But still, when you cpu mine at a couple dozen Mh/s, you're still vastly outnumbered against a multi Terrahash/second asic that's also mining at the same difficulty.
It is obvious, that you have to prepare some blocks in advance (for example in testnet3, you have everything filled, up to 2 hours in the future). And then, it is more related to network connections, than to the computing power. You just prepare a block, and you have your block with difficulty one, vs some ASIC block, also with difficulty one. Then, it is not about "who will mine it faster", but rather about "who will propagate it faster".
And of course, ASIC miners rule that world of test chains, so you have to mine your blocks around theirs. But still, it is possible to propagate some block faster, than some ASIC will do, because both players will prepare them in advance, and then the competition is related only to network connections.
Another thing is that ASIC miners potentially could always reorg CPU-mined blocks, but for some reason they don't. It is more profitable to mine a strong, regular block on top of them, because then, you can pick any block time you want. In case of CPU block times, it is more restricted.
i tested out the cpuminer that i included into my image for 2 weeks to see if it was stable, and i did not solve a single block...
It should mine at least some blocks, but they probably were reorged. If that's the case, then you have to improve the code for your node, not for your mining equipment. For example, to mine testnet blocks easily, I slighttly modified Bitcoin Core, and since then, it works on my CPU.
So yes, maybe at the moment it might be possible to mine a couple testnet4 blocks with your cpu if you're really lucky.
I repeated the same thing on testnet3, just to be sure. Now, I can mine on CPU in both networks, but testnet4 is more stable. However, mining in testnet3 is still quite good idea, if you want to test block rewards, based on transaction fees.
