Friday, April 5th 2024

AMD Zen 5 Execution Engine Leaked, Features True 512-bit FPU

AMD "Zen 5" CPU microarchitecture will introduce a significant performance increase for AVX-512 workloads, with some sources reported as high as 40% performance increases over "Zen 4" in benchmarks that use AVX-512. A Moore's Law is Dead report detailing the execution engine of "Zen 5" holds the answer to how the company managed this—using a true 512-bit FPU. Currently, AMD uses a dual-pumped 256-bit FPU to execute AVX-512 workloads on "Zen 4." The updated FPU should significantly improve the core's performance in workloads that take advantage of 512-bit AVX or VNNI instructions, such as AI.

Giving "Zen 5" a 512-bit FPU meant that AMD also had to scale up the ancillaries—all the components that keep the FPU fed with data and instructions. The company therefore increased the capacity of the L1 DTLB. The load-store queues have been widened to meet the needs of the new FPU. The L1 Data cache has been doubled in bandwidth, and increased in size by 50%. The L1D is now 48 KB in size, up from 32 KB in "Zen 4." FPU MADD latency has been reduced by 1 cycle. Besides the FPU, AMD also increased the number of Integer execution pipes to 10, from 8 on "Zen 4." The exclusive L2 cache per core remains 1 MB in size.
Update 07:02 UTC: Moore's Law is Dead reached out to us and said that the slide previously posted by them, which we had used in an earlier version of this article, is fake, but said that the information contained in that slide is correct, and that they stand by the information.
Source: Moore's Law is Dead (YouTube)
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63 Comments on AMD Zen 5 Execution Engine Leaked, Features True 512-bit FPU

#51
JohH
I'll say it again: we don't know how they implemented 512-bit operations. It could be fused fp0/fp1 and fused fp2/fp3. In which case it wouldn't be using any extra area but would still be able to do 512-bit operations in a single cycle instead of sequentially in two cycles like Zen 4.

It is pre-emptive to cry about wasted area.
Posted on Reply
#52
oxidized
I don't understand how y'all might believe anything that comes out of the mouth of someone called "Moore Law is Dead"
Posted on Reply
#53
stimpy88
user556Oh, man, what a huge let-down. I had my hopes up it was the general instruction pipeline that was up by 40%. But alas not it seems.
You would have loved the Intel days! A 40% IPC uplift would have taken Intel 15 years! Each generation of "new" Intel CPUs had 1-3% IPC "improvements" back in the day, and many made claims that x86 had hit a performance wall, and no significant improvements could ever be made.

Thanks to AMD, all that is thankfully over now, although it seems Intel has gone back to just bumping clocks and "gluing" on more cores on again.
Posted on Reply
#54
ToTTenTranz
mahoneyYou are a bunch of idiots for taking MLID's leaks as truth
When the prick has a long track record of deleting all his BS leak videos when they don't come true.
I'm still pissed about him claiming with 100% certainty that Intel's GPU business was over and done just a month before the Arc GPUs were actually in the market. I remember that shit even making Intel's GPU engineers and marketing people uncomfortable.

One would think this would've been a career ending event to a leaker, but turns out his followers only grew in number since then. What the hell.
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#55
Denver
ToTTenTranzI'm still pissed about him claiming with 100% certainty that Intel's GPU business was over and done just a month before the Arc GPUs were actually in the market. I remember that shit even making Intel's GPU engineers and marketing people uncomfortable.

One would think this would've been a career ending event to a leaker, but turns out his followers only grew in number since then. What the hell.
Why? All the loss-making segments intel has either sold or abandoned, this is the current state of Intel's GPU business. It's a very logical prediction.
Posted on Reply
#56
SL2
bugThe more chips you turn them into, the lower the price.
..no, the lower the manufacturing COST. That doesn't mean that they'll lower the MSRP and the consumer will pay less.
Posted on Reply
#57
Redwoodz
R-T-BI've read it before. I know what Torvalds argues.

Have a quote:
Well, first off Intel's FPU performance has always been low.
The main difference now is you have AI. A use and justification for special instruction sets.
Posted on Reply
#58
Punkenjoy
You can't really compare some of 14 nm implementation of AVX 512 with Zen 5 implementation on 3nm nodes. Intel was probably asking too much from the 14nm +* nodes and that is why the performance for it was too low.


Denser process with less leakage allow you to design much more complex execution units. Those can perform better that the same clock and clock higher. It's one of the reason why cache size have stayed in the same ballpark.

I mean clawhammer (Athlon 64) had 1 MB of L2 in 2003. Cache are a cycle and it's what they put when they can't just put a beefier execution unit or front end.
Posted on Reply
#59
jigar2speed
SL2Who's cheering?
He meant to say, why people aren't enraged.
Posted on Reply
#61
TumbleGeorge
PhilaphlousI'm sure the shutdown at TSMC from the earthquakes will definitely impact AMD...Delay or reduced shipments if delivered on time...
I don't think so. Probably all ZEN 5 chips that need this year already got its lithography before earthquake.
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#62
Makaveli
phintsNot clear to me why they would put all that die realestate into AVX-512 when almost no one uses them outside game emulators, unelss there is some added push for AI workloads there that I don't know about since everyone is advertising that now.

Silly leaks aside this should finally be a very exciting year for HEDT CPUs.
Probably because its used in the Enterprise space so Eypc cpu's will need it. And consumer products are basically just cut down versions of those products.
Posted on Reply
#63
Technologov
DavenIsn’t there some AI / machine learning algorithms that can use AVX512 now?
Stockfish Chess.
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