Which would be the best for mining XMR:
1. Upgrading to an i7 that support 8 threads
2. Purchase a GTX1060 GPU
Almost in the same price range.
Any tips would be much appreciated!
Depends on some factors: how much is your electricity? How cool is your climate? How much noise can you tolerate?
A CPU will tend to be more efficient. That said, check the L2 cache of the i7. Each mining thread needs 2 MB cache. So, even if you have 8 threads, if you only have 6 MB cache, your going to mine with 3 threads, maybe 4.
That said, I know the new skylakes can do 60 hashes / second on 1 thread.
Pentium(R) CPU G4400 @ 3.30GHz
I thought it was 2MB of L3 cache per mining thread not L2.
I remember digging into this at one point and the conclusion I came to was that its whatever the largest cache on-chip is. AFAIK, these caches are essentially just memory on the CPU itself to effect the highest speed, and the different cache levels relate to speed and priority... so its not like cryptonite is seeking out the L3 cache specifically to store the scratchpad to perform the PoW, its just going "hey you sloppy sons ah bitches I need to dump some shit in memory." Why cryptonite is a drunken sailor I have no idea. So the CPU dumps this to whatever memory it can. I assume it first goes to L1 cache and L1 cache is like "Please go elsewhere. L1 is reserved for the finest of processes" as it turns its nose up on the cryptonite PoW, cause aint no way L1 has 2 MB. Then it gets to L2 and its like "you gots some room for my pad?" and L2 goes "sure", because its a processor with a large L2. Yada yada yada, down the chain.
In the case that none of caches had the 2 MB space, cryptonite can still work, its just incredibly slow because the stuff has to go all the way from the CPU to the (gasp) memory, which is like Bourbon street for processes. And maybe you'll make it down to that crazy ass old tavern at the end of the strip.
wow, thanks so much @gingerale - I really appreciate your detailed feedback! Think I will look into an i& with as much L2 cache as I can find.