AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache

Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by karamanolev on Thursday January 05, 2023 @05:37PM (#34267915)

Are you saying that 2x32GB is the max that allows for EXPO/XMP? I'm thinking about building a system like that and this is critical. Do you have any better resources that explore this more and test out different configurations?

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Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by skirmish on Thursday January 05, 2023 @06:35PM (#34268583)

That's my understanding, yes. All my knowledge is from random Reddit threads however.

Since I was scared off 128 GB by all those complaints, I built a 7950X system with 2*32GB memory, and it runs well/stable at its rated 6000 MT/s with EXPO on (also, AMD says 6000 MT/s is the sweet spot for AM5 memory interface, so I am happy).

Motherboard: ASRock X670E Steel Legend

RAM: G.Skill Trident Z5 Neo 64 GB (2 x 32 GB) DDR5-6000 CL30

Here is another thread I remember reading: https://old.reddit.com/r/hardware/comments/za0x0q/level1tech...

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Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by injinj on Thursday January 05, 2023 @10:49PM (#34270731)

That's what I got (7950x steel legend), except that I'm running 128GB memory at 4800.

Here's my stream results (with the cpu in 105watt "eco" mode):

  $ wget https://www.cs.virginia.edu/stream/FTP/Code/stream.c
  $ gcc -O3 -fopenmp stream.c
  $ a.out

  Number of Threads counted = 32

  Copy:           45571.7
  Scale:          40672.0
  Add:            45317.3
  Triad:          42759.0

With array size 8,000,000

  Copy:           31551.3
  Scale:          30983.7
  Add:            34403.6
  Triad:          34484.1

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Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by skirmish on Friday January 06, 2023 @12:11AM (#34271230)

Interesting, didn't think memory speed will make so much difference but it did.

7950x X670E Steel Legend, standard mode, 2*32 GB = 64 GB RAM at 6000, CL 30.

    Array size = 1,000,0000

    Copy:           61488.8
    Scale:          55905.4
    Add:            61320.2
    Triad:          57706.5

    Array size = 8,000,0000

    Copy:           43631.0
    Scale:          43062.7
    Add:            46782.6
    Triad:          46966.8

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Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by injinj on Friday January 06, 2023 @01:15AM (#34271589)

Wow, that's significant. I may have to look into that.

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Re:AMD Announces 7950X3D, 7900X3D Upto 128MB L3 Cache by wtallis on Thursday January 05, 2023 @06:46PM (#34268715)

Running with two DIMMs per channel is more challenging for the CPU's memory controller than one DIMM per channel, and it's much worse if they're dual-rank DIMMs—which current 32GB DDR5 modules are. I believe the EXPO/XMP profiles are all based on using only two DIMMs total, because those modules are sold in kits of two. At some point in the next year, there should be 24GB single-rank modules hitting the market, allowing for 48GB at top speed or 96GB with less of a performance penalty than 128GB from 4x32GB currently causes.

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