My desktop could easily handle 20 mb blocks, and it isn't anywhere near top of the line.
Does anyone know why current blocks take so much longer to download in Bitcoin Core than old blocks? As far I as know the increased difficulty is only related to mining and has nothing to with checking downloaded blocks.
Example: When I start a fresh installation of Bitcoin Core, it starts downloading the blockchain. It quickly goes through the first years with small blocks, then after that it's downloading with more than 2 MB/s continuously. That means at least 2 blocks per second (say 90 seconds to download 1 day's worth of blocks). But when it gets closer to the current date, it slows down.
Now when I start Bitcoin Core, it downloads fast for a bit, then stops, continues a bit later again, and then downloading stops entirely for a long time. CPU load is low, hard drive I can't hear (and I have no indicator LED). My question is: why is it so slow? Why can't it continue to download 2 MB/s so I can update 3 days in 5 minutes?
This also happens on a trimmed version of the blockchain, so it can't be caused by Bitcoin Core checking all transactions on disk. The only thing that also gets bigger in the trimmed version, is the chainstate directory (now 1.6 GB). Could that be what slows it down?
As another test, on my old Atom laptop, it updates 3 weeks blockchain in 2 calendar days. To come back to the statement I quoted: if blocks would be 20 times larger, and I extrapolate this, my old Atom couldn't keep up anymore. And if this gets worse in the future, it could become a limitation for faster hardware too.
While I've typed all this, Bitcoin Core running on my i3 still says "3 days behind", the same as when I started typing. Network activity has slowed down to just a few kB/s "background" level. What is it doing?