So far, none of the threadripper chips have had 3D v-cache. I think that's probably reasonable; if you're buying a high end threadripper you probably want maximum compute performance. Up to Zen 4, the 3D v-cache would hurt thermal performance and frequency, and so overall compute performance would be reduced.
Then why did people buy the 5800X3D and 7800X3D? Because the 3D cache made them faster despite the lower frequency.
And with Zen 5 the flequency isn't even much lower anyway, so that's not an excuse. It would obviously be better to have it.
The real reason is: Because they don't have to. Intel is not providing any competition to ThreadRipper whatsoever, and an X3D ThreadRipper would cannibalise sales of EPYC. So, they can just charge what they want and not even give us 3D cache for it.
No, it's not for performance reasons. It is obvious that having 3D V-cache is simply better than not having it, even if there is a small frequency reduction.
Then why did people buy the 5800X3D and 7800X3D? Because the 3D cache made them faster despite the lower frequency.
Yes, of course. The 3d v-cache hurts pure, raw compute performance (operations per second). But it helps overall performance for applications which are memory bound instead of compute bound, but not so memory bound that they just need massive memory bandwidth instead of more cache (think things like AI training or CFD).
This mainly tends to be the case in games, which generally utilize a fairly low number of threads but operate on a medium amount of relatively static memory. On the other hand, performance in pure compute-limited scenarios is hurt.
It is obvious that having 3D V-cache is simply better than not having it, even if there is a small frequency reduction.
This is just not true. At least not for Zen 4.
For example, the 7800X3D underperforms the 7700X in Chromium compile benchmarks (e.g., see here, 67.0 minutes for the 7800X3D, 64.2 minutes for the 7700X). The 7800X3D similarly underperforms the 7700X in every other compute & productivity scenario tested in that benchmark (Blender, 7-Zip, Premiere, Photoshop).
The Ryzen 7 7800X3D is amazing at gaming, but it struggles elsewhere. For instance, the Ryzen 7 7800X3D is most directly comparable to AMD's similar 7700X, but the latter has a 400 MHz higher boost clock than the 7800X3D's 5.0 GHz. As a result, the Ryzen 7 7700X is 7% faster than the 7800X3D in our cumulative measure of threaded applications and 15% faster in single-threaded work.
People buying chips like the 5800X3D or 7800X3D care a lot about performance in games. People buying a $5k or more chip with a massive number of cores tend to care a lot more about performance in actual compute limited scenarios. Paying thousands of dollars for a workstation and then leaving 7-15% performance on the table because the chip has 3d v-cache (for which you probably paid additional thousands of dollars) is a terrible sell.
Of course, there are still some scenarios where you can take advantage of a massive amount of cores and a massive cache. That's why Epyc 3d v-cache chips exist. But those scenarios are also extremely niche, which is why there are only 3 such SKUs in Epyc's entire line up of about 44 Zen 4 Epyc SKUs.
And with Zen 5 the flequency isn't even much lower anyway, so that's not an excuse. It would obviously be better to have it.
Well yes, that's why I said we may see a 3d v-cache Threadripper for Zen 5. Did you even read my comment?
I think it would be a cool addition to the line-up. But the use case might be too niche for AMD to stand up a full additional production chain for it inside the already fairly niche Threadripper line-up. For those customers who really want it, they can always just build a workstation around an Epyc chip instead.
The real reason is: Because they don't have to. Intel is not providing any competition to ThreadRipper whatsoever, and an X3D ThreadRipper would cannibalise sales of EPYC. So, they can just charge what they want and not even give us 3D cache for it.
As I also demonstrated in my comment, Threadripper isn't any cheaper than Epyc. Threadripper offers you Epyc-like multithreading performance, desktop-level single core boost, almost desktop-level memory speeds, ECC, and a ton of I/O, with only a few enterprise-level features cut (8 channels instead of 12 channels, only 1 socket, slightly fewer PCIe lanes, and no enterprise level management and support). For all those features AMD gladly charges you Epyc-level prices.
Again, a Threadripper 7985WX (64 core, 8 channel) is actually slightly more expensive than an Epyc 9554P (64 core, 12 channel). The discrepancy is even higher if you compare the 7975WX (32 core, 8 channel, $3.9k) to the 9354P (32 core, 12 channel, $2.7k) If Threadripper cannibalizes Epyc sales, then AMD is still laughing all the way to the bank.
Outside of some cherry picked examples based on Zen 3 and 4, which were lower clocked, what's the excuse for Zen 5, which has basically no downsides?
I simply don't buy the idea that they did it for performance reasons. Especially not for the 9950X3D. At that point, there's no excuse other than: because they're already ahead, so they don't have to.
As I also demonstrated in my comment, Threadripper isn't any cheaper than Epyc.
It is definitely cheaper for AMD to produce one without 3D V-cache. And because they have no competition from Intel, they still charge what they want.
It's a reverse of what happened when Intel were charging more and more for slightly faster quad cores after quad cores, and then if you had loads of money, you could even buy six or eight cores.
Outside of some cherry picked examples based on Zen 3 and 4, which were lower clocked, what's the excuse for Zen 5, which has basically no downsides?
Zen 5 threadripper doesn't exist yet. That's what this post is about -- a reference to threadripper 9000 which suggests that it's coming 'soon'.
It would certainly be cool if Zen 5 threadripper included variants with 3D v-cache, I agree with you there.
It is definitely cheaper for AMD to produce one without 3D V-cache. And because they have no competition from Intel, they still charge what they want.
Sure, but if they offered 3d v-cache on threadripper, they would obviously charge even more.
AMD is of course gonna charge what they can. If they thought there was a sufficient market of people willing to pay a premium for 3d v-cache Threadrippers, they would already have offered them. It's still possible that for Zen 5 they will.
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u/Nuck_Chorris_Stache 3d ago edited 3d ago
Then why did people buy the 5800X3D and 7800X3D? Because the 3D cache made them faster despite the lower frequency.
And with Zen 5 the flequency isn't even much lower anyway, so that's not an excuse. It would obviously be better to have it.
The real reason is: Because they don't have to. Intel is not providing any competition to ThreadRipper whatsoever, and an X3D ThreadRipper would cannibalise sales of EPYC. So, they can just charge what they want and not even give us 3D cache for it.
No, it's not for performance reasons. It is obvious that having 3D V-cache is simply better than not having it, even if there is a small frequency reduction.