There are no command line parameters to worry about except the number of threads.
300 KH/s seems low for an 8 core @ 4 GHz, I get 575 on my i7-6700K.
Your CPU supports both AES and AVX so if the miner is properly compiled it should use the optimized hasher.
Just to confirm, did you download cpuminer-opt from here?
http://cryptomining-blog.com/7930-windows-binaries-for-the-cpuminer-opt-3-3-5-cpu-miner/Also what was displayed on start up regarding CPU capabilities and optimization? Post the output
if you can.
Yes, I downloaded it from that source, lol here is what it looks like right now while working... i'm using 7 cores instead of 8
https://ctrlv.cz/jWTG As you can see it is really sluggish but I have a wallet syncing in the background.
Here is the start screen
https://ctrlv.cz/Q9iLStartup looks good. Wallet synching can slow it down. Wait till that's done then close the wallet. Check your CPU usage
to make sure nothing else is taking time.