AMD launches first Zen 4 V-Cache models; Ryzen 7950X3D.

Colstan

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AMD has just launched their first Zen 4 CPUs with V-Cache, the 7950X3D and 7900X3D. It is notable that the 7800X3D won't ship until April 6th.

Relevant specs:

7950X3D: 16C/32T, 128GB L3, 4.2Ghz, Boost to 5.7Ghz.
7900X3D: 12C/24T, 128GB L3, 4.4Ghz, Boost to 5.6Ghz.
7800X3D: 8C/16T, 96GB L3, 4.2Ghz, Boost to 5.0Ghz.

Pricing for the models are $699, $599, and $449 USD, respectively. This is between a $100 to $180 premium over the non-X3D models.

AMD only sent out samples of the 7950X3D to reviewers. As usual, Gamer's Nexus had the most comprehensive review.



The 7950X3D and 7900X3D ship with the L3 connected to the left CCD, meaning that only half the cores can directly take advantage of that feature. In the video, Steve calls the launch date and performance of the 7950X3D and 7900X3D "suspect", because the 7800X3D has been delayed for another five weeks. All of the cores in the 7800X3D are able to fully utilize the added L3 without latency issues.

The CCD with access to the L3 runs at a lower clock than those in the other CCD. The cores without V-Cache can still access the L3, but incur a latency crossing the fabric, which AMD has attempted to work with Microsoft on improving. It's also important to enable AMD's extra driver features, or else performance will suffer. At full all-core load, the 7950X consumes 156W, compared to the 13900K's 295W.

On top of that, by disabling half the cores, they found that they actually get better performance. Along those lines, Hardware Unboxed "simulated" a 7800X3D in their review. Keep in mind that this isn't actual shipping silicon, and just a way for them to estimate the performance of the 7800X3D.



In terms of actual games, CPU heavy titles like Shadow of the Tomb Raider see up to a 25% uplift. With GPU intensive games, like Cyberpunk, the gains are negligible, and you really need a 4090 to see any benefit. There are outliers, like CSGO, which perform worse than the base 7950X.

Concerning content creation and non-gaming tasks, the V-Cache models see little to no benefit.

The delay in releasing the 7800X3D is certainly questionable. I think it stands to reason that AMD is trying to see how many customers are willing to pony up the cabbage for one of the more expensive models, before the 7800X3D ships. The 7800X3D model being the one that every gamer would likely purchase.

I think it would have been better to market the high core count models toward content creators which also happen to game. If AMD were being honest about this, they should launch them all at the same time. Instead, they are trying to market all three as gaming CPUs, even though games don't take advantage of the higher core count.

Also, AMD gimped the clock boost by 700Mhz between the 7950X3D and 7800X3D. Reviewers speculate this is a way of segmenting the line, in order to justify the existence of the higher end models.

My take is that if you are using these for non-gaming tasks, then it's a hard pass. If you are a gamer, wait for the 7800X3D model coming in April.
 

exoticspice1

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look the efficiency of the X3D zen4 parts. They destroy intel in perf/w. https://www.techpowerup.com/review/amd-ryzen-9-7950x3d/24.html
Like you said, you can also disable the cores to make it a 8/16 cpu and enable them back in content creation.

Intel again dies, ;)

1677545518334.png


Factorio and MS2020 FS also gain huge with cores disabled.
 

theorist9

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AMD has just launched their first Zen 4 CPUs with V-Cache, the 7950X3D and 7900X3D. It is notable that the 7800X3D won't ship until April 6th.

Relevant specs:

7950X3D: 16C/32T, 128GB L3, 4.2Ghz, Boost to 5.7Ghz.
7900X3D: 12C/24T, 128GB L3, 4.4Ghz, Boost to 5.6Ghz.
7800X3D: 8C/16T, 96GB L3, 4.2Ghz, Boost to 5.0Ghz.

Pricing for the models are $699, $599, and $449 USD, respectively. This is between a $100 to $180 premium over the non-X3D models.

AMD only sent out samples of the 7950X3D to reviewers. As usual, Gamer's Nexus had the most comprehensive review.



The 7950X3D and 7900X3D ship with the L3 connected to the left CCD, meaning that only half the cores can directly take advantage of that feature. In the video, Steve calls the launch date and performance of the 7950X3D and 7900X3D "suspect", because the 7800X3D has been delayed for another five weeks. All of the cores in the 7800X3D are able to fully utilize the added L3 without latency issues.

The CCD with access to the L3 runs at a lower clock than those in the other CCD. The cores without V-Cache can still access the L3, but incur a latency crossing the fabric, which AMD has attempted to work with Microsoft on improving. It's also important to enable AMD's extra driver features, or else performance will suffer. At full all-core load, the 7950X consumes 156W, compared to the 13900K's 295W.

