[redox99]

That would be incredibly inefficient. The price difference of such a 128MB L3 + 0GB DRAM, compared to let's say 128MB L3 + 2GB DRAM would be quite small, and in practice the performance would be much much higher because realistically in your 128+0 setup you'll be wasting easily half of that on the OS or libraries data that isn't actually needed at the moment, whereas having DRAM you can actually use the whole 128MB of L3 for things that need to be fast.

It's also extremely niche to have a workload that requires such high CPU performance, but that it would fit including a linux OS in 128MB. Usually something like that is FPGA or DSP territory.

I think what you want is a cheap ARM CPU with DRAM stacked on top of it on the same package (which exists).