It's difficult to get solid figures. You have to determine what sort of computers they are (general processing power does not linearly translate to hashing power, does a supercomputer count as 'a computer' and - if so - do all dumbphones' processors also count?), how many are actually connected to the internet (no internet, no mining), how much of the the current estimated network hash rate is still from CPUs as it is, etc.
But we can go with some guesstimates as it pertains to your question in a more limited set. Let's on one hand ignore supercomputers and mobile phones and the like, and on the other hand pull an Oprah on the world and give everybody from newborns to just-about-to-croak a pretty decent CPU.
According to
wiki:Non-specialized hardware comparison, one of the fastest
consumer CPUs is the
Core i7 3930k with
6 processors yielding
66.6Mh/s.
Take 'consumer' with a big chunk of salt - most tech-savvy people may have a quad, more likely a dual, while there's still plenty of single-CPU machines out there in budget, business, etc. I specifically did not pick the 60-CPU Xeon, though.Now let's say that for every person in the world, there's one such computer. According to the
World Population Clock there's about 7.3 Billion people on Earth.
The total hash rate would thus be roughly 7,300,000,000 * 66,600,000hash/s = 486,180,000,000,000,000hash/s or 486,180Thash/s.
One current estimated network hash rate is 341,778.06Thash/s.
So, if everybody in the world had a quite decent computer to mine with, then they would exceed the current estimated network hash rate. Dropping the Oprah assumption, I think it's reasonable to guess that in terms of consumer (desktop/laptop) CPU power, it's nowhere close to the network hash rate - but 1% isn't unthinkable. And then there's GPUs.
That last linked site also provides a PetaFLOPS number we can run with: 4,340,581.31 . If we use that as a metric to get from PetaFLOPS to Thash/s - it's about 12,700:1 - and rolling with the 6.4 x 10^18 FLOPS number from 2011, that yields approximately 503Thash/s. So the computing power in the world would have to be 680 times greater now in order to match, or 6.8 times greater to get to 1% - again, not unthinkable if you do take into account all the smartphones, tablets, etc.
It really depends on what's going to count as 'CPU' here, but 1%? Quite possibly.
Then again, given how much more wasteful CPUs, GPUs and super computers are when compared to ASICs, it's moot in practice.
