唔好意思miss咗你個comment
https://www.youtube.com/watch?v=sgfljXSgdj4
留意下面d comment, Timothy John Duffin,"........, many thanks for this guide! I managed to revive a mid 2010 iMac 21" using an Nvidia GTX 780m. I also went head and installed Mojave 10.14.5 using Dosdude1's patcher. "
https://www.ifixit.com/Answers/View/62989/Can+I+upgrade+my+CPU+on+iMac+from+i5-2500S+to+i7-2600
留意下面answers嘅CHOSEN SOLUTION, John,"I used regluar i7-2600, not unlocked "K" SKU. So, it should be "BX80623I72600". And now, as I'm using this setup for a week, I can just say that there is not difference in system behaviour. So, system fans are not spinning faster, machine is not noisier, it's 100% stable system."
IFIXIT其實都有instruction教人點整
https://www.ifixit.com/Device/iMac_Intel_21.5%22_EMC_2428