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Adept II

[SOLVED] What's the max Core count per Socket in the whole x86 architectures range ?

With the introduction of the EPYC with more than 32 Cores / 64 Threads, my project CoreFreq is impacted to face such a high number of CPUs.

Can we say than a 64 bits architecture is de facto limiting the number of physical Cores to 64 ?

Can we say than a 64 bits architecture preserve any memory atomic operation to a quad word ?

What is the most discriminant definition of 64 bits ? The size of the cache line queried from cpuid ?

Other thoughts ?

Impacted source code

I'm using asm atomic operations for several purposes:

  • bit-mask
  • threads synchronization

Where each CPU, based on its number, is assigned a bit location in quad-word. This allows simple atomic comparaisons for instance.

Issue: with a 128 SMT cores Processor, the 64 bits memory and register involved in atomic operations are not "long" enough to store all CPUs.

4 Replies
Big Boss

64bits supports up to 256 cores
64bits means that the cpu uses 64bit wide datapath, integer size and memory address widths

64-bit computing - Wikipedia 
Caps and Limits on Hardware Resources in Microsoft Windows and Red Hat Enterprise Linux – PADT, Inc.... 
qoute: "

Limits on Cores, RAM, and USERS by Operating System

  • Microsoft Windows Operating Systems
    • Windows 7
      • Professional / Enterprise / Ultimate
        • Processor: 2 Socket limit (many cores)
        • Core limits:
          • 64-bit: 256 max quantity of cores in 1 physical processor
          • 32-bit: 32 cores max quantity of cores in 1 physical processor
        • RAM: 192 GB limit to amount of accessible


PC: R7 2700X @PBO + RX 580 4G (1500MHz/2000MHz CL16) + 32G DDR4-3200CL14 + 144hz 1ms FS P + 75hz 1ms FS
Laptop: R5 2500U @30W + RX 560X (1400MHz/1500MHz) + 16G DDR4-2400CL16 + 120Hz 3ms FS

Thank you for these pointers.

I now have to find GP instructions with 256 bits operands that I can use in Kernel ...

Edit: so far, available for both AMD & Intel, the CMPXCHG16B instruction to compare RDX:RAX with m128.

Thus 128 CPUs

Journeyman III

It represents another attempt by the Arm world to grab a chunk of the lucrative data-center server market, which is virtually 100 per cent locked up by Intel and its x86-64 Xeon bruisers mywegmansconnect

Adept II

After searches, I'm closing subject with a 256 Core Count. Scaling CoreFreq up in progress ...