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AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

arstechnica.com

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Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#81

Post by adrian_b »

Aurornis wrote: post #43
magicalhippo wrote: post #25

Probably fun for those who already bought DDR5 memory... still kicking myself for not just pulling the trigger on that 128GB dual stick kit I looked at for $600 back in September. Now it's listed at $4k... Meanwhile I hope my AM4 will chug along a few more years.

> Now it's listed at $4k... You can buy 128GB of DDR5-6000 with a 9950X3D (not this newest X2 version, but still a $699 CPU) and a motherboard and a case for $2800 right now: https://www.newegg.com/Product/ComboDealDetails?ItemList=Com... If you don't need 128GB, there are quality 64GB kits for under $700 on Newegg right now, which is cheaper than this CPU. If someone needs to build something now and can wait to upgr…

$2800 is still a huge price in comparison with the last year.

Last summer, a 9950X3D + motherboard + cooler + 128 GB DRAM + VAT sales taxes was the equivalent of $1400 in Europe, where I live.

That's half of your quoted price. That was without case and PSU, but adding e.g. $200 for those would not change much.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#82

Post by stingraycharles »

coppsilgold wrote: post #60
wmf wrote: post #24

Earlier quoted context omitted.

Context: Early in the firmware boot process the memory controller isn't configured yet so the firmware uses the cache as RAM. In this mode cache lines are never evicted since there's no memory to evict them to.

There may be server workloads for which the L3 cache is sufficient, would be interesting if it made sense to create boards for just the CPU and no memory at scale. I imagine for such a workload you can always solder a small memory chip to avoid having to waste L3 on unused memory and a non-standard booting process so probably not.

Most definitely, I work in finance and optimizing workloads to fit entirely in cache (and not use any memory allocations after initialization) is the de-facto standard of writing high perf / low latency code.

Lots of optimizations happening to make a trading model as small as possible.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#83

Post by amelius »

chao- wrote: post #4

Crazy to think that my first personal computer's entire storage (was 160MB IIRC?) could fit into the L3 of a single consumer CPU! It's probably not possible architecturally, but it would be amusing to see an entire early 90's OS running entirely in the CPU's cache.

640K ought to be enough for anybody.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#84

Post by adrian_b »

spockz wrote: post #61
EnPissant wrote: post #39

Earlier quoted context omitted.

It's very workload dependent. It certainly does more than 2% on many workloads. See https://www.phoronix.com/review/amd-ryzen-9-9950x3d-linux/10 > Here is the side-by-side of the Ryzen 9 9950X vs. 9950X3D for showing the areas where 3D V-Cache really is helpful: Coincidentally, it looks they filtered to all benchmarks with differences greater than 2%. The biggest speedup is 58.1%, and that's just 3d vcache on half th…

I think GP was saying that the additional 3D cache on this chip compared to the standard x3d isn’t going to do much. I’m curious to see whether the same benchmarks benefit again so greatly.

On AMD the L3 cache is partitioned between the 2 chiplets.

So for 9950X3D half of the cores use a small L3 cache.

For applications that use all 16 cores, the cases where X3D2 provides a great benefit will be much more frequent than for a hypothetical CPU where the same cache increase would have been applied to a unified L3 cache.

The threads that happen to be scheduled on the 2nd chiplet will have a 3 times bigger L3 cache, which can enhance their performance a lot and many applications may have synchronization points where they wait for the slowest thread to finish a task, so the speed of the slowest thread may have a lot of influence on the performance.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#86

Post by neRok »

stingraycharles wrote: post #35
throwaway85825 wrote: post #33

It's disappointing that they had this for years but didn't release it until now.

I think it’s mostly that they had leftover cache.

This video made the argument that AMD released it to not give Intel a look-in: [AMD KILLED Intel's 290K Dreams w/ R9 9950X3D2](https://www.youtube.com/watch?v=u7SyrDPbKls)

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#87

Post by adrian_b »

2001zhaozhao wrote: post #70

I don't really see a huge reason to buy this other than it being a top-tier halo product. For gaming, AMD already pins the game threads to the CCD with the extra cache pretty well. For multi-threaded workloads the gain from having cache on both CCDs is quite small.

The gain is very workload dependent, so there are no generally-applicable rules.

There are many applications which need synchronization between threads, so the speed of the slowest thread has a disproportionate influence on the performance.

In such applications, on X3D2 the slowest thread has a 3 times bigger cache on an X3D2 vs. X3D. That can make a lot of difference.

So there will be applications with no difference in performance, but also applications with a very large difference in performance, equal to the best performance differences shown by X3D vs. plain 9950X.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#88

Post by sundvor »

jmyeet wrote: post #52
magicalhippo wrote: post #25

Probably fun for those who already bought DDR5 memory... still kicking myself for not just pulling the trigger on that 128GB dual stick kit I looked at for $600 back in September. Now it's listed at $4k... Meanwhile I hope my AM4 will chug along a few more years.

After randomly breaking the AM4 CPU and motherboard in my 4 year old PC last year and seeing that at the time I'd spent almost a new PC to get new parts and rebuild it. Less if I wanted to do a complete rebuild myself but I'm over building PCs. I've done that for years. It was an expensive mistake as I bought a few options to experiment including a NUC and an M4 Mac Mini but eventually bought a 9800X3D 5070Ti PC for…

The C30 64GB kits are nearly impossible to buy now, so, well done. Got one in September '23 for ~$380 AUD, on the rare occasions it's available today it's been over $1600 AUD.

I upgraded my UPS to a sine interactive unit to minimise the risk of it dying to bad power while the market is so crazy...

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#89

Post by tarangsutariya »

magicalhippo wrote: post #25

Probably fun for those who already bought DDR5 memory... still kicking myself for not just pulling the trigger on that 128GB dual stick kit I looked at for $600 back in September. Now it's listed at $4k... Meanwhile I hope my AM4 will chug along a few more years.

Wonder how much sales amd and intel are losing because of tight DDR5 supply

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#90

Post by magicalhippo »

tarangsutariya wrote: post #89
magicalhippo wrote: post #25

Probably fun for those who already bought DDR5 memory... still kicking myself for not just pulling the trigger on that 128GB dual stick kit I looked at for $600 back in September. Now it's listed at $4k... Meanwhile I hope my AM4 will chug along a few more years.

Wonder how much sales amd and intel are losing because of tight DDR5 supply

I can't imagine it's looking good in the consumer space, but server space seems to be lit[1]:

Su said that typically, the first quarter (Q1) is slower due to seasonal patterns, but AMD has seen its data center business expand from Q4 into Q1, demonstrating ongoing strength across both CPUs and GPUs. This growth underscores the company’s ability to capitalize on rising demand for AI compute and enterprise workloads, even during traditionally quieter periods.

“We are going into a big inflection year here in 2026. The CPU business is absolutely on fire.”

[1]: https://stocktwits.com/news-articles/markets/equity/amd-ceo-...

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