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>Ryzen 7940 supports up to 256Gb in a laptop form factor This is CPU-only RAM. It's way too low bandwidth to be used in high performance AI inference. The poin

>Ryzen 7940 supports up to 256Gb in a laptop form factor This is CPU-only RAM. It's way too low bandwidth to be used in high performance AI inference. The point with unified memory is that it's high bandwidth and available to the CPU, NPU, and GPU at the same time. It should beat the base M2. It's the highest-end AMD laptop chip compared to Apple's lowest end. However, I have doubts that the Ryzen 7940 has a faster GPU than the base M2. And of course, the M2 is significantly better in perf/watt.

timschmidt 3y ago
I'm not sure what you mean about CPU-only RAM, the Ryzen 7940 is an APU which integrates GPU and CPU and both draw from the same pool of ram, just like Apple silicon. Benchmarks seem to put the 7940 ahead of even the M2 Pro: https://www.cpubenchmark.net/compare/5454vs5189/AMD-Ryzen-9-7940HS-vs-Apple-M2-Pro-12-Core-3480-MHz https://www.cpubenchmark.net/compare/5454vs5189/AMD-Ryzen-9-... Performance per watt seems remarkably similar.
- senttoschool 3y ago
  >I'm not sure what you mean about CPU-only RAM, the Ryzen 7940 is an APU which integrates GPU and CPU and both draw from the same pool of ram, just like Apple silicon. Unified memory that is also high bandwidth. >Benchmarks seem to put the 7940 ahead of even the M2 Pro: Use Geekbench 6. It's closest to SPEC and optimizes well for both x86 and ARM. Performance per watt is significantly in favor of the M2.
  - timschmidt 3y ago
    > Unified memory that is also high bandwidth. I do think Apple is smart in using memory the way they are. It's the future. But AMD routinely posts higher performance numbers for CPU and GPU because their large caches boast similarly high memory bandwidth figures and AMD's cores have significantly higher IPC. I also think Apple's trick of extending the ARM ISA to allow for x86 style memory alignment is slick for fast emulation. Credit where it's due. Apple's caches are also very fast, just not as large as AMD's. In short, memory bandwidth is just one measurement of the bandwidth along the entire disk bandwidth <-> disk cache bandwidth <-> PCIe bandwidth <-> main memory bandwidth <-> L4 / L3 / L2 / L1 cache bandwidth hierarchy, and details about cache coherency, associativity, eviction strategies, branch prediction, and other sundries matter along the way. My 8 core Ryzen 5800x3D certainly compiles code a LOT faster than my 8 core M1 Mac despite the difference in main memory bandwidth. More memory is almost always going to mean that memory is slower, and Ryzen can handle more memory. Ryzen's architected with large caches and prefetching and all kinds of other goodies with that in mind. > Use Geekbench 6. It's closest to SPEC and optimizes well for both x86 and ARM. Geekbench is a synthetic benchmark. I'd prefer real workloads like compiling code or tokens / s inference.
    - senttoschool 3y ago
      >and AMD's cores have significantly higher IPC. This is most certainly wrong. Apple Silicon has way higher IPC. AMD chips clock much higher, which uses much more energy. Hence, Apple Silicon is much more efficient. >My 8 core Ryzen 5800x3D certainly compiles code a LOT faster than my 8 core M1 Mac despite the difference in main memory bandwidth. Code compilation is not bound by memory bandwidth. But AI training and inference is. Hence, we're talking about it. >Geekbench is a synthetic benchmark. I'd prefer real workloads like compiling code or tokens / s inference. You send me a link to a synthetic benchmark. All I did was link you to a better and more accurate one. Also, Geekbench performs real world workloads. You can easily look at individual scores for each test - besides the main score.
      - timschmidt 3y ago
        I looked around for AI specific benchmarks. Seems Openbenchmarking.org has quite a few. The 7940 is just making it's way onto the market, so I chose the closest desktop equivalent with a similar number of cores and memory bandwidth figures. Notably, the 7700 _does not_ have the AI acceleration cores of the 7940, meaning the 7940 will post much higher performance in that area. https://openbenchmarking.org/vs/Processor/Apple+M2,AMD+Ryzen+7+7700+8-Core https://openbenchmarking.org/vs/Processor/Apple+M2,AMD+Ryzen... Sure seems like the M2 is very far behind the 7700 in performance in all areas. Farther than can be explained by the difference in Mhz or package power.

