Just signature and Merkle tree analysis of the whole blockchain (which is disabled by checkpoints) would take ~24+ hours of modern CPU processing power. These need to be performed by every user in a trustless environment. Optimizations are beneficial to every user, whether by utilization of available hardware resources, algorithmic shortcuts, or even hand-tuned x64/SSE assembly code routines.
It isn't so bad. On a i7 desktop ivy bridge 8-core machine, I could validate all the scripts up to block #295000 in just about 5 1/2 mn.
Succeeded #36249675
Failed #0
Elapsed 334s
I don't have a more recent bootstrap file, but by interpolating it shouldn't take more than 10 mn to do the complete chain.
Verification is disabled up to the most recent checkpoint, block 295000. The hash and headers leading to it is known trustworthy, so signature checking is turned off. That's what I said that you just quoted. If you remove all but the first checkpoint from chainparams.cpp and recompile, you will find a quite different result.
(295000, uint256("0x00000000000000004d9b4ef50f0f9d686fd69db2e03af35a100370c64632a983"))
BTW, you have 4 cores with hyperthreading, CPU-Z your machine. Still, a $300+ CPU is not the lowest bar.
