Not much, I guess. The original 8086 had only around 30000 transistors. The die of a modern quad-core Intel chip accommodates more than a billion transistors, a

Not much, I guess. The original 8086 had only around 30000 transistors. The die of a modern quad-core Intel chip accommodates more than a billion transistors, about half of which are dedicated to the GPU and maybe around 10% are taken by a single core. That would roughly translate to 100 million transistors per core (including their L1 and L2 caches), so the footprint of the legacy cruft should be negligible.