timschmidt 3y ago

I'm not sure what you mean about CPU-only RAM, the Ryzen 7940 is an APU which integrates GPU and CPU and both draw from the same pool of ram, just like Apple silicon. Benchmarks seem to put the 7940 ahead of even the M2 Pro: https://www.cpubenchmark.net/compare/5454vs5189/AMD-Ryzen-9-7940HS-vs-Apple-M2-Pro-12-Core-3480-MHz https://www.cpubenchmark.net/compare/5454vs5189/AMD-Ryzen-9-... Performance per watt seems remarkably similar.

senttoschool 3y ago
>I'm not sure what you mean about CPU-only RAM, the Ryzen 7940 is an APU which integrates GPU and CPU and both draw from the same pool of ram, just like Apple silicon. Unified memory that is also high bandwidth. >Benchmarks seem to put the 7940 ahead of even the M2 Pro: Use Geekbench 6. It's closest to SPEC and optimizes well for both x86 and ARM. Performance per watt is significantly in favor of the M2.
- timschmidt 3y ago
  > Unified memory that is also high bandwidth. I do think Apple is smart in using memory the way they are. It's the future. But AMD routinely posts higher performance numbers for CPU and GPU because their large caches boast similarly high memory bandwidth figures and AMD's cores have significantly higher IPC. I also think Apple's trick of extending the ARM ISA to allow for x86 style memory alignment is slick for fast emulation. Credit where it's due. Apple's caches are also very fast, just not as large as AMD's. In short, memory bandwidth is just one measurement of the bandwidth along the entire disk bandwidth <-> disk cache bandwidth <-> PCIe bandwidth <-> main memory bandwidth <-> L4 / L3 / L2 / L1 cache bandwidth hierarchy, and details about cache coherency, associativity, eviction strategies, branch prediction, and other sundries matter along the way. My 8 core Ryzen 5800x3D certainly compiles code a LOT faster than my 8 core M1 Mac despite the difference in main memory bandwidth. More memory is almost always going to mean that memory is slower, and Ryzen can handle more memory. Ryzen's architected with large caches and prefetching and all kinds of other goodies with that in mind. > Use Geekbench 6. It's closest to SPEC and optimizes well for both x86 and ARM. Geekbench is a synthetic benchmark. I'd prefer real workloads like compiling code or tokens / s inference.
  - senttoschool 3y ago
    >and AMD's cores have significantly higher IPC. This is most certainly wrong. Apple Silicon has way higher IPC. AMD chips clock much higher, which uses much more energy. Hence, Apple Silicon is much more efficient. >My 8 core Ryzen 5800x3D certainly compiles code a LOT faster than my 8 core M1 Mac despite the difference in main memory bandwidth. Code compilation is not bound by memory bandwidth. But AI training and inference is. Hence, we're talking about it. >Geekbench is a synthetic benchmark. I'd prefer real workloads like compiling code or tokens / s inference. You send me a link to a synthetic benchmark. All I did was link you to a better and more accurate one. Also, Geekbench performs real world workloads. You can easily look at individual scores for each test - besides the main score.
    - timschmidt 3y ago
      I looked around for AI specific benchmarks. Seems Openbenchmarking.org has quite a few. The 7940 is just making it's way onto the market, so I chose the closest desktop equivalent with a similar number of cores and memory bandwidth figures. Notably, the 7700 _does not_ have the AI acceleration cores of the 7940, meaning the 7940 will post much higher performance in that area. https://openbenchmarking.org/vs/Processor/Apple+M2,AMD+Ryzen+7+7700+8-Core https://openbenchmarking.org/vs/Processor/Apple+M2,AMD+Ryzen... Sure seems like the M2 is very far behind the 7700 in performance in all areas. Farther than can be explained by the difference in Mhz or package power.