On top of that, by disabling half the cores, they found that they actually get better performance. Along those lines, Hardware Unboxed "simulated" a 7800X3D in their review. Keep in mind that this isn't actual shipping silicon, and just a way for them to estimate the performance of the 7800X3D.



In terms of actual games, CPU heavy titles like Shadow of the Tomb Raider see up to a 25% uplift. With GPU intensive games, like Cyberpunk, the gains are negligible, and you really need a 4090 to see any benefit. There are outliers, like CSGO, which perform worse than the base 7950X.

Concerning content creation and non-gaming tasks, the V-Cache models see little to no benefit.

The delay in releasing the 7800X3D is certainly questionable. I think it stands to reason that AMD is trying to see how many customers are willing to pony up the cabbage for one of the more expensive models, before the 7800X3D ships. The 7800X3D model being the one that every gamer would likely purchase.

I think it would have been better to market the high core count models toward content creators which also happen to game. If AMD were being honest about this, they should launch them all at the same time. Instead, they are trying to market all three as gaming CPUs, even though games don't take advantage of the higher core count.

Also, AMD gimped the clock boost by 700Mhz between the 7950X3D and 7800X3D. Reviewers speculate this is a way of segmenting the line, in order to justify the existence of the higher end models.

My take is that if you are using these for non-gaming tasks, then it's a hard pass. If you are a gamer, wait for the 7800X3D model coming in April.


Here's my understanding from a quick review of the video. Is this right?:

1) V-cache (the special cache featured on the X3D models) improves gaming performance but is temperature-sensitive, which is why it needs to be put on lower-clocked cores. At the same time, AMD wanted this chip to also work well for non-gaming tasks, so it added an equal number of higher-clocked cores without V-cache.

2) The Windows scheduler can't distinguish the cores with V-cache and those without, so if all cores are active it ends up putting gaming thread(s) on the higher-clocked (and thus lower-performing, for gaming) cores, causing gaming performance to suffer. To avoid this problem, AMD parks the non-gaming (higher clocked) cores when a game is detected.

3) The upcoming 7800X3D has only half the cores of the 7950X3D. If all of these are gaming cores, then it could provide the same gaming performance as the 7950X3D for a much lower price (unless AMD deliberately gimps the 7800X3D in other ways).
 
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Colstan

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Here's my understanding from a quick review of the video. Is this right?:

1) V-cache (the special cache featured on the X3D models) improves gaming performance but is temperature-sensitive, which is why it needs to be put on lower-clocked cores. At the same time, AMD wanted this chip to also work well for non-gaming tasks, so it added an equal number of higher-clocked cores without V-cache.
To my knowledge, AMD hasn't explained why the V-Cache models are more sensitive to higher clocks. The previous model, the 5800X3D didn't feature any overclocking at all. You are correct about adding extra cores for non-gaming tasks.
2) The Windows scheduler can't distinguish the cores with V-cache and those without, so if all cores are active it ends up putting gaming thread(s) on the higher-clocked (and thus lower-performing, for gaming) cores, causing gaming performance to suffer. To avoid this problem, AMD parks the non-gaming (higher clocked) cores when a game is detected.
Right. AMD is also still working with Microsoft on the scheduler, so perhaps there will be a more elegant solution in the future.
3) The upcoming 7800X3D has only half the cores of the 7950X3D. If all of these are gaming cores, then it could provide the same gaming performance as the 7950X3D for a much lower price (unless AMD deliberately gimps the 7800X3D in other ways).
Hence the 7800X3D is the one that most gamers are going to want. AMD is trying to score as many sales on the two higher-end models before releasing the most affordable model in April. The primary differentiator is that the 7800X3D has a 700Mhz lower boost clock than the 7950X3D.
 

diamond.g

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To my knowledge, AMD hasn't explained why the V-Cache models are more sensitive to higher clocks. The previous model, the 5800X3D didn't feature any overclocking at all. You are correct about adding extra cores for non-gaming tasks.

Right. AMD is also still working with Microsoft on the scheduler, so perhaps there will be a more elegant solution in the future.

Hence the 7800X3D is the one that most gamers are going to want. AMD is trying to score as many sales on the two higher-end models before releasing the most affordable model in April. The primary differentiator is that the 7800X3D has a 700Mhz lower boost clock than the 7950X3D.
I think the 700Mhz boost comes from CCD1 on the 7950X3d which is missing from the 7800X3d. If you believe the Tomshardware link below coupled with the slide deck that AMD has released, it looks like the 7800x3d (CCD0) is only down 250MHz on the 7900x3d (single core boost) and they haven't said what the base clock is for the 7800x3d yet but I suspect it would be at worse 4GHz.

Tomshardware Look at the X3D line
 
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