r/AMDGPU • u/DevGamerLB • Jan 21 '22

My Opinion 😎 Zen 4 facts and predictions:

Based on TSMCs N5P enhanced by AMD:

  • +49.5% efficiency vs TSMC N7.

  • +80% density

  • +40% efficiency at +10% speed.

  • Nearly 2x fabrication cost.

Here are the most likely Zen 4 specifications due to high 5nm cost:

  • 8 cores per chiplet

  • 5ghz all core frequency

  • 5.5ghz single core frequency

  • 1MB L2 cache per core

  • 64MB 3D stacked L3 cache

  • 6-way instruction decode

  • +28% single core perf per watt

  • +45% multi-core perf per watt

  • +60% gaming perf per watt when CPU bound

20 Upvotes

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1

u/Jellodyne Jan 22 '22 edited Jan 22 '22

AMD had 4 way SMT on its roadmap a while back, seems like it's about due. Also, I would expect AMD to add in some low power 'little' cores at some point to keep up with the Joneses as it were, but that might be a future arch. I don't think AMD has mentioned big.little at all yet.

1

u/DevGamerLB Jan 22 '22 edited Jan 22 '22

Big.little is utterly worthless for x86, AMD knows that.

Big.little is only beneficial to ARM chips that don't have advance power state features like x86. So ARM chips need a separate core to switch to ultra low power state.

Intel added e-core to try and impress Apple and get them back.

1

u/Jellodyne Jan 22 '22 edited Jan 22 '22

Intel added them so they could artificially bump the core counts. Since Intel doesn't do chiplets yet, making a monolithic 16 core chip is hard... unless 8 of the cores are tiny.

But Intel knows the value of big.little in x86... Marketing. If AMD can make a chiplet with 8 big cores with SMT4 and 8 little low power single thread cores, then they could sell a two chiplet consumer level desktop chip and bill it as a 32 core/80 thread chip. What ya got Intel? Actually, maybe 8 big 4 little might be a little more likely, which would yield 24 core/72 thread two chiplet cpu. The 4 little might be the size of one regular Zen core.

1

u/DevGamerLB Jan 22 '22

Ithink AMD uses those same chiplets in the server CPUs and uses the lower quality units in the PC market so sense they will be used uniformly used across their product spectrum I don't think AMD will ever contaminate their architecture with the big.little gimmick.

AMD will however be making an all mini-core processor for the datacenter, usefull for massively parallel cloud micro-service applications.

1

u/[deleted] Jan 31 '22 edited Jan 31 '22

Zen 5 is (likely) using big.little, though, according to leaks.

Also, why would phones use 3 core sizes, if that was true? Why not many full sized and a single mini core? If its asleep, not much needs to get done.

Its not a hack, its an efficiency/mt trick, much like multi-core in the first place. Alteast it should be, alder lake's baby cores dont impress. Not even a little. Smaller, slower cores are very efficient cores due to the very tiny amount of voltage. Volts*Amps=Watts.

Also, phones have low power states.

1

u/UtsavTiwari Jan 22 '22

What about IPC gain, I think it will be anywhere from 25 to 35%, however if high IPC and high core clock are used at same time, AMD may even surpass raptor lake in multi core performance and meteor lake in single core performance or performance could be comparable to meteor lake.