Network hash rate

[Borph]

Sorry for maybe newbie question, but where does the network hash rate figures come from?

I like the graphs like here: http://bitcoin.sipa.be/

I do understand that clients accept block according to the difficulty which in turn is adjusted so that it's difficult enough to get blocks every 10 min.

I don't see how the current network hash rate can be determined down to the hour, I mean do nodes/miners report if or how fast they are mining? Or does sipa.be just plot the amount of found blocks per hour? But this would take already the difficulty into account, making it hard to tell the actual Ghash/s.

[1715212928]

1715212928

[1715212928]

1715212928

[1715212928]

1715212928

[grue]

I mean do nodes/miners report if or how fast they are mining?

no

Or does sipa.be just plot the amount of found blocks per hour? But this would take already the difficulty into account, making it hard to tell the actual Ghash/s.

correct. it's entirely estimated.

[Gigaminer]

I mean do nodes/miners report if or how fast they are mining?

no

Or does sipa.be just plot the amount of found blocks per hour? But this would take already the difficulty into account, making it hard to tell the actual Ghash/s.

correct. it's entirely estimated.

this is true.

[Borph]

But then, is sipa.be not collecting too much data to simplify again with averages?

I mean the difficulty is constant for a time frame, what varies is the number of blocks. The figure blocks/hour is about 6, so still too small. Blocks/day should be around 144, a better number to track. Maybe already combined with the current difficulty it would give one figure (in GHash/s or so) per day, much smaller database!