| > M3 ultra is obviously 1-2 generations behind and new the studio is expected 'any day now. M3 Ultra uses a 1024-bit memory bus, which is a major inconvenience to Apple because they're soldering everything. In ordinary systems if you have 16 memory slots and any one of the memory chips is bad, you replace that stick. If the processor is bad, you replace the processor. If the system board is bad, you transfer the processors and memory to another one. If any of those has a defect after you solder thousands of dollars worth of memory onto the same board as a >$1000 CPU, you're not doing well. Worse, the more memory chips you have and the more pins the CPU needs for its memory bus, the higher the chances of one of them having a defect. In addition to that, when you get to that number of pins it starts getting harder to run the memory at the highest speeds. The M3 uses DDR5-6400 but some of the M5 line is using DDR5-9600. It may or may not be possible to do that speed when using a 1024-bit bus -- not every existing M5 even does it. If it isn't then the Ultra wouldn't be much faster than the Max since it would have to use a lower memory speed. If it is then the tolerances would have to be even tighter and increase the defect rate even more. Which is to say, I can see why they haven't released an Ultra since the M3. > but get to use the GPU for compute so potentially faster than the EPYC. Only if the bottleneck is compute rather than memory bandwidth, and for LLMs it's generally memory bandwidth. And if something significant was compute bound, there are also higher core count CPUs. > Total Cost of Ownership in the Epyc is going to be WAY higher because of electricity costs, the EYPC is going to be consuming probably 5X the electricity and is probably not going to sit quietly on your desk The M3 Ultra has a 480W TDP. There are relevant EPYC SKUs on SP5 at 125-200W/socket. > you may find a model bigger than e.g 70b suddenly is bottlenecked by the CPUs or memory bandwidth The extra RAM allows you to fit the larger model in memory to begin with, without which it's pretty hopeless. The bottleneck typically is memory bandwidth for LLMs, but that's true pretty much regardless of the model size. Moreover, mixture of experts models require significantly more RAM for the same amount of compute/bandwidth. > you also need at least one NVME disk That's ~$100. > As you say, the thing is it's not 'however much memory you want' it's 24 sticks which at $300 a stick for 16GB is $7200 The chips don't cost a materially different amount based on whether you solder them. Apple presumably discontinued the 256GB and 512GB versions of the M3 Ultra because they'd have had to add a similar number to the price. |