up and that exerts more pressure on the container which needs to be strong enough to withstand that but also small enough to fit in a chip between the layers without ballooning the size too much or causing damage to the other layers.
 

leoneazzurro

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Jul 26, 2016
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That sounds interesting but difficult in reality since you need to use something that isn't going to expand too much at the sizes that are being used in top of a whole lot of other issues you'd run into at that level.

If you've got bottled anything it wants to expand as it heats up and that exerts more pressure on the container which needs to be strong enough to withstand that but also small enough to fit in a chip between the layers without ballooning the size too much or causing damage to the other layers.

Well this is why it is still at study and not already implemented (btw, if you keep the fluid flowing and without changing state there is no problem in the fluid itself, it is more a problem of the possible CTE mismatches between silicon and the materia used for containing the fluid).
 
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itsmydamnation

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Feb 6, 2011
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12:49PM EDT - Zen4 by end of 2022

Hmm Seems Zen4 is going to take ~24 Months instead of the established 15 months cadence.
Either that or they are just being purposefully vague as shown in the slides. Otherwise a bit long considering Papermaster mentioned concurrent teams working on the designs.
yeah as said else where , thats the standard way amd presents there road maps now ,

see looks like Zen3 only gets released end of this year.....

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zir_blazer

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Jun 6, 2013
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12:49PM EDT - Zen4 by end of 2022

Hmm Seems Zen4 is going to take ~24 Months instead of the established 15 months cadence.
Either that or they are just being purposefully vague as shown in the slides. Otherwise a bit long considering Papermaster mentioned concurrent teams working on the designs.
Urgh, this is pretty horrible. I think this is an indirect confirmation than we will have a Zen 3 with stacked Cache L3 (Warhol?) as a gap filler for around a year, since there is no other way around it. So, no consumer's guilt for anyone going Cezanne right now given than the next APUs are still far, far away.

I do believe than Genoa will be given launch priority over any consumer Zen 4 variants.
 
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eek2121

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Urgh, this is pretty horrible. I think this is an indirect confirmation than we will have a Zen 3 with stacked Cache L3 (Warhol?) as a gap filler for around a year, since there is no other way around it. So, no consumer's guilt for anyone going Cezanne right now given than the next APUs are still far, far away.

I do believe than Genoa will be given launch priority over any consumer Zen 4 variants.

Zen 3 with V-cache provides the performance uplift of an entire new architecture. AMD showed a few games, but nearly all workloads see considerable uplift.
 

Mopetar

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Jan 31, 2011
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Seems odd to slot in a Zen3D product that probably won't launch in any appreciable volume until early next year that will be refreshed in under 12 months going by AMD's schedule.

Assuming a more optimistic launch of Zen 4 around this time next year then AMD is really giving that a short life as a product.

Given that AMD still has a lot of the product stack to fill in with Zen 3, it would be surprising if they launched these as anything other than some special Ryzen 5000 parts. Something similar to the XT parts that Zen 2 used as an update/refresh towards the end of the cycle.
 

Timorous

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Seems odd to slot in a Zen3D product that probably won't launch in any appreciable volume until early next year that will be refreshed in under 12 months going by AMD's schedule.

Assuming a more optimistic launch of Zen 4 around this time next year then AMD is really giving that a short life as a product.

Given that AMD still has a lot of the product stack to fill in with Zen 3, it would be surprising if they launched these as anything other than some special Ryzen 5000 parts. Something similar to the XT parts that Zen 2 used as an update/refresh towards the end of the cycle.

I disagree.

DDR5 will be expensive for a while. Having a DDR4 platform that can compete with Alder for a lower / comparable platform cost and a DDR5 platform that costs more but is faster overall seems like a good way to handle the transition without needing to support both memory standards with a single platform.
 

zir_blazer

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Jun 6, 2013
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Seems odd to slot in a Zen3D product that probably won't launch in any appreciable volume until early next year that will be refreshed in under 12 months going by AMD's schedule.

Assuming a more optimistic launch of Zen 4 around this time next year then AMD is really giving that a short life as a product.

Given that AMD still has a lot of the product stack to fill in with Zen 3, it would be surprising if they launched these as anything other than some special Ryzen 5000 parts. Something similar to the XT parts that Zen 2 used as an update/refresh towards the end of the cycle.
Alder Lake is supposed to launch before the end of this year, while Zen 4 is more than a year away. Assuming than Alder Lake is good enough, the only emergency product that AMD has available to not lose its momentum is precisely, Cache stacked Zen 3, otherwise AMD risk to be under the shadow of Alder Lake for a whole year. Doesn't seems like a good plan to let that happen.
I suppose that we will have news about that right after Intel launches Alder Lake.
 
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Mopetar

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DDR5 will be expensive for a while. Having a DDR4 platform that can compete with Alder for a lower / comparable platform cost and a DDR5 platform that costs more but is faster overall seems like a good way to handle the transition without needing to support both memory standards with a single platform.

Zen 3 with or without 3D cache will still be good enough for that.

Alder Lake is supposed to launch before the end of this year, while Zen 4 is more than a year away. Assuming than Alder Lake is good enough, the only emergency product that AMD has available to not lose its momentum is precisely, Cache stacked Zen 3, otherwise AMD risk to be under the shadow of Alder Lake for a whole year.

Supposing Intel actually tops AMD across their full product stack, which may not be as easy as you think, how much is it going to beat AMD by?

If it's something like 5% is AMD really living under the shadow of Alder Lake? Weren't they living under an even greater shadow with Zen, Zen+, and Zen 2 in that case? However did they survive those dark times?
 

Abwx

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Apr 2, 2011
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Zen 3 with V-cache provides the performance uplift of an entire new architecture. AMD showed a few games, but nearly all workloads see considerable uplift.

Perhaps for things like 7Zip or Winrar and any other things memory speed/latency dependant but for things FP like Cinema 4D, Vray, 3DS Max and such softs there will surely be little difference.

That could make sense if gamers are targeted but not sure that they are a majority of the buyers.
 

Ajay

Lifer
Jan 8, 2001
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It all depends on pricing, both for AMD's Ryzen 5xxx series and Intel's Adler Lake CPUs. If Intel has an advantage, AMD has the option of reducing Prices to remain attractive if necessary. Then the V3D skus can occupy the top price points in their in their CPU portfolio. Worst case, Intel has an edge, and AMD suffers a small reduction in gross margins. Of course, we are getting ahead of ourselves, as Adler Lake isn’t on the market and hasn’t been reviewed. Competition will, as usual, be in all our interests. Otherwise, prices will keep spiraling upwards. It’s too bad that AMD is still capacity limited.
 
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moinmoin

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Seems odd to slot in a Zen3D product that probably won't launch in any appreciable volume until early next year that will be refreshed in under 12 months going by AMD's schedule.

Assuming a more optimistic launch of Zen 4 around this time next year then AMD is really giving that a short life as a product.

Given that AMD still has a lot of the product stack to fill in with Zen 3, it would be surprising if they launched these as anything other than some special Ryzen 5000 parts. Something similar to the XT parts that Zen 2 used as an update/refresh towards the end of the cycle.
I think we can consider Zen+, Zen 2 XT and Zen 3D all as plan Bs that AMD would market as a quasi new gen whenever the actual new gen takes longer.
  • Zen 2 on 7nm took longer after GloFo abandoned leading edge nodes so Zen+ slot in smoothly.
  • Zen 3 despite heavy shortage arrived smoothly so the Zen 2 XT chips were quickly forgotten.
  • It's still up in the air how Zen 4 will fare as that also depends on DDR5. In the meantime Zen 3D can slot in without AMD having to get all sweaty about the potential market circumstances.
 